Triangle Seminars
June 2026
Thu
4 Jun 2026
TBA
📍 London
Ida Zadeh
(Southampton)
Abstract:
TBA
TBA
Posted by: Nathan Moynihan
Wed
3 Jun 2026
TBA
📍 London
Claudia de Rham
(Imperial College)
Abstract:
TBA
TBA
Posted by: Gabriele Travaglini
May 2026
Thu
28 May 2026
TBC
📍 London
Ana-Maria Raclariu
(KCL)
Abstract:
TBC
TBC
Posted by: Kymani Armstrong-Williams
Thu
21 May 2026
TBC
📍 London
Graham Brown
(Edinburgh)
Abstract:
TBC
TBC
Posted by: Kymani Armstrong-Williams
Wed
20 May 2026
TBA
📍 London
Charlotte Sleight
(Durham)
Abstract:
TBA
TBA
Posted by: Andrew Svesko
Thu
14 May 2026
TBC
📍 London
Facundo Rost
(Scuola Normale Superiore)
Abstract:
TBC
TBC
Posted by: Kymani Armstrong-Williams
Thu
7 May 2026
TBC.
📍 London
Zizang Qiu
(Edinburgh)
Abstract:
TBC.
TBC.
Posted by: Kymani Armstrong-Williams
Wed
6 May 2026
TBA
📍 London
Thomas Mertens
(Ghent University)
Abstract:
TBA
TBA
Posted by: Andrew Svesko
April 2026
Thu
30 Apr 2026
TBC.
📍 London
Fabrizio Caola
(Oxford)
Abstract:
TBC.
TBC.
Posted by: Kymani Armstrong-Williams
Wed
29 Apr 2026
Inspiral-merger-ringdown waveforms from gravitational self-force theory
📍 London
Lorenzo Kuchler
(University of Southampton)
Abstract:
Compact binaries with asymmetric mass ratios are key expected sources for next-generation gravitational-wave detectors. Gravitational self-force theory has been successful in producing post-adiabatic waveforms that describe the quasicircular inspiral around a nonspinning black hole with sub-radian accuracy, in remarkable agreement with numerical relativity simulations. Current self-force models, however, break down at the innermost stable circular orbit (ISCO), missing the final merger and ringdown stages. In this talk, I will show how the self-force waveforms can be extended beyond the ISCO, building first-principles inspiral-merger-ringdown waveforms. I will then dissect the final merger-ringdown waveforms and compare them with a self-consistently calculated sum over quasinormal modes and a stationary-phase approximation. Finally, I will briefly discuss how beyond-GR effects can be modularly added in this framework.
Compact binaries with asymmetric mass ratios are key expected sources for next-generation gravitational-wave detectors. Gravitational self-force theory has been successful in producing post-adiabatic waveforms that describe the quasicircular inspiral around a nonspinning black hole with sub-radian accuracy, in remarkable agreement with numerical relativity simulations. Current self-force models, however, break down at the innermost stable circular orbit (ISCO), missing the final merger and ringdown stages. In this talk, I will show how the self-force waveforms can be extended beyond the ISCO, building first-principles inspiral-merger-ringdown waveforms. I will then dissect the final merger-ringdown waveforms and compare them with a self-consistently calculated sum over quasinormal modes and a stationary-phase approximation. Finally, I will briefly discuss how beyond-GR effects can be modularly added in this framework.
Posted by: Riccardo Gonzo
Wed
29 Apr 2026
Non-invertible symmetries of higher-dimensional QFTs act (almost) invertibly on local operators
📍 London
Rajath Radhakrishnan
(Oxford)
Abstract:
Symmetries of a quantum field theory are implemented by topological operators. These are special extended operators whose correlation functions are insensitive to continuous deformations of their support. The classification of generalized symmetries thus reduces to understanding the spectrum of such topological operators across different codimensions. While a generic QFT may admit infinitely many topological operators, their topological nature imposes strong consistency conditions on their structure. In this talk, I will present a set of such constraints in 2+1 and 3+1 dimensions and highlight how they severely restrict the spectrum of topological operators in higher dimensions, in contrast to 1+1 dimensions. Using these constraints, I will argue that the action of non-invertible symmetries on local operators in higher dimensions is highly restricted. In particular, this action is either invertible or, when non-invertible, admits a description in terms of gauging a finite symmetry.
Symmetries of a quantum field theory are implemented by topological operators. These are special extended operators whose correlation functions are insensitive to continuous deformations of their support. The classification of generalized symmetries thus reduces to understanding the spectrum of such topological operators across different codimensions. While a generic QFT may admit infinitely many topological operators, their topological nature imposes strong consistency conditions on their structure. In this talk, I will present a set of such constraints in 2+1 and 3+1 dimensions and highlight how they severely restrict the spectrum of topological operators in higher dimensions, in contrast to 1+1 dimensions. Using these constraints, I will argue that the action of non-invertible symmetries on local operators in higher dimensions is highly restricted. In particular, this action is either invertible or, when non-invertible, admits a description in terms of gauging a finite symmetry.
Posted by: Andrew Svesko
Thu
23 Apr 2026
Scattering amplitude of massless closed strings at genus one
📍 London
Mehregan Doroudiani
(Southampton)
Abstract:
Perturbative calculations of string amplitudes are twofold: an expansion in the string coupling (the genus expansion of the worldsheet) and a low-energy expansion in the momenta. In this talk, I will focus on the low-energy expansion of closed string amplitudes at genus one, specifically for four- and five-point massless states of type IIB superstrings in flat spacetime. Evaluating these amplitudes involves integrating over the moduli space of punctured tori. I will demonstrate how the formalism of equivariant iterated Eisenstein integrals can be used to systematically calculate these integrals. Additionally, I will discuss the implications of these results for the S-duality of type IIB.
Perturbative calculations of string amplitudes are twofold: an expansion in the string coupling (the genus expansion of the worldsheet) and a low-energy expansion in the momenta. In this talk, I will focus on the low-energy expansion of closed string amplitudes at genus one, specifically for four- and five-point massless states of type IIB superstrings in flat spacetime. Evaluating these amplitudes involves integrating over the moduli space of punctured tori. I will demonstrate how the formalism of equivariant iterated Eisenstein integrals can be used to systematically calculate these integrals. Additionally, I will discuss the implications of these results for the S-duality of type IIB.
Posted by: Kymani Armstrong-Williams
Thu
23 Apr 2026
Discovery of unstable singularities
📍 London
Javier Gómez Serrano
(Brown University)
Abstract:
AI for Mathematical Sciences (AIMS) seminar series
In this talk, I will explain how to construct numerically several new unstable singularities to certain equations in fluids (CCF, IPM, Boussinesq) using machine learning methods. Our approach combines curated machine learning architectures and training schemes with a high-precision Gauss-Newton optimizer, achieving accuracies that significantly surpass previous work across all discovered solutions, reaching near double-float machine precision, attaining a level of accuracy constrained only by the round-off errors of the GPU hardware, potentially leading to rigorous mathematical validation via computer-assisted proofs.
To subscribe for the AIMS series please fill out the form https://applications.lims.ac.uk/subscribe-to-aims
AI for Mathematical Sciences (AIMS) seminar series
In this talk, I will explain how to construct numerically several new unstable singularities to certain equations in fluids (CCF, IPM, Boussinesq) using machine learning methods. Our approach combines curated machine learning architectures and training schemes with a high-precision Gauss-Newton optimizer, achieving accuracies that significantly surpass previous work across all discovered solutions, reaching near double-float machine precision, attaining a level of accuracy constrained only by the round-off errors of the GPU hardware, potentially leading to rigorous mathematical validation via computer-assisted proofs.
To subscribe for the AIMS series please fill out the form https://applications.lims.ac.uk/subscribe-to-aims
Posted by: Evgeny Sobko
Wed
22 Apr 2026
Is there a 2d analogue of the 3d Ising CFT?
📍 London
Antonio Antunes
(Laboratoire de Physique del Ecole Normale Superieure (LPENS))
Abstract:
Our understanding of interacting CFTs in d>2 dimensions was revolutionized by modern developments in the analytical and numerical conformal bootstrap. The poster child of this program, the non-exactly solvable 3d Ising CFT, is now understood to an unprecedented level of detail. In contrast, our understanding of 2d CFTs encompasses large classes of exactly solvable models (the so-called rational CFTs), and a set of universal bootstrap results which apply only to "generic" non-exactly solvable CFTs of which no concrete example is available. In this talk, we summarize our recent attempts at constructing such theories by coupling exactly solvable CFTs and flowing to IR fixed points. We will discuss perturbative and non-perturbative constructions as well as some dual bounds on the set of conserved currents in the IR.
Our understanding of interacting CFTs in d>2 dimensions was revolutionized by modern developments in the analytical and numerical conformal bootstrap. The poster child of this program, the non-exactly solvable 3d Ising CFT, is now understood to an unprecedented level of detail. In contrast, our understanding of 2d CFTs encompasses large classes of exactly solvable models (the so-called rational CFTs), and a set of universal bootstrap results which apply only to "generic" non-exactly solvable CFTs of which no concrete example is available. In this talk, we summarize our recent attempts at constructing such theories by coupling exactly solvable CFTs and flowing to IR fixed points. We will discuss perturbative and non-perturbative constructions as well as some dual bounds on the set of conserved currents in the IR.
Posted by: Andrew Svesko
Wed
22 Apr 2026
Black Hole Spectroscopy from a Giant Quantum Vortex
📍 London
Ruth Gregory
(KCL)
Abstract:
Black-hole spectroscopy aims to infer physical properties of black holes by detecting the spectrum of quasi-normal modes (QNMs) they emit while settling towards equilibrium. Gravitational analogs aim to explore aspects of black hole systems by building laboratory experiments that share features of the black hole and its perturbations. A particularly interesting aspect of QNMs is the phenomenon of spectral instability: the complex frequencies of the modes wander as perturbations of the spacetime around the black hole are introduced. Having the ability to simulate in a controlled environment the behaviour of these modes is therefore appealing. I will describe the quantum vortex analog recently developed in the Nottingham Black Hole Laboratory and discuss the problem of how to identify the quasi-normal modes for such a confined system, as well as showing data from the experiment.
Black-hole spectroscopy aims to infer physical properties of black holes by detecting the spectrum of quasi-normal modes (QNMs) they emit while settling towards equilibrium. Gravitational analogs aim to explore aspects of black hole systems by building laboratory experiments that share features of the black hole and its perturbations. A particularly interesting aspect of QNMs is the phenomenon of spectral instability: the complex frequencies of the modes wander as perturbations of the spacetime around the black hole are introduced. Having the ability to simulate in a controlled environment the behaviour of these modes is therefore appealing. I will describe the quantum vortex analog recently developed in the Nottingham Black Hole Laboratory and discuss the problem of how to identify the quasi-normal modes for such a confined system, as well as showing data from the experiment.
Posted by: Gabriele Travaglini
Tue
21 Apr 2026
Fifty years of large-N QCD
📍 London
Marco Bochicchio
(INFN Rome)
Abstract:
We review large-N QCD from its inception to the most recent developments, organizing the subject into four ages.
— Prehistorical: From dual models and string theory to the discovery of deep inelastic scattering and the subsequent rise of QCD.
— Historical: The introduction of the large-N expansion for QCD by ’t Hooft.
— Modern: The “resurrection” of the string program through the emergence of gauge/gravity duality.
— Contemporary: The obstructions to the string program arising from QCD asymptotic freedom and the most recent advancements.
We review large-N QCD from its inception to the most recent developments, organizing the subject into four ages.
— Prehistorical: From dual models and string theory to the discovery of deep inelastic scattering and the subsequent rise of QCD.
— Historical: The introduction of the large-N expansion for QCD by ’t Hooft.
— Modern: The “resurrection” of the string program through the emergence of gauge/gravity duality.
— Contemporary: The obstructions to the string program arising from QCD asymptotic freedom and the most recent advancements.
Posted by: João Vilas Boas
Thu
16 Apr 2026
Weak Hopf monad symmetries of anyon models
📍 London
Zhenghan Wang
(UCSB)
Abstract:
Part of QMUL-LIMS Quantum London Seminar series
Finite group symmetries of anyon models and their gauging are well-understood. It is natural to wonder what are the most general symmetries of anyon models beyond groups. I will argue that it should be weak Hopf monad generalizing weak Hopf algebras and categorical weak Hopf algebras. This is work in progress with many others, so the talk will be informal and guided by the audience.
Part of QMUL-LIMS Quantum London Seminar series
Finite group symmetries of anyon models and their gauging are well-understood. It is natural to wonder what are the most general symmetries of anyon models beyond groups. I will argue that it should be weak Hopf monad generalizing weak Hopf algebras and categorical weak Hopf algebras. This is work in progress with many others, so the talk will be informal and guided by the audience.
Posted by: Matthew Buican
Wed
15 Apr 2026
(A)dS Double Copy in Twistor Space
📍 East of England
Mariana Carrillo-González
(Imperial College London)
Abstract:
The double copy, which relates gravity to the square of Yang–Mills theory, is usually studied in flat spacetime and is known to hold both for scattering amplitudes and for classical field configurations. In this talk, I will present a new approach to extending these results to maximally symmetric curved spacetimes. The new relations are formulated in twistor space, a complex projective space that encodes solutions to the equations of motion as holomorphic data. First, I will discuss the case of AdS₃, where a double copy structure for bulk to boundary correlators and black hole solutions naturally arises in minitwistor space. Then, I will show how in (A)dS₄ one can construct bulk correlation functions using only twistors, dual twistors, and the infinity twistor as building blocks. The relation to coordinate space arises via nested Penrose transform. The boundary limit of these correlators yields CFT correlators that satisfy the expected Ward identities and obey a simple double copy relation.
The double copy, which relates gravity to the square of Yang–Mills theory, is usually studied in flat spacetime and is known to hold both for scattering amplitudes and for classical field configurations. In this talk, I will present a new approach to extending these results to maximally symmetric curved spacetimes. The new relations are formulated in twistor space, a complex projective space that encodes solutions to the equations of motion as holomorphic data. First, I will discuss the case of AdS₃, where a double copy structure for bulk to boundary correlators and black hole solutions naturally arises in minitwistor space. Then, I will show how in (A)dS₄ one can construct bulk correlation functions using only twistors, dual twistors, and the infinity twistor as building blocks. The relation to coordinate space arises via nested Penrose transform. The boundary limit of these correlators yields CFT correlators that satisfy the expected Ward identities and obey a simple double copy relation.
Posted by: Julian Kupka
Wed
15 Apr 2026
Conformal field theories in dimensions two and three
📍 London
Zhenghan Wang
(UCSB)
Abstract:
Conformal field theories are both experimentally relevant and mathematically rigorous. One mathematical approach is via generalized spin chains–-anyonic chains in two spacetime dimensions, and fuzzy sphere models in three spacetime dimensions. The anoyon chain approach in two dimensions has applications to the bulk-edge correspondence of 3d TQFTs and 2d CFTs, and the quantum extended Church-Turing thesis, where Temperley-Lieb and Virasoro algebras are crucial. Fuzzy sphere models conjecturally realize 3d CFTs, and there appears an intriguing fuzzy sphere algebra generated by electron density operators on the two-sphere. I will explain a program based on fuzzy sphere algebra and representation theory to find analogues of the Temperley-Lieb and Virasoro algebras from the fuzzy sphere algebra and the diffeomorphism group of S^1 xS^2 aiming at a generalization to one dimension higher of the 3d TQFT—2d CFT correspondence. This talk is based on joint works with M. Shokrian Zini (arXiv:1706.08497), L. Eck (arXiv:2602.15025), and B. Janssens (arXiv:2603.06876).
Conformal field theories are both experimentally relevant and mathematically rigorous. One mathematical approach is via generalized spin chains–-anyonic chains in two spacetime dimensions, and fuzzy sphere models in three spacetime dimensions. The anoyon chain approach in two dimensions has applications to the bulk-edge correspondence of 3d TQFTs and 2d CFTs, and the quantum extended Church-Turing thesis, where Temperley-Lieb and Virasoro algebras are crucial. Fuzzy sphere models conjecturally realize 3d CFTs, and there appears an intriguing fuzzy sphere algebra generated by electron density operators on the two-sphere. I will explain a program based on fuzzy sphere algebra and representation theory to find analogues of the Temperley-Lieb and Virasoro algebras from the fuzzy sphere algebra and the diffeomorphism group of S^1 xS^2 aiming at a generalization to one dimension higher of the 3d TQFT—2d CFT correspondence. This talk is based on joint works with M. Shokrian Zini (arXiv:1706.08497), L. Eck (arXiv:2602.15025), and B. Janssens (arXiv:2603.06876).
Posted by: David Vegh
Wed
15 Apr 2026
Automorphic forms, L-functions, and the conformal bootstrap
📍 London
Dalimil Mazáč
(IPhT, Saclay)
Abstract:
I will review an analogy between conformal field theory in d dimensions, and spectral theory of automorphic forms on hyperbolic (d+1)-manifolds. Building on this analogy, I will prove a new bound on triple product L-functions, using the conformal bootstrap. I will discuss in which sense the conformal bootstrap axioms may be complete. Finally, I will review a recent remarkable theorem of Adve that establishes such completeness in the context of the above mentioned analogy. Based on works with A. Adve, J. Bonifacio, P. Kravchuk, S. Pal, A. Radcliffe, and G. Rogelberg.
I will review an analogy between conformal field theory in d dimensions, and spectral theory of automorphic forms on hyperbolic (d+1)-manifolds. Building on this analogy, I will prove a new bound on triple product L-functions, using the conformal bootstrap. I will discuss in which sense the conformal bootstrap axioms may be complete. Finally, I will review a recent remarkable theorem of Adve that establishes such completeness in the context of the above mentioned analogy. Based on works with A. Adve, J. Bonifacio, P. Kravchuk, S. Pal, A. Radcliffe, and G. Rogelberg.
Posted by: David Vegh
Thu
9 Apr 2026
Anomalies in Topological Orders: From Algebraic Topology to Physical Realizations
📍 London
Weicheng Ye
(UBC)
Abstract:
Quantum London Seminar (QMUL+LIMS joint seminar).
Talk info can be found on https://lims.ac.uk/
Topological orders are fascinating objects with profound
applications across mathematical physics, condensed matter physics,
and quantum information science. This talk explores the critical
interplay between anomalous symmetry actions of topological orders and
their physical realizations. I will begin by formalizing the
mathematical definition of anomalies in topological orders, framing
them as rigorous lifting obstructions in algebraic topology. Building
on this foundation, I will introduce diagrammatic techniques for
calculating these anomalies explicitly. Finally, I will demonstrate
how these mathematical anomalies dictate whether a given topological
order can be physically realized in lattice systems or quantum field
theories through the framework of anomaly matching.
This talk is based on arXiv: 2210.02444, 2309.15118, 2312.13341, and 2510.24834.
Quantum London Seminar (QMUL+LIMS joint seminar).
Talk info can be found on https://lims.ac.uk/
Topological orders are fascinating objects with profound
applications across mathematical physics, condensed matter physics,
and quantum information science. This talk explores the critical
interplay between anomalous symmetry actions of topological orders and
their physical realizations. I will begin by formalizing the
mathematical definition of anomalies in topological orders, framing
them as rigorous lifting obstructions in algebraic topology. Building
on this foundation, I will introduce diagrammatic techniques for
calculating these anomalies explicitly. Finally, I will demonstrate
how these mathematical anomalies dictate whether a given topological
order can be physically realized in lattice systems or quantum field
theories through the framework of anomaly matching.
This talk is based on arXiv: 2210.02444, 2309.15118, 2312.13341, and 2510.24834.
Posted by: JUVEN WANG
Tue
7 Apr 2026
Insights from the crosscap state toward non-orientable TQFTs
📍 London
Ippo Orii
(IPMU, U Tokyo)
Abstract:
Quantum London Seminar (QMUL+LIMS joint seminar).
Talk info can be found on https://lims.ac.uk/
A topological quantum field theory (TQFT) is a class of field theories that have been successfully formulated in a mathematically rigorous way, providing a framework for describing physical phenomena independent of the spacetime metric. In particular, (2+1)-dimensional TQFTs—exemplified by Chern–Simons theory—have been extensively studied in both high-energy and condensed-matter physics as toy models of low-dimensional quantum gravity and as effective theories describing the fractional quantum Hall effect.
TQFTs with time-reversal symmetry are equivalent to considering such theories on non-orientable manifolds. However, While these systems exhibit rich mathematical structures, many physical aspects remain unresolved, and a complete mathematical formulation is still lacking. Among the most important objects for analyzing time-reversal-symmetric TQFTs is the crosscap state, which captures the essential features of non-orientable TQFTs.
In this talk, I will provide an overview of the current understanding of systems with time-reversal symmetry through the study of crosscap states, incorporating some of my recent results. And I will also present a new idea suggesting that the study of crosscap states may contain key insights toward a rigorous formulation of non-orientable TQFTs.
Quantum London Seminar (QMUL+LIMS joint seminar).
Talk info can be found on https://lims.ac.uk/
A topological quantum field theory (TQFT) is a class of field theories that have been successfully formulated in a mathematically rigorous way, providing a framework for describing physical phenomena independent of the spacetime metric. In particular, (2+1)-dimensional TQFTs—exemplified by Chern–Simons theory—have been extensively studied in both high-energy and condensed-matter physics as toy models of low-dimensional quantum gravity and as effective theories describing the fractional quantum Hall effect.
TQFTs with time-reversal symmetry are equivalent to considering such theories on non-orientable manifolds. However, While these systems exhibit rich mathematical structures, many physical aspects remain unresolved, and a complete mathematical formulation is still lacking. Among the most important objects for analyzing time-reversal-symmetric TQFTs is the crosscap state, which captures the essential features of non-orientable TQFTs.
In this talk, I will provide an overview of the current understanding of systems with time-reversal symmetry through the study of crosscap states, incorporating some of my recent results. And I will also present a new idea suggesting that the study of crosscap states may contain key insights toward a rigorous formulation of non-orientable TQFTs.
Posted by: JUVEN WANG
Tue
7 Apr 2026
Geometric Categories for Continuous Gauging
📍 London
Matthew Yu
(Oxford)
Abstract:
Quantum London Seminar (QMUL+LIMS joint seminar).
Talk info can be found on https://lims.ac.uk/
I will present a unified categorical framework which encodes gauging of continuous and finite symmetries in arbitrary spacetime dimension. I will show how this framework can identify electric and magnetic symmetries expected in G-gauge theory, and how to capture electric symmetry breaking resulting from the addition of charged matter. I introduce geometric categories, i.e. categories internal to stacks. This allows us to extend (de)equivariantization of fusion categories to continuous groups, construct a functorial SymTFT and boundaries for this theory, and compute the relevant categories of endomorphisms and Drinfeld centers.
Quantum London Seminar (QMUL+LIMS joint seminar).
Talk info can be found on https://lims.ac.uk/
I will present a unified categorical framework which encodes gauging of continuous and finite symmetries in arbitrary spacetime dimension. I will show how this framework can identify electric and magnetic symmetries expected in G-gauge theory, and how to capture electric symmetry breaking resulting from the addition of charged matter. I introduce geometric categories, i.e. categories internal to stacks. This allows us to extend (de)equivariantization of fusion categories to continuous groups, construct a functorial SymTFT and boundaries for this theory, and compute the relevant categories of endomorphisms and Drinfeld centers.
Posted by: JUVEN WANG
Thu
2 Apr 2026
Mathematical exploration at scale
📍 London
Adam Zsolt Wagner
(Google DeepMind)
Abstract:
In this second talk in the AI for Mathematical Sciences (AIMS) seminar series Dr Adam Zsolt Wagner explores the frontiers of automated mathematical discovery. With an emphasis on his work at Google DeepMind, he discusses tools such AlphaEvolve that aim to bridge the gap between human intuition and the vast space of potential mathematical constructions. By treating mathematical problems as search tasks within “language space” these tools can generate counterexamples, find novel configurations and significantly reduce the manual effort required to explore ideas and test complex hypotheses.
Dr Wagner demonstrates how these AI-driven approaches are being applied to problems in combinatorics and beyond. He discusses the mechanics of FunSearch and AlphaEvolve, shares insights from collaborative work with Javier Gomez-Serrano and Terence Tao and provides a framework for mathematicians and theoretical physicists to determine which AI search strategies are best suited for their own research.
To subscribe for the AIMS series please fill out the form https://applications.lims.ac.uk/subscribe-to-aims
In this second talk in the AI for Mathematical Sciences (AIMS) seminar series Dr Adam Zsolt Wagner explores the frontiers of automated mathematical discovery. With an emphasis on his work at Google DeepMind, he discusses tools such AlphaEvolve that aim to bridge the gap between human intuition and the vast space of potential mathematical constructions. By treating mathematical problems as search tasks within “language space” these tools can generate counterexamples, find novel configurations and significantly reduce the manual effort required to explore ideas and test complex hypotheses.
Dr Wagner demonstrates how these AI-driven approaches are being applied to problems in combinatorics and beyond. He discusses the mechanics of FunSearch and AlphaEvolve, shares insights from collaborative work with Javier Gomez-Serrano and Terence Tao and provides a framework for mathematicians and theoretical physicists to determine which AI search strategies are best suited for their own research.
To subscribe for the AIMS series please fill out the form https://applications.lims.ac.uk/subscribe-to-aims
Posted by: Evgeny Sobko
Wed
1 Apr 2026
Black hole entropy in higher derivative theories of gravity
📍 London
Sayantani Bhattacharyya
(University of Edinburgh)
Abstract:
Any UV complete theory of gravity typically in its low energy classical limit will generate higher derivative corrections to Einstein's General Theory of Relativity (GTR). GTR admits the black hole solution which satisfies the laws of thermodynamics. Black hole solutions continue to exist classically in presence of perturbative higher derivative corrections. Also, we expect the black hole to satisfy the same thermodynamic laws at least order by order in an expansion in higher derivative couplings. However, we still do not have any completely satisfactory proof or counter example for this expectation. In this talk we shall discuss how we have approached this problem in a classical setting and the current status of our understanding.
Any UV complete theory of gravity typically in its low energy classical limit will generate higher derivative corrections to Einstein's General Theory of Relativity (GTR). GTR admits the black hole solution which satisfies the laws of thermodynamics. Black hole solutions continue to exist classically in presence of perturbative higher derivative corrections. Also, we expect the black hole to satisfy the same thermodynamic laws at least order by order in an expansion in higher derivative couplings. However, we still do not have any completely satisfactory proof or counter example for this expectation. In this talk we shall discuss how we have approached this problem in a classical setting and the current status of our understanding.
Posted by: Andrew Svesko
March 2026
Tue
31 Mar 2026
Black hole states in quantum spin chains
📍 London
Konstantin Zarembo
(NORDITA)
Abstract:
Holography maps a thermal ensemble of a QFT to a black hole. Infall inside the black hole enables 1pt functions for local operators. In the spin-chain description of 1pt functions, the black hole maps to a boundary state with quite unusual features that I will describe. The state breaks integrability, has a logarithmic entanglement entropy and thermalizes at infinite temperature. This can be confronted with 1pt function arising from D-branes, which preserve integrability and in some cases can be computed exactly by Bethe Ansatz.
Holography maps a thermal ensemble of a QFT to a black hole. Infall inside the black hole enables 1pt functions for local operators. In the spin-chain description of 1pt functions, the black hole maps to a boundary state with quite unusual features that I will describe. The state breaks integrability, has a logarithmic entanglement entropy and thermalizes at infinite temperature. This can be confronted with 1pt function arising from D-branes, which preserve integrability and in some cases can be computed exactly by Bethe Ansatz.
Posted by: Evgeny Sobko
Tue
31 Mar 2026
Bootstrapping thermal CFTs
📍 London
Julien Barrat
(DESY)
Abstract:
Thermal conformal field theories (CFTs) describe quantum systems at finite temperature, with applications ranging from laboratory systems to the holographic description of black holes. Although the thermal background breaks global conformal symmetry, key local data of the zero-temperature theory—such as the spectrum and operator product expansion—remain intact. Thermal correlators are further constrained by the Kubo–Martin–Schwinger (KMS) condition, which enforces periodicity along the thermal circle and plays a role analogous to crossing symmetry in zero-temperature systems. Placing the theory at finite volume enriches this structure and, in holographic settings, allows for the emergence of distinct phases.
In this talk, I will present analytic and numerical bootstrap approaches to solving the KMS condition for thermal two-point functions. These methods reconstruct correlators from minimal input and apply across weakly and strongly coupled regimes. I will illustrate them in free theories, O(N) models, and holographic CFTs, and conclude with a brief outlook on ongoing developments.
Thermal conformal field theories (CFTs) describe quantum systems at finite temperature, with applications ranging from laboratory systems to the holographic description of black holes. Although the thermal background breaks global conformal symmetry, key local data of the zero-temperature theory—such as the spectrum and operator product expansion—remain intact. Thermal correlators are further constrained by the Kubo–Martin–Schwinger (KMS) condition, which enforces periodicity along the thermal circle and plays a role analogous to crossing symmetry in zero-temperature systems. Placing the theory at finite volume enriches this structure and, in holographic settings, allows for the emergence of distinct phases.
In this talk, I will present analytic and numerical bootstrap approaches to solving the KMS condition for thermal two-point functions. These methods reconstruct correlators from minimal input and apply across weakly and strongly coupled regimes. I will illustrate them in free theories, O(N) models, and holographic CFTs, and conclude with a brief outlook on ongoing developments.
Posted by: João Vilas Boas
Thu
26 Mar 2026
Scattering amplitude of massless closed strings at genus one
📍 London
Mehregan Doroudiani
(Southampton)
Abstract:
Perturbative calculations of string amplitudes are twofold: an expansion in the string coupling (the genus expansion of the worldsheet) and a low-energy expansion in the momenta. In this talk, I will focus on the low-energy expansion of closed string amplitudes at genus one, specifically for four- and five-point massless states of type IIB superstrings in flat spacetime. Evaluating these amplitudes involves integrating over the moduli space of punctured tori. I will demonstrate how the formalism of equivariant iterated Eisenstein integrals can be used to systematically calculate these integrals. Additionally, I will discuss the implications of these results for the S-duality of type IIB.
Perturbative calculations of string amplitudes are twofold: an expansion in the string coupling (the genus expansion of the worldsheet) and a low-energy expansion in the momenta. In this talk, I will focus on the low-energy expansion of closed string amplitudes at genus one, specifically for four- and five-point massless states of type IIB superstrings in flat spacetime. Evaluating these amplitudes involves integrating over the moduli space of punctured tori. I will demonstrate how the formalism of equivariant iterated Eisenstein integrals can be used to systematically calculate these integrals. Additionally, I will discuss the implications of these results for the S-duality of type IIB.
Posted by: Nathan Moynihan
Wed
25 Mar 2026
Aspects of the ODE/IM Correspondence
📍 London
Roberto Tateo
(INFN, Turin)
Abstract:
The ODE/IM correspondence is a striking bridge between spectral theory and exact methods in integrable quantum field theory. In this talk, I will present some aspects of this correspondence from the point of view of integrable models, with particular emphasis on functional relations such as Y-systems and on their role in the thermodynamic Bethe ansatz. I will then discuss several extensions motivated by deformations of simple theories, including richer coupled structures and twisted sectors. The goal is to illustrate both the general framework and some more recent directions that may lead to broader versions of ODE/IM.
The ODE/IM correspondence is a striking bridge between spectral theory and exact methods in integrable quantum field theory. In this talk, I will present some aspects of this correspondence from the point of view of integrable models, with particular emphasis on functional relations such as Y-systems and on their role in the thermodynamic Bethe ansatz. I will then discuss several extensions motivated by deformations of simple theories, including richer coupled structures and twisted sectors. The goal is to illustrate both the general framework and some more recent directions that may lead to broader versions of ODE/IM.
Posted by: Andrew Svesko
Mon
23 Mar 2026
Lonti: classical and quantum energy conditions (4/4)
📍 London
Eleni Kontou
Abstract:
Energy conditions were originally formulated as pointwise bounds on contractions of the stress–energy tensor and have played a central role as assumptions in many foundational results of classical general relativity, most notably the singularity theorems. However, these conditions are generically violated by quantum fields, which admit states with locally negative energy density. Such violations are nevertheless constrained: quantum energy inequalities impose bounds on the magnitude and duration of negative energy.
In this course, I will first introduce the classical energy conditions and review their physical motivation and known violations. Then I will provide a brief introduction to quantum field theory on curved spacetimes and demonstrate how quantum energy inequalities can be derived. Finally, I will discuss in detail the average null energy condition and the limitations it imposes to causality violating spacetimes.
Course plan:
Lecture 1: Classical energy conditions and their violations
Lecture 2: Quantum field theory on curved spacetimes
Lecture 3: A derivation of a quantum energy inequality
Lecture 4: The average null energy condition
Energy conditions were originally formulated as pointwise bounds on contractions of the stress–energy tensor and have played a central role as assumptions in many foundational results of classical general relativity, most notably the singularity theorems. However, these conditions are generically violated by quantum fields, which admit states with locally negative energy density. Such violations are nevertheless constrained: quantum energy inequalities impose bounds on the magnitude and duration of negative energy.
In this course, I will first introduce the classical energy conditions and review their physical motivation and known violations. Then I will provide a brief introduction to quantum field theory on curved spacetimes and demonstrate how quantum energy inequalities can be derived. Finally, I will discuss in detail the average null energy condition and the limitations it imposes to causality violating spacetimes.
Course plan:
Lecture 1: Classical energy conditions and their violations
Lecture 2: Quantum field theory on curved spacetimes
Lecture 3: A derivation of a quantum energy inequality
Lecture 4: The average null energy condition
Posted by: Damian Galante
Thu
19 Mar 2026
2->N scattering in QCD and gravity: from amplitudes to shockwaves
📍 London
Raju Venugopalan
(Stony Brook University)
Abstract:
The dynamics of QCD, unlike QED and gravity, is predominantly quantum in nature. We outline how a semi-classical regime emerges in the high energy Regge limit of the theory, where the dynamics is described by Yang-Mills equations, and multi-particle production is described by shockwave scattering. We demonstrate that trans-Planckian scattering in Einstein gravity can be understood similarly, with emergent double copy structures in gravitational radiation. We discuss possible consequences of this IR <-> UV correspondence in the two theories.
The dynamics of QCD, unlike QED and gravity, is predominantly quantum in nature. We outline how a semi-classical regime emerges in the high energy Regge limit of the theory, where the dynamics is described by Yang-Mills equations, and multi-particle production is described by shockwave scattering. We demonstrate that trans-Planckian scattering in Einstein gravity can be understood similarly, with emergent double copy structures in gravitational radiation. We discuss possible consequences of this IR <-> UV correspondence in the two theories.
Posted by: Riccardo Gonzo
Thu
19 Mar 2026
Gravitational charges and radiation in de Sitter
📍 London
Kostas Skenderis
(Southampton)
Abstract:
I will present a first principles rigorous derivation of gravitational charges in de Sitter using (suitably adapted version of) Noether’s theorem, and show that they satisfy a flux-balance law. The variational problem in de Sitter gravity requires that one specifies a conformal class up to diffeomorpshisms at future and past infinity. Gravitational radiation is possible only when the conformal class is non-trivial. I will illustrate the discussion with several exact solutions, including the radiative Robinson-Trautman-dS solution, which I will use to demonstrate the existence of conserved charges even in the absence of asymptotic (conformal) Killing vectors, and also the existence of monotonic charges, charges that are not conserved but rather change monotonically under time evolution. An example of a monotonic change is the Bondi mass.
I will present a first principles rigorous derivation of gravitational charges in de Sitter using (suitably adapted version of) Noether’s theorem, and show that they satisfy a flux-balance law. The variational problem in de Sitter gravity requires that one specifies a conformal class up to diffeomorpshisms at future and past infinity. Gravitational radiation is possible only when the conformal class is non-trivial. I will illustrate the discussion with several exact solutions, including the radiative Robinson-Trautman-dS solution, which I will use to demonstrate the existence of conserved charges even in the absence of asymptotic (conformal) Killing vectors, and also the existence of monotonic charges, charges that are not conserved but rather change monotonically under time evolution. An example of a monotonic change is the Bondi mass.
Posted by: Nathan Moynihan
Wed
18 Mar 2026
Consequences of symmetry breaking on conformal defect data
📍 London
Philine Van Vliet
(ENS)
Abstract:
Conformal defects break part of the symmetry of a bulk CFT. The broken Ward identities lead to very general sum rules on the defect CFT data as well as on the data of bulk operators in the presence of a defect. We call these sum rules "defect soft theorems", and they hold generally for defects which break conformal symmetry, flavor symmetry, or supersymmetry. In this talk I will focus on line defects for which we can rewrite the constraints in dispersive sum rule form, and show how the defect soft theorems impose constraints on the defect spectrum and OPE coefficients.
This talk is based on https://arxiv.org/pdf/2509.26561 with B. Girault and M. Paulos, and on work in progress with G. Bliard, J. Julius, M. Paulos and N. Suchel.
Conformal defects break part of the symmetry of a bulk CFT. The broken Ward identities lead to very general sum rules on the defect CFT data as well as on the data of bulk operators in the presence of a defect. We call these sum rules "defect soft theorems", and they hold generally for defects which break conformal symmetry, flavor symmetry, or supersymmetry. In this talk I will focus on line defects for which we can rewrite the constraints in dispersive sum rule form, and show how the defect soft theorems impose constraints on the defect spectrum and OPE coefficients.
This talk is based on https://arxiv.org/pdf/2509.26561 with B. Girault and M. Paulos, and on work in progress with G. Bliard, J. Julius, M. Paulos and N. Suchel.
Posted by: Jesse van Muiden
Wed
18 Mar 2026
2-> N scattering in QCD and gravity: from amplitudes to shockwaves
📍 London
Raju Venugopalan
(Stony Brook University)
Abstract:
The dynamics of QCD, unlike QED and gravity, is predominantly quantum in nature. We outline how a semi-classical regime emerges in the high energy Regge limit of the theory, where the dynamics is described by Yang-Mills equations, and multi-particle production is described by shockwave scattering. We demonstrate that trans-Planckian scattering in Einstein gravity can be understood similarly, with emergent double copy structures in gravitational radiation. We discuss possible consequences of this IR <-> UV correspondence in the two theories.
The dynamics of QCD, unlike QED and gravity, is predominantly quantum in nature. We outline how a semi-classical regime emerges in the high energy Regge limit of the theory, where the dynamics is described by Yang-Mills equations, and multi-particle production is described by shockwave scattering. We demonstrate that trans-Planckian scattering in Einstein gravity can be understood similarly, with emergent double copy structures in gravitational radiation. We discuss possible consequences of this IR <-> UV correspondence in the two theories.
Posted by: Andrew Svesko
Wed
18 Mar 2026
Bootstrapping ABJM theories through Tracy-Widom formalisms
📍 London
Alessandro Testa
(IPHT)
Abstract:
In this talk, we will present a unified Fermi-gas framework for computing BPS observables in ABJM theory on S^3. Supersymmetric localization reduces the problem to an interacting matrix model that can be interpreted as a one-dimensional ideal Fermi gas, whose dynamics is encoded in a set of TBA-like equations. We will show that these equations enable a non-perturbative bootstrap approach that systematically captures the instanton sectors of the free energy and winding Wilson loops. As applications, we will provide an analytic proofs of several previously conjectural formulas and derive closed-form expressions, valid at arbitrary winding number, for the leading membrane- and worldsheet-instanton corrections to the 1/6- and 1/2-BPS Wilson loops.
In this talk, we will present a unified Fermi-gas framework for computing BPS observables in ABJM theory on S^3. Supersymmetric localization reduces the problem to an interacting matrix model that can be interpreted as a one-dimensional ideal Fermi gas, whose dynamics is encoded in a set of TBA-like equations. We will show that these equations enable a non-perturbative bootstrap approach that systematically captures the instanton sectors of the free energy and winding Wilson loops. As applications, we will provide an analytic proofs of several previously conjectural formulas and derive closed-form expressions, valid at arbitrary winding number, for the leading membrane- and worldsheet-instanton corrections to the 1/6- and 1/2-BPS Wilson loops.
Posted by: Jesse van Muiden
Tue
17 Mar 2026
Creating the Matter Antimatter Asymmetry of the Universe out of Higgs Bubble Collisions
📍 London
Geraldine Servant
(DESY)
Abstract:
Explaining the matter antimatter asymmetry of the universe requires a source of baryon number violation.
Baryon number is efficiently violated in the Standard Model of particle physics at high temperature through electroweak vacuum transitions, the so-called sphaleron processes, which play a key role in essentially all models of baryogenesis, whether at the electroweak scale or well beyond, as in leptogenesis.
I will show that these transitions can also be induced at zero temperature for large departure from equilibrium of the Higgs field.
In particular, we compute the rate of baryon number violation at T=0 arising from Higgs bubble collisions during a strong first-order electroweak phase transition. This opens up the possibility for a new mechanism of electroweak baryogenesis in the supercooled limit.
Explaining the matter antimatter asymmetry of the universe requires a source of baryon number violation.
Baryon number is efficiently violated in the Standard Model of particle physics at high temperature through electroweak vacuum transitions, the so-called sphaleron processes, which play a key role in essentially all models of baryogenesis, whether at the electroweak scale or well beyond, as in leptogenesis.
I will show that these transitions can also be induced at zero temperature for large departure from equilibrium of the Higgs field.
In particular, we compute the rate of baryon number violation at T=0 arising from Higgs bubble collisions during a strong first-order electroweak phase transition. This opens up the possibility for a new mechanism of electroweak baryogenesis in the supercooled limit.
Posted by: Sebastian Cespedes
Thu
12 Mar 2026
Quasinormal perspective on nonthermal fixed points
📍 London
Michal P. Heller
(Ghent University / Jagiellonian University)
Abstract:
I will present nonthermal fixed points as paradigmatic far from equilibrium weak coupling phenomena characterised by a self-similar evolution in time. I will then discuss what strong coupling perspective based on the quasinormal modes insights into holographic thermalization and hydrodynamics can teach us about nonthermal fixed points. Based on 2307.07545, 2502.01622 and 2504.18754.
I will present nonthermal fixed points as paradigmatic far from equilibrium weak coupling phenomena characterised by a self-similar evolution in time. I will then discuss what strong coupling perspective based on the quasinormal modes insights into holographic thermalization and hydrodynamics can teach us about nonthermal fixed points. Based on 2307.07545, 2502.01622 and 2504.18754.
Posted by: João Vilas Boas
Thu
12 Mar 2026
The Bootstrap Program for the Strong Force
📍 London
Leonardo Rastelli
(C.N. Yang Institute for Theoretical Physics, Stony Brook University)
Abstract:
In the 1960s, the dominant approach to the strong interaction was the S-matrix bootstrap: the idea that the hadronic spectrum and scattering amplitudes could be determined from the general principles of causality and unitarity. This program culminated in the Veneziano amplitude which gave birth to string theory, but was abandoned as an approach to the strong force after the identification of Quantum Chromodynamics (QCD) as the microscopic theory of hadron physics. Yet QCD at low energies remains largely unsolved. Professor Rastelli will describe how modern bootstrap methods, powered new theoretical insights and computational techniques, allow us to revisit this classic program with unprecedented rigor.
In the 1960s, the dominant approach to the strong interaction was the S-matrix bootstrap: the idea that the hadronic spectrum and scattering amplitudes could be determined from the general principles of causality and unitarity. This program culminated in the Veneziano amplitude which gave birth to string theory, but was abandoned as an approach to the strong force after the identification of Quantum Chromodynamics (QCD) as the microscopic theory of hadron physics. Yet QCD at low energies remains largely unsolved. Professor Rastelli will describe how modern bootstrap methods, powered new theoretical insights and computational techniques, allow us to revisit this classic program with unprecedented rigor.
Posted by: Jesse van Muiden
Wed
11 Mar 2026
A Holographic Constraint on Scale Separation
📍 East of England
Filippo Revello
(KU Leuven)
Abstract:
The problem of scale separation - i.e. whether String Theory admits AdS vacua where the size of the extra dimensions can be made parametrically smaller than the AdS radius - is an outstanding problem in string phenomenology. Moreover, it is also a fundamental question in Holography and Conformal Field Theory. After a pedagogical introduction covering the connections between these aspects, I will present a new consistency condition for the compatibility of a gravitational effective field theory in AdS with a dual holographic description. The condition amounts to the requirement that certain (properly defined) cubic interactions in the bulk must vanish. Remarkably, the constraint is satisfied for the well-known, scale-separated DGKT vacua in type IIA, thanks to a series of non-trivial cancellations. I will conclude with a possible bulk interpretation, as well as a future outlook.
The problem of scale separation - i.e. whether String Theory admits AdS vacua where the size of the extra dimensions can be made parametrically smaller than the AdS radius - is an outstanding problem in string phenomenology. Moreover, it is also a fundamental question in Holography and Conformal Field Theory. After a pedagogical introduction covering the connections between these aspects, I will present a new consistency condition for the compatibility of a gravitational effective field theory in AdS with a dual holographic description. The condition amounts to the requirement that certain (properly defined) cubic interactions in the bulk must vanish. Remarkably, the constraint is satisfied for the well-known, scale-separated DGKT vacua in type IIA, thanks to a series of non-trivial cancellations. I will conclude with a possible bulk interpretation, as well as a future outlook.
Posted by: Julian Kupka
Wed
11 Mar 2026
Asymptotic symmetries of gravity: the Hamiltonian point of view
📍 London
Marc Henneaux
(Collège de France)
Abstract:
******* Please register at: https://forms.gle/9fF2GWkoMWv4D2J19 *******
Asymptotic symmetries, sometimes also known as "large gauge transformations", provide important dynamical information on theories with a gauge freedom formulated on spacetimes having a "boundary at infinity". A review of asymptotic symmetries will be given following the Hamiltonian approach. General features (such as the form of the symmetry generators and the structure of the algebra) will be explained. The discussion will focus on gravity in the asymptotically flat context, where the relevant asymptotic symmetry algebra is the infinite-dimensional BMS algebra.
******* Please register at: https://forms.gle/9fF2GWkoMWv4D2J19 *******
Asymptotic symmetries, sometimes also known as "large gauge transformations", provide important dynamical information on theories with a gauge freedom formulated on spacetimes having a "boundary at infinity". A review of asymptotic symmetries will be given following the Hamiltonian approach. General features (such as the form of the symmetry generators and the structure of the algebra) will be explained. The discussion will focus on gravity in the asymptotically flat context, where the relevant asymptotic symmetry algebra is the infinite-dimensional BMS algebra.
Posted by: Damian Galante
Wed
11 Mar 2026
Scalar potentials and their vacua in string theory
📍 London
Timm Wrase
(Lehigh University)
Abstract:
******* Please register at: https://forms.gle/9fF2GWkoMWv4D2J19 *******
A central challenge in string phenomenology is to understand the scalar potentials that arise from compactifications to lower-dimensional effective field theories. In recent years, the swampland program has called into question many earlier proposals for semi-realistic vacua in the string landscape. In this talk, I will review the relevant swampland conjectures and discuss the current status of proposed counterexamples. I will begin with the construction of four-dimensional N=1 Minkowski vacua with no massless scalar fields. I will then present recently discovered low-energy effective theories with negative cosmological constants - namely AdS vacua - arising in Type II and heterotic string compactifications on G2 spaces.
******* Please register at: https://forms.gle/9fF2GWkoMWv4D2J19 *******
A central challenge in string phenomenology is to understand the scalar potentials that arise from compactifications to lower-dimensional effective field theories. In recent years, the swampland program has called into question many earlier proposals for semi-realistic vacua in the string landscape. In this talk, I will review the relevant swampland conjectures and discuss the current status of proposed counterexamples. I will begin with the construction of four-dimensional N=1 Minkowski vacua with no massless scalar fields. I will then present recently discovered low-energy effective theories with negative cosmological constants - namely AdS vacua - arising in Type II and heterotic string compactifications on G2 spaces.
Posted by: Damian Galante
Tue
10 Mar 2026
A “dictionary” to test GR with GW: from observations to theory
📍 London
Suvendu Giri
(Uppsala University)
Abstract:
GR, while one of the most successful and well-tested theories to date, is expected to receive corrections at high energies—through higher-curvature terms, additional degrees of freedom, or both. Given the vast landscape of possible extensions, how can we test them in a systematic way?
I will present a general framework for interpreting deviations in gravitational wave data, focusing on the inspiral regime probed by LIGO. The key idea is that genuine beyond-GR effects exhibit characteristic mass scalings, determined by the curvature order and field content of the underlying theory. Using techniques from Post-Newtonian Effective Field Theory (PN-EFT), we construct a dictionary between such corrections and their imprint on the waveform. This allows broad classes of higher-curvature modifications to be identified or constrained directly from data, without relying on specific models. The talk will be based on arXiv:2507.17143.
GR, while one of the most successful and well-tested theories to date, is expected to receive corrections at high energies—through higher-curvature terms, additional degrees of freedom, or both. Given the vast landscape of possible extensions, how can we test them in a systematic way?
I will present a general framework for interpreting deviations in gravitational wave data, focusing on the inspiral regime probed by LIGO. The key idea is that genuine beyond-GR effects exhibit characteristic mass scalings, determined by the curvature order and field content of the underlying theory. Using techniques from Post-Newtonian Effective Field Theory (PN-EFT), we construct a dictionary between such corrections and their imprint on the waveform. This allows broad classes of higher-curvature modifications to be identified or constrained directly from data, without relying on specific models. The talk will be based on arXiv:2507.17143.
Posted by: João Vilas Boas
Mon
9 Mar 2026
AI and the formalization of mathematics
📍 London
Kevin Buzzard
(Imperial)
Abstract:
Formalization of mathematics in computer theorem provers such as Lean is an area which has seen a huge growth in popularity in this decade. AI tools which can write Lean code are now appearing, and people are using these tools to verify LLM output. I'll talk about motivations for the formalization of mathematics, bottlenecks, and the role which AI has to play in the future of this area.
This is the first lecture in the new AI for Mathematical Sciences (AIMS) seminar series: https://lims.ac.uk/events/aims/
To subscribe, please fill in the form: https://applications.lims.ac.uk/subscribe-to-aims
Formalization of mathematics in computer theorem provers such as Lean is an area which has seen a huge growth in popularity in this decade. AI tools which can write Lean code are now appearing, and people are using these tools to verify LLM output. I'll talk about motivations for the formalization of mathematics, bottlenecks, and the role which AI has to play in the future of this area.
This is the first lecture in the new AI for Mathematical Sciences (AIMS) seminar series: https://lims.ac.uk/events/aims/
To subscribe, please fill in the form: https://applications.lims.ac.uk/subscribe-to-aims
Posted by: Evgeny Sobko
Thu
5 Mar 2026
Color-kinematics duality from an algebra of superforms
📍 London
Olaf Hohm
(Humboldt)
Abstract:
I give an introduction to an ongoing research program to find a first-principle and off-shell derivation of color-kinematics duality and the double-copy nature of gravity directly from field theory,
using the framework of homotopy algebra. I focus on recent progress that maps the homotopy algebra of (color-stripped) Yang-Mills theory to the (de Rham) algebra of differential forms on a simple superspace.
I give an introduction to an ongoing research program to find a first-principle and off-shell derivation of color-kinematics duality and the double-copy nature of gravity directly from field theory,
using the framework of homotopy algebra. I focus on recent progress that maps the homotopy algebra of (color-stripped) Yang-Mills theory to the (de Rham) algebra of differential forms on a simple superspace.
Posted by: Nathan Moynihan
Wed
4 Mar 2026
Post-Newtonian theory and radiation reaction
📍 London
David Trestini
(University of Southampton)
Abstract:
After reviewing the main aspects of post-Newtonian theory and the current state of the art, I will discuss recent advances with regards to radiation reaction. In particular, I will discuss the difference between conservative and binding energy at fourth post-Newtonian order and its impact on waveform modeling.
After reviewing the main aspects of post-Newtonian theory and the current state of the art, I will discuss recent advances with regards to radiation reaction. In particular, I will discuss the difference between conservative and binding energy at fourth post-Newtonian order and its impact on waveform modeling.
Posted by: Riccardo Gonzo
Wed
4 Mar 2026
A String Theory for 2D Yang-Mills
📍 London
Suman Kundu
(SISSA)
Abstract:
Two-dimensional gauge theories with charged matter fields are useful toy models for studying gauge theory dynamics, particularly for examining the duality of large N gauge theories to perturbative string theories. A useful starting point for such studies is pure Yang-Mills theory, which is exactly solvable. Its 1/N expansion was interpreted as a string theory by Gross and Taylor, but they did not provide a world sheet action for this string theory, and such an action is useful for coupling it to matter fields. The chiral sector of the Yang-Mills theory can be written as a sum over holomorphic maps and has useful world sheet descriptions, but the full theory includes more general extremal-area maps; a formal world sheet action including all these maps in a “topological rigid string theory” was written by Hořava many years ago, but various subtleties arise when trying to use it for computations. In this talk, we will construct a Polyakov-like generalization of Hořava’s world sheet action that is well-defined, and we will show how it reproduces the free limit of the Yang-Mills theory, both by formal arguments and by explicitly computing its partition function in several cases. We will also discuss the generalization of this string theory with boundaries, corresponding to Wilson loops, and mention possible ways to generalize it for the finite-coupling gauge theory.
Two-dimensional gauge theories with charged matter fields are useful toy models for studying gauge theory dynamics, particularly for examining the duality of large N gauge theories to perturbative string theories. A useful starting point for such studies is pure Yang-Mills theory, which is exactly solvable. Its 1/N expansion was interpreted as a string theory by Gross and Taylor, but they did not provide a world sheet action for this string theory, and such an action is useful for coupling it to matter fields. The chiral sector of the Yang-Mills theory can be written as a sum over holomorphic maps and has useful world sheet descriptions, but the full theory includes more general extremal-area maps; a formal world sheet action including all these maps in a “topological rigid string theory” was written by Hořava many years ago, but various subtleties arise when trying to use it for computations. In this talk, we will construct a Polyakov-like generalization of Hořava’s world sheet action that is well-defined, and we will show how it reproduces the free limit of the Yang-Mills theory, both by formal arguments and by explicitly computing its partition function in several cases. We will also discuss the generalization of this string theory with boundaries, corresponding to Wilson loops, and mention possible ways to generalize it for the finite-coupling gauge theory.
Posted by: Jesse van Muiden
Wed
4 Mar 2026
Scattering on the Coulomb Branch of N=4 SYM
📍 London
Kelian Haring
(University of Amsterdam)
Abstract:
I will discuss scattering on the Coulomb branch of planar N=4 SYM at finite ’t Hooft coupling. This describes a family of classical open-string S-matrices that smoothly interpolates between perturbative parton scattering at weak coupling and flat-space string scattering at strong coupling. I will focus on the four-point amplitude and discuss its remarkably rich structure: nonlinear Regge trajectories, dual conformal invariance, an intricate spectrum of bound states with an accumulation point, and a two-particle cut. Using dispersion relations and S-matrix bootstrap techniques, these properties can be incorporated to constrain the amplitude at finite ’t Hooft coupling, and I will discuss bounds on Wilson coefficients, couplings to bound states, and the overall shape of the amplitude.
This is based on https://arxiv.org/abs/2510.19909.
I will discuss scattering on the Coulomb branch of planar N=4 SYM at finite ’t Hooft coupling. This describes a family of classical open-string S-matrices that smoothly interpolates between perturbative parton scattering at weak coupling and flat-space string scattering at strong coupling. I will focus on the four-point amplitude and discuss its remarkably rich structure: nonlinear Regge trajectories, dual conformal invariance, an intricate spectrum of bound states with an accumulation point, and a two-particle cut. Using dispersion relations and S-matrix bootstrap techniques, these properties can be incorporated to constrain the amplitude at finite ’t Hooft coupling, and I will discuss bounds on Wilson coefficients, couplings to bound states, and the overall shape of the amplitude.
This is based on https://arxiv.org/abs/2510.19909.
Posted by: Andrew Svesko
Wed
4 Mar 2026
Entanglement Matters: Entanglement as an organizing principle of quantum matter
📍 London
Frank Verstraete
(U Cambridge)
Abstract:
"Entanglement as an organizing principle of quantum matter"
A century after the formulation of the Schrödinger equation, the exponential complexity of many-body systems remains the central challenge of modern physics. Entanglement theory has recently broken this stalemate through the development of tensor networks. This colloquium explores these methods as a powerful arsenal for simulating strongly correlated matter and will demonstrate their utility in identifying the emergent (generalized) symmetries that define and classify quantum phases.
see more info:
https://lims.ac.uk/
https://lims.ac.uk/event/entanglement-as-an-organising-principle-of-quantum-matter/
"Entanglement as an organizing principle of quantum matter"
A century after the formulation of the Schrödinger equation, the exponential complexity of many-body systems remains the central challenge of modern physics. Entanglement theory has recently broken this stalemate through the development of tensor networks. This colloquium explores these methods as a powerful arsenal for simulating strongly correlated matter and will demonstrate their utility in identifying the emergent (generalized) symmetries that define and classify quantum phases.
see more info:
https://lims.ac.uk/
https://lims.ac.uk/event/entanglement-as-an-organising-principle-of-quantum-matter/
Posted by: JUVEN WANG
Tue
3 Mar 2026
The Battle Against the Underdetermination of Dark Energy
📍 London
Pedro Ferreira
(Oxford)
Abstract:
Cosmological data has opened up new vistas on fundamental physics yet it is limited in its scope. While it has given us tantalizing hints at how the Universe might be expanding, it is unclear whether it can ever be used to find the microphysical structure of whatever is driving this expansion. I will discuss the evidence for what is, by far, the most thoroughly explored proposal - dynamical dark energy driven by a scalar field - pointing out what we can and cannot say about its fundamental nature. I will argue that it is unlikely (but not impossible) that it is normal quintessence, that there is strong evidence that there is some type of non-minimal coupling but which brings with it a host of undesirable consequences. I will try to look at the various loopholes and present what I think is the current status of cosmology as a probe of fundamental physics.
Cosmological data has opened up new vistas on fundamental physics yet it is limited in its scope. While it has given us tantalizing hints at how the Universe might be expanding, it is unclear whether it can ever be used to find the microphysical structure of whatever is driving this expansion. I will discuss the evidence for what is, by far, the most thoroughly explored proposal - dynamical dark energy driven by a scalar field - pointing out what we can and cannot say about its fundamental nature. I will argue that it is unlikely (but not impossible) that it is normal quintessence, that there is strong evidence that there is some type of non-minimal coupling but which brings with it a host of undesirable consequences. I will try to look at the various loopholes and present what I think is the current status of cosmology as a probe of fundamental physics.
Posted by: Sebastian Cespedes
Mon
2 Mar 2026
Lonti: classical and quantum energy conditions (3/4)
📍 London
Eleni Kontou
(KCL)
Abstract:
Energy conditions were originally formulated as pointwise bounds on contractions of the stress–energy tensor and have played a central role as assumptions in many foundational results of classical general relativity, most notably the singularity theorems. However, these conditions are generically violated by quantum fields, which admit states with locally negative energy density. Such violations are nevertheless constrained: quantum energy inequalities impose bounds on the magnitude and duration of negative energy.
In this course, I will first introduce the classical energy conditions and review their physical motivation and known violations. Then I will provide a brief introduction to quantum field theory on curved spacetimes and demonstrate how quantum energy inequalities can be derived. Finally, I will discuss in detail the average null energy condition and the limitations it imposes to causality violating spacetimes.
Course plan:
Lecture 1: Classical energy conditions and their violations
Lecture 2: Quantum field theory on curved spacetimes
Lecture 3: A derivation of a quantum energy inequality
Lecture 4: The average null energy condition
Energy conditions were originally formulated as pointwise bounds on contractions of the stress–energy tensor and have played a central role as assumptions in many foundational results of classical general relativity, most notably the singularity theorems. However, these conditions are generically violated by quantum fields, which admit states with locally negative energy density. Such violations are nevertheless constrained: quantum energy inequalities impose bounds on the magnitude and duration of negative energy.
In this course, I will first introduce the classical energy conditions and review their physical motivation and known violations. Then I will provide a brief introduction to quantum field theory on curved spacetimes and demonstrate how quantum energy inequalities can be derived. Finally, I will discuss in detail the average null energy condition and the limitations it imposes to causality violating spacetimes.
Course plan:
Lecture 1: Classical energy conditions and their violations
Lecture 2: Quantum field theory on curved spacetimes
Lecture 3: A derivation of a quantum energy inequality
Lecture 4: The average null energy condition
Posted by: Damian Galante
February 2026
Thu
26 Feb 2026
TBA
📍 London
Rafael Aoude
(Edinburgh)
Wed
25 Feb 2026
AI-Assisted Mathematical Discovery (Course)
📍 London
Nebius Academy
(Nebius)
Abstract:
This 14-week course explores how modern AI techniques can support mathematical research and problem-solving. It is not only an introduction to AI, but also a survey of its applications in math discovery, illustrated through research papers and coding tasks.
Course topics include:
- AI-assisted coding and reasoning. Running massive math experiments with the help of coding assistants. Using LLMs as research assistants.
- Training and using AI models. From linear models to neural networks: when AI models are useful and when they are not; data collection; model training.
- Transformers and LLMs. Mathematical data as sequences: from individual formulas to statements and proofs. The use of transformers and LLMs.
- Searching for examples and counterexamples. Speeding up search in huge search spaces. Algorithm optimization with AlphaEvolve and its open source analogs. Reinforcement Learning.
The course will be taught at the London Institute for Mathematical Sciences over 14 weeks, starting on February 25, with sessions held on Wednesdays from 10:00 am to 1:00 pm.
The programme is open to mathematicians and theoretical physicists, with proficiency in Python as a strong prerequisite.
For registration and more information on the course and Nebius Academy, visit: https://academy.nebius.com/ai-for-math?utm_source=lims&utm_medium=email&utm_campaign=limsnewsletter
This 14-week course explores how modern AI techniques can support mathematical research and problem-solving. It is not only an introduction to AI, but also a survey of its applications in math discovery, illustrated through research papers and coding tasks.
Course topics include:
- AI-assisted coding and reasoning. Running massive math experiments with the help of coding assistants. Using LLMs as research assistants.
- Training and using AI models. From linear models to neural networks: when AI models are useful and when they are not; data collection; model training.
- Transformers and LLMs. Mathematical data as sequences: from individual formulas to statements and proofs. The use of transformers and LLMs.
- Searching for examples and counterexamples. Speeding up search in huge search spaces. Algorithm optimization with AlphaEvolve and its open source analogs. Reinforcement Learning.
The course will be taught at the London Institute for Mathematical Sciences over 14 weeks, starting on February 25, with sessions held on Wednesdays from 10:00 am to 1:00 pm.
The programme is open to mathematicians and theoretical physicists, with proficiency in Python as a strong prerequisite.
For registration and more information on the course and Nebius Academy, visit: https://academy.nebius.com/ai-for-math?utm_source=lims&utm_medium=email&utm_campaign=limsnewsletter
Posted by: Evgeny Sobko
Wed
25 Feb 2026
Eigenfunctions from topological strings and supersymmetric gauge theories
📍 London
Matijn Francois
(Geneva University)
Abstract:
The topological string/spectral theory correspondence establishes a precise, non-perturbative duality between topological strings on local Calabi–Yau threefolds and the spectral theory of quantized mirror curves. This duality has been rigorously formulated for the closed string sector, but the open string sector is less understood. In this talk, I will explain how one can use open-string partition functions to construct eigenfunctions for the quantized mirror curves of local F0 = P1 x P1 and the Y(N, 0) geometries more generally. We will then discuss the four-dimensional limit, underlining the implications for spectral problems relating four-dimensional supersymmetric gauge theories to the quantization of their Seiberg–Witten curves. This gives exact, analytic eigenfunctions for a finite difference analogue of the Schrödinger equation.
The topological string/spectral theory correspondence establishes a precise, non-perturbative duality between topological strings on local Calabi–Yau threefolds and the spectral theory of quantized mirror curves. This duality has been rigorously formulated for the closed string sector, but the open string sector is less understood. In this talk, I will explain how one can use open-string partition functions to construct eigenfunctions for the quantized mirror curves of local F0 = P1 x P1 and the Y(N, 0) geometries more generally. We will then discuss the four-dimensional limit, underlining the implications for spectral problems relating four-dimensional supersymmetric gauge theories to the quantization of their Seiberg–Witten curves. This gives exact, analytic eigenfunctions for a finite difference analogue of the Schrödinger equation.
Posted by: Jesse van Muiden
Wed
25 Feb 2026
Near-extremal holographic correlators
📍 London
Blaise Gouteraux
(Ecole polytechnique)
Abstract:
Near-extremal black holes with an AdS2 throat are of great interest in string theory and in holography due to their ubiquity as classical gravitational saddles. The emergent SL(2,R) symmetry associated to the throat plays an important role in their low-temperature physics. In this talk, I will describe recent progress on analytically computing holographic correlators in black hole spacetimes with a near-extremal AdS2xR2 near-horizon geometry, focusing on current-current and shear correlators. By improving on previous matching calculations, I will show how it is possible to obtain analytical approximations to the correlators that interpolate between the hydrodynamic (frequencies small compared to the temperature) and the non-hydrodynamic low-temperature regimes. The expressions we obtain capture the hydrodynamic poles, the gapped poles controlled by the SL(2,R) symmetry of the AdS2 throat and the successive collisions with them. I will also comment on the appearance of zero temperature gapless poles in the spectrum and their relation to the SL(2,R) spectrum.
Near-extremal black holes with an AdS2 throat are of great interest in string theory and in holography due to their ubiquity as classical gravitational saddles. The emergent SL(2,R) symmetry associated to the throat plays an important role in their low-temperature physics. In this talk, I will describe recent progress on analytically computing holographic correlators in black hole spacetimes with a near-extremal AdS2xR2 near-horizon geometry, focusing on current-current and shear correlators. By improving on previous matching calculations, I will show how it is possible to obtain analytical approximations to the correlators that interpolate between the hydrodynamic (frequencies small compared to the temperature) and the non-hydrodynamic low-temperature regimes. The expressions we obtain capture the hydrodynamic poles, the gapped poles controlled by the SL(2,R) symmetry of the AdS2 throat and the successive collisions with them. I will also comment on the appearance of zero temperature gapless poles in the spectrum and their relation to the SL(2,R) spectrum.
Posted by: Andrew Svesko
Wed
25 Feb 2026
Supersymmetric Quantum Mechanics, Defects and Quantum K-theory
📍 East of England
Cyril Closset
(University of Birmingham)
Abstract:
I will present two recent results about supersymmetric quantum mechanics with 2 supercharges (1d N=2). First, I will explain new Seiberg-like dualities between 1d SQCD-like theories, which are distinct 1d gauge theories with the same supersymmetric ground states. Then I will discuss the coupling of 1d N=2 quivers to 3d N=2 gauge theories in the context of the GLSM/Quantum K-theory correspondence, explaining how such line defects engineer interesting objects (the so-called Schubert classes) in the quantum K-theory of partial flag varieties.
I will present two recent results about supersymmetric quantum mechanics with 2 supercharges (1d N=2). First, I will explain new Seiberg-like dualities between 1d SQCD-like theories, which are distinct 1d gauge theories with the same supersymmetric ground states. Then I will discuss the coupling of 1d N=2 quivers to 3d N=2 gauge theories in the context of the GLSM/Quantum K-theory correspondence, explaining how such line defects engineer interesting objects (the so-called Schubert classes) in the quantum K-theory of partial flag varieties.
Posted by: Julian Kupka
Tue
24 Feb 2026
Gravitational Radiation from Quantum Fields
📍 London
Donal O'Connell
(Edinburgh University)
Abstract:
The era of high-precision gravitational data requires a demanding new level of precision in gravitational theory. In this talk I will discuss the use of methods from quantum field theory to address the challenge. These methods reframe our theoretical approach to gravity, making gravity look like two copies of electrodynamics. We will see that the Schwarzschild metric is a "double copy" of the Coulomb charge, and that gravitational waveforms can be determined without ever using the Einstein equation.
The era of high-precision gravitational data requires a demanding new level of precision in gravitational theory. In this talk I will discuss the use of methods from quantum field theory to address the challenge. These methods reframe our theoretical approach to gravity, making gravity look like two copies of electrodynamics. We will see that the Schwarzschild metric is a "double copy" of the Coulomb charge, and that gravitational waveforms can be determined without ever using the Einstein equation.
Posted by: Sebastian Cespedes
Mon
23 Feb 2026
Lonti: classical and quantum energy conditions (2/4)
📍 London
Eleni Kontou
(KCL)
Abstract:
Energy conditions were originally formulated as pointwise bounds on contractions of the stress–energy tensor and have played a central role as assumptions in many foundational results of classical general relativity, most notably the singularity theorems. However, these conditions are generically violated by quantum fields, which admit states with locally negative energy density. Such violations are nevertheless constrained: quantum energy inequalities impose bounds on the magnitude and duration of negative energy.
In this course, I will first introduce the classical energy conditions and review their physical motivation and known violations. Then I will provide a brief introduction to quantum field theory on curved spacetimes and demonstrate how quantum energy inequalities can be derived. Finally, I will discuss in detail the average null energy condition and the limitations it imposes to causality violating spacetimes.
Course plan:
Lecture 1: Classical energy conditions and their violations
Lecture 2: Quantum field theory on curved spacetimes
Lecture 3: A derivation of a quantum energy inequality
Lecture 4: The average null energy condition
Energy conditions were originally formulated as pointwise bounds on contractions of the stress–energy tensor and have played a central role as assumptions in many foundational results of classical general relativity, most notably the singularity theorems. However, these conditions are generically violated by quantum fields, which admit states with locally negative energy density. Such violations are nevertheless constrained: quantum energy inequalities impose bounds on the magnitude and duration of negative energy.
In this course, I will first introduce the classical energy conditions and review their physical motivation and known violations. Then I will provide a brief introduction to quantum field theory on curved spacetimes and demonstrate how quantum energy inequalities can be derived. Finally, I will discuss in detail the average null energy condition and the limitations it imposes to causality violating spacetimes.
Course plan:
Lecture 1: Classical energy conditions and their violations
Lecture 2: Quantum field theory on curved spacetimes
Lecture 3: A derivation of a quantum energy inequality
Lecture 4: The average null energy condition
Posted by: Damian Galante
Mon
23 Feb 2026
High-Rank Structure Constants and Separation of Variables in Planar N=4 SYM
📍 London
Paul Ryan
(DESY)
Abstract:
Integrability in planar N=4 SYM has led to the development of the cutting-edge Quantum Spectral Curve (QSC), a Riemann-Hilbert problem for a handful of Q-functions which encode the spectrum of conformal dimensions. With the QSC the planar N=4 SYM spectral problem is solved - anyone with a laptop can compute the dimension of any operator at any coupling. In a handful of examples, structure constants have also been
shown to simplify enormously when expressed in terms of the QSC Q-functions, but no systematic derivation is available even at tree level.
Using recent advancements in the Separation of Variables program for high-rank integrable systems I will explain how to systematically obtain
the Q-function representation for tree-level structure constants in the SU(4) sector. Based on upcoming work with T. Bargheer, C. Bercini, and G. Lefundes.
Integrability in planar N=4 SYM has led to the development of the cutting-edge Quantum Spectral Curve (QSC), a Riemann-Hilbert problem for a handful of Q-functions which encode the spectrum of conformal dimensions. With the QSC the planar N=4 SYM spectral problem is solved - anyone with a laptop can compute the dimension of any operator at any coupling. In a handful of examples, structure constants have also been
shown to simplify enormously when expressed in terms of the QSC Q-functions, but no systematic derivation is available even at tree level.
Using recent advancements in the Separation of Variables program for high-rank integrable systems I will explain how to systematically obtain
the Q-function representation for tree-level structure constants in the SU(4) sector. Based on upcoming work with T. Bargheer, C. Bercini, and G. Lefundes.
Posted by: Carlos Bercini
Thu
19 Feb 2026
Magnusian: an integrated approach to gravitational dynamics
📍 London
Jung-Wook Kim
(CERN)
Abstract:
One of key theoretical inputs for gravitational wave detection is an analytic description of binary dynamics, which provides the foundation for constructing waveform models used to generate waveform templates for detection. The conventional approach to binary dynamics is to construct the effective two-body Hamiltonian, which provides the equations of motion of the binary source. Motivated by the eikonal approximation of 2-to-2 scattering amplitudes in particle physics, we propose to approach the binary dynamics using the Magnusian (eikonal generator), which can be considered as integrated equations of motion. How the new approach relates to post-Minkowskian gravity, and the potential benefits that the new approach may provide, will be discussed.
One of key theoretical inputs for gravitational wave detection is an analytic description of binary dynamics, which provides the foundation for constructing waveform models used to generate waveform templates for detection. The conventional approach to binary dynamics is to construct the effective two-body Hamiltonian, which provides the equations of motion of the binary source. Motivated by the eikonal approximation of 2-to-2 scattering amplitudes in particle physics, we propose to approach the binary dynamics using the Magnusian (eikonal generator), which can be considered as integrated equations of motion. How the new approach relates to post-Minkowskian gravity, and the potential benefits that the new approach may provide, will be discussed.
Posted by: Nathan Moynihan
Wed
18 Feb 2026
Gravitational Scattering in the Ultra-High-Energy Limit
📍 London
Emanuele Rosi
(Sapienza University and INFN Frascati, Rome)
Abstract:
The detection of gravitational waves (GW) after several decades from their formulation opened a new window to observe the universe. The new generation of GW detectors is expected to span a large parameter space, requiring theoretical physicist to develop different approaches to face the two-body problem in General Relativity, each of them based on some perturbative expansion, e.g. Post Newtonian, Post Minkowskian (PM), Self Force. Among these, Effective Field Theories and quantum amplitudes are used together to extract scattering observables which also have a meaningful classical limit, both in the PM and Self Force frameworks.
We analyse the high energy (Regge) regime of spinless two body scattering within this approach, by the prospect of isolating universal effects and to give insights on the resummation of the PM observables at higher orders, made possible by the simplicity of the calculations in the Regge limit. A sequence of classical Feynman diagrams is recognised to contribute to the leading power and leading log(s/t) in the high energy expansion. We compute them up to four loops (5PM) and use analyticity properties of the S-Matrix to maximise the information that we can extract at any PM order.
The detection of gravitational waves (GW) after several decades from their formulation opened a new window to observe the universe. The new generation of GW detectors is expected to span a large parameter space, requiring theoretical physicist to develop different approaches to face the two-body problem in General Relativity, each of them based on some perturbative expansion, e.g. Post Newtonian, Post Minkowskian (PM), Self Force. Among these, Effective Field Theories and quantum amplitudes are used together to extract scattering observables which also have a meaningful classical limit, both in the PM and Self Force frameworks.
We analyse the high energy (Regge) regime of spinless two body scattering within this approach, by the prospect of isolating universal effects and to give insights on the resummation of the PM observables at higher orders, made possible by the simplicity of the calculations in the Regge limit. A sequence of classical Feynman diagrams is recognised to contribute to the leading power and leading log(s/t) in the high energy expansion. We compute them up to four loops (5PM) and use analyticity properties of the S-Matrix to maximise the information that we can extract at any PM order.
Posted by: Riccardo Gonzo
Wed
18 Feb 2026
Black Holes, Holography and Singularities
📍 London
Andrei Parnachev
(Trinity College Dublin)
Abstract:
I will discuss thermal correlators in holographic CFTs. Using the operator product expansion, one can isolate a sector of the correlator which exhibits singularities. Some of these singularities are associated with the singularities of dual asymptotically AdS black holes, providing a useful window into the black hole interior.
I will discuss thermal correlators in holographic CFTs. Using the operator product expansion, one can isolate a sector of the correlator which exhibits singularities. Some of these singularities are associated with the singularities of dual asymptotically AdS black holes, providing a useful window into the black hole interior.
Posted by: Andrew Svesko
Wed
18 Feb 2026
Conformal field theory at finite temperature - from holography to asymptotic CFT data
📍 London
Ilija Buric
(Trinity College Dublin)
Abstract:
Consistency on manifolds other than flat space is known to constrain CFT data, as exemplified by Cardy’s celebrated formula for the asymptotic density of states. I will discuss some recent results coming from studying CFTs on thermal geometries in higher dimensions. In particular, I will show how multi-stress-tensor CFT data, known form the bulk, together with the KMS invariance of the thermal two-point function can be used to compute the latter in holographic theories. Time permitting, I will also discuss new asymptotic formulas for heavy-heavy-light OPE coefficients in generic three-dimensional CFTs.
Consistency on manifolds other than flat space is known to constrain CFT data, as exemplified by Cardy’s celebrated formula for the asymptotic density of states. I will discuss some recent results coming from studying CFTs on thermal geometries in higher dimensions. In particular, I will show how multi-stress-tensor CFT data, known form the bulk, together with the KMS invariance of the thermal two-point function can be used to compute the latter in holographic theories. Time permitting, I will also discuss new asymptotic formulas for heavy-heavy-light OPE coefficients in generic three-dimensional CFTs.
Posted by: Jesse van Muiden
Tue
17 Feb 2026
Beyond the Basics: The Messy Reality of Gravitational Wave Ringdowns
📍 London
Beatrice Bonga
(Radboud University.)
Abstract:
The past decade has completely transformed our understanding of what happens after black holes collide. What we once thought could be well-described by simple ringdowns—neat linear combinations of damped sinusoids (quasi-normal modes)—have turned out to be far richer and messier. Today we recognize ringdowns as an intricate tapestry woven from these quasinormal modes, nonlinear effects, tails, and secular phenomena like gravitational memory. In this talk, I’ll dive into the nonlinear aspects: where the theory stands today and some exciting recent observational claims that we might already be seeing these effects in GW250114. In the second half, I’ll switch gears to the early inspiral phase and tackle a practical question. Post-Newtonian theory is an asymptotic series, so at some point adding higher orders will yield less accurate results. Have we already reached this? By comparing PN to NR, we argue that we can still gain significant improvements by going to higher PN order, but that soon NR and PN will be equally accurate in the early inspiral.
The past decade has completely transformed our understanding of what happens after black holes collide. What we once thought could be well-described by simple ringdowns—neat linear combinations of damped sinusoids (quasi-normal modes)—have turned out to be far richer and messier. Today we recognize ringdowns as an intricate tapestry woven from these quasinormal modes, nonlinear effects, tails, and secular phenomena like gravitational memory. In this talk, I’ll dive into the nonlinear aspects: where the theory stands today and some exciting recent observational claims that we might already be seeing these effects in GW250114. In the second half, I’ll switch gears to the early inspiral phase and tackle a practical question. Post-Newtonian theory is an asymptotic series, so at some point adding higher orders will yield less accurate results. Have we already reached this? By comparing PN to NR, we argue that we can still gain significant improvements by going to higher PN order, but that soon NR and PN will be equally accurate in the early inspiral.
Posted by: Sebastian Cespedes
Mon
16 Feb 2026
Lonti: Classical and quantum energy conditions (1/4)
📍 London
Eleni Kontou
(KCL)
Abstract:
Energy conditions were originally formulated as pointwise bounds on contractions of the stress–energy tensor and have played a central role as assumptions in many foundational results of classical general relativity, most notably the singularity theorems. However, these conditions are generically violated by quantum fields, which admit states with locally negative energy density. Such violations are nevertheless constrained: quantum energy inequalities impose bounds on the magnitude and duration of negative energy.
In this course, I will first introduce the classical energy conditions and review their physical motivation and known violations. Then I will provide a brief introduction to quantum field theory on curved spacetimes and demonstrate how quantum energy inequalities can be derived. Finally, I will discuss in detail the average null energy condition and the limitations it imposes to causality violating spacetimes.
Course plan:
Lecture 1: Classical energy conditions and their violations
Lecture 2: Quantum field theory on curved spacetimes
Lecture 3: A derivation of a quantum energy inequality
Lecture 4: The average null energy condition
Energy conditions were originally formulated as pointwise bounds on contractions of the stress–energy tensor and have played a central role as assumptions in many foundational results of classical general relativity, most notably the singularity theorems. However, these conditions are generically violated by quantum fields, which admit states with locally negative energy density. Such violations are nevertheless constrained: quantum energy inequalities impose bounds on the magnitude and duration of negative energy.
In this course, I will first introduce the classical energy conditions and review their physical motivation and known violations. Then I will provide a brief introduction to quantum field theory on curved spacetimes and demonstrate how quantum energy inequalities can be derived. Finally, I will discuss in detail the average null energy condition and the limitations it imposes to causality violating spacetimes.
Course plan:
Lecture 1: Classical energy conditions and their violations
Lecture 2: Quantum field theory on curved spacetimes
Lecture 3: A derivation of a quantum energy inequality
Lecture 4: The average null energy condition
Posted by: Damian Galante
Thu
12 Feb 2026
Cosmic string for electromagnetic duality
📍 London
Shu-Heng Shao
(MIT)
Abstract:
We study novel conformal twist defects in 4d Maxwell theory, around which electric and magnetic fields are exchanged. These are codimension-2 defects living at the end of topological defects for certain non-invertible global symmetries. We determine the operator spectrum of the twist defect by solving classical electromagnetic wave equations subject to a twisted boundary condition. Using techniques from defect CFT, we show that correlation functions of these defect operators factorize into two sectors: a universal generalized free-field sector, and a chiral current sector analogous to edge modes in Chern-Simons theory. In a similar setup, we also revisit the twist fields attached to non-invertible line defects in the 2d compact boson CFT. We discuss a defect 't Hooft anomaly involving a chiral O(2) symmetry, highlighting its dynamical implications.
Info: https://lims.ac.uk/
We study novel conformal twist defects in 4d Maxwell theory, around which electric and magnetic fields are exchanged. These are codimension-2 defects living at the end of topological defects for certain non-invertible global symmetries. We determine the operator spectrum of the twist defect by solving classical electromagnetic wave equations subject to a twisted boundary condition. Using techniques from defect CFT, we show that correlation functions of these defect operators factorize into two sectors: a universal generalized free-field sector, and a chiral current sector analogous to edge modes in Chern-Simons theory. In a similar setup, we also revisit the twist fields attached to non-invertible line defects in the 2d compact boson CFT. We discuss a defect 't Hooft anomaly involving a chiral O(2) symmetry, highlighting its dynamical implications.
Info: https://lims.ac.uk/
Posted by: JUVEN WANG
Wed
11 Feb 2026
Non-Lorentzian Holography and Near-BPS Physics in String Theory
📍 East of England
Joseh Smith
(University of Birmingham)
Abstract:
In recent years there has been a renewed interest in understanding string theory close to BPS bounds using the tools of non-Lorentzian physics. In these regimes the underlying geometry is deformed, becoming a generalisation of Newton-Cartan geometry based around a brane-like foliation of spacetime. By considering such limits on both sides of a Lorentzian holographic duality we can construct dualities between non-Lorentzian QFT and string theory on non-Lorentzian spacetimes, which in the IR reduces to solutions of exotic non-Lorentzian supergravity theories. In this talk I will show how these theories, along with their BPS brane solutions, can be constructed using the explicit example of the M5-brane limit of eleven-dimensional supergravity. We will apply these lessons to D-brane limits from the perspective of both the gravitational solution and the worldvolume QFT to construct proposals for non-Lorentzian holography. We will see that both limits exhibit the same symmetry structure as the gravitational solutions, with the QFT dynamics reducing to motion on the moduli space of solitons representing quarter-BPS brane bound states. Time-permitting, I will finish with a discussion of upcoming work on including quantum effects on the QFT side using the example of Galilean Yang-Mills, which is proposed to be dual to non-relativistic string theory on a near-horizon D2-brane background.
In recent years there has been a renewed interest in understanding string theory close to BPS bounds using the tools of non-Lorentzian physics. In these regimes the underlying geometry is deformed, becoming a generalisation of Newton-Cartan geometry based around a brane-like foliation of spacetime. By considering such limits on both sides of a Lorentzian holographic duality we can construct dualities between non-Lorentzian QFT and string theory on non-Lorentzian spacetimes, which in the IR reduces to solutions of exotic non-Lorentzian supergravity theories. In this talk I will show how these theories, along with their BPS brane solutions, can be constructed using the explicit example of the M5-brane limit of eleven-dimensional supergravity. We will apply these lessons to D-brane limits from the perspective of both the gravitational solution and the worldvolume QFT to construct proposals for non-Lorentzian holography. We will see that both limits exhibit the same symmetry structure as the gravitational solutions, with the QFT dynamics reducing to motion on the moduli space of solitons representing quarter-BPS brane bound states. Time-permitting, I will finish with a discussion of upcoming work on including quantum effects on the QFT side using the example of Galilean Yang-Mills, which is proposed to be dual to non-relativistic string theory on a near-horizon D2-brane background.
Posted by: Julian Kupka
Wed
11 Feb 2026
Chiral anomalies and CPT
📍 London
Shu-Heng Shao
(MIT, Cambridge)
Abstract:
We discuss how the vector and axial U(1) symmetries of a massless Dirac fermion in 1+1d are realized in Hamiltonian lattice systems. Interestingly, these two lattice charges do not commute and form a non-abelian algebra, first discussed by Onsager. We prove that these symmetries force the low-energy theory to be massless, reminiscent of consequences from perturbative anomalies of continuous global symmetries in quantum field theory. This lattice anomaly is of order 2, but when a lattice CPT symmetry is further imposed, the anomaly becomes of infinite order (i.e., torsion-free), matching the continuum result.
We discuss how the vector and axial U(1) symmetries of a massless Dirac fermion in 1+1d are realized in Hamiltonian lattice systems. Interestingly, these two lattice charges do not commute and form a non-abelian algebra, first discussed by Onsager. We prove that these symmetries force the low-energy theory to be massless, reminiscent of consequences from perturbative anomalies of continuous global symmetries in quantum field theory. This lattice anomaly is of order 2, but when a lattice CPT symmetry is further imposed, the anomaly becomes of infinite order (i.e., torsion-free), matching the continuum result.
Posted by: Jesse van Muiden
Wed
11 Feb 2026
A universal sum over topologies in 3d gravity
📍 London
Lorenz Eberhardt
(University of Amsterdam)
Abstract:
I will describe recent progress toward a well-defined sum over topologies in AdS3 quantum gravity and its interpretation from the boundary perspective. A minimal set of consistency requirements on the boundary ensemble (crossing symmetry and typicality) is formulated and shown to admit a direct bulk realization in terms of elementary surgery moves on three-manifolds. These moves generate a large and unavoidable class of bulk geometries that must be included in any reasonable definition of the gravitational path integral. The resulting manifolds are always on-shell (hyperbolic), though the construction does not exhaust all hyperbolic topologies. I will illustrate the structure of the resulting sum with explicit examples, including handlebody-knots, and discuss implications for the ensemble interpretations of AdS3 gravity.
Based on joint work with A. Belin, S. Collier, D. Liska, and B. Post (arXiv:2601.07906).
I will describe recent progress toward a well-defined sum over topologies in AdS3 quantum gravity and its interpretation from the boundary perspective. A minimal set of consistency requirements on the boundary ensemble (crossing symmetry and typicality) is formulated and shown to admit a direct bulk realization in terms of elementary surgery moves on three-manifolds. These moves generate a large and unavoidable class of bulk geometries that must be included in any reasonable definition of the gravitational path integral. The resulting manifolds are always on-shell (hyperbolic), though the construction does not exhaust all hyperbolic topologies. I will illustrate the structure of the resulting sum with explicit examples, including handlebody-knots, and discuss implications for the ensemble interpretations of AdS3 gravity.
Based on joint work with A. Belin, S. Collier, D. Liska, and B. Post (arXiv:2601.07906).
Posted by: Jesse van Muiden
Thu
5 Feb 2026
Phases with Generalized Symmetries from the SymTFT
📍 London
Alison Warman
(University of Oxford)
Abstract:
Quantum London Seminar (LIMS+QMUL joint seminar)
–-
This talk will present the systematic exploration of quantum phases of matter with generalized (categorical) symmetries, by means of the "Symmetry Topological Field Theory" (SymTFT). After introducing the general framework, I will discuss novel examples, including intrinsically gapless phases (which cannot be deformed to gapped phases with analogous symmetry properties) and gapped phases in which the symmetry broken vacua carry distinct kinds of topological order. I will also illustrate how ideas and techniques from the SymTFT can be used to obtain new results in quantum information.
–-
For more info, please find https://lims.ac.uk/
Quantum London Seminar (LIMS+QMUL joint seminar)
–-
This talk will present the systematic exploration of quantum phases of matter with generalized (categorical) symmetries, by means of the "Symmetry Topological Field Theory" (SymTFT). After introducing the general framework, I will discuss novel examples, including intrinsically gapless phases (which cannot be deformed to gapped phases with analogous symmetry properties) and gapped phases in which the symmetry broken vacua carry distinct kinds of topological order. I will also illustrate how ideas and techniques from the SymTFT can be used to obtain new results in quantum information.
–-
For more info, please find https://lims.ac.uk/
Posted by: JUVEN WANG
Thu
5 Feb 2026
An open system approach to cosmology
📍 London
Enrico Pajer
(Cambridge)
Abstract:
Cosmological models and predictions rely extensively on the well-established field theory framework of particle physics. However, a qualitatively new challenge arises: cosmological systems inherently contain substances with poorly constrained macroscopic properties and entirely unknown microphysics, such as the inflaton sector, dark matter, and dark energy. This results in a rich array of novel phenomena, including dissipation, stochastic fluctuations, out-of-equilibrium dynamics, and non-unitary macroscopic evolution. Moreover, since gravitational observables are of primary interest, and gravity universally couples to all forms of matter, a closed-system approach would require precise description of all cosmic constituents—something feasible only in the simplest toy models. To address these challenges, I propose an open system approach to cosmology.
I begin with a pedagogical introduction to open quantum system techniques, formulated within the Schwinger-Keldysh path integral framework. Then, I present the open effective field theory of inflation as a general class of theories of single-field inflation in the presence of an unknown medium. This local dissipative single-field effective theory yields a new class of predictions for cosmological correlators, generalizing existing models. I then tackle the challenge of formulating general relativity in the presence of an unspecified medium. As a warmup, I present a Schwinger-Keldysh formulation of electromagnetism in a medium, incorporating dissipation and fluctuations while ensuring a consistent treatment of gauge symmetries within an open system framework. Building on these results, I introduce the general and systematic construction of dissipative extensions of general relativity and explore their implications for modeling open dark energy and the late-time evolution of the universe. Finally, I study the implications for the dissipative propagation of gravitational waves through the dark sector medium.
Cosmological models and predictions rely extensively on the well-established field theory framework of particle physics. However, a qualitatively new challenge arises: cosmological systems inherently contain substances with poorly constrained macroscopic properties and entirely unknown microphysics, such as the inflaton sector, dark matter, and dark energy. This results in a rich array of novel phenomena, including dissipation, stochastic fluctuations, out-of-equilibrium dynamics, and non-unitary macroscopic evolution. Moreover, since gravitational observables are of primary interest, and gravity universally couples to all forms of matter, a closed-system approach would require precise description of all cosmic constituents—something feasible only in the simplest toy models. To address these challenges, I propose an open system approach to cosmology.
I begin with a pedagogical introduction to open quantum system techniques, formulated within the Schwinger-Keldysh path integral framework. Then, I present the open effective field theory of inflation as a general class of theories of single-field inflation in the presence of an unknown medium. This local dissipative single-field effective theory yields a new class of predictions for cosmological correlators, generalizing existing models. I then tackle the challenge of formulating general relativity in the presence of an unspecified medium. As a warmup, I present a Schwinger-Keldysh formulation of electromagnetism in a medium, incorporating dissipation and fluctuations while ensuring a consistent treatment of gauge symmetries within an open system framework. Building on these results, I introduce the general and systematic construction of dissipative extensions of general relativity and explore their implications for modeling open dark energy and the late-time evolution of the universe. Finally, I study the implications for the dissipative propagation of gravitational waves through the dark sector medium.
Posted by: Nathan Moynihan
Wed
4 Feb 2026
Conformal Defects and RG flows
📍 London
Silvia Penati
(Milan Bicocca University)
Abstract:
Quantum field theories with defects play a ubiquitous role in theoretical physics, both for their potential applications and for the role played in the general classification of QFTs. Fixed points in the space of QFTs are represented by Conformal Field Theories with conformal defects. In this talk I will introduce a large plethora of one-dimensional defect CFTs in D=3 and study RG flows connecting them. Peculiar aspects like the existence of enriched flows and anomaly driven flows will be discussed. I will also consider defects at non-trivial framing and their connection with matrix model results.
Quantum field theories with defects play a ubiquitous role in theoretical physics, both for their potential applications and for the role played in the general classification of QFTs. Fixed points in the space of QFTs are represented by Conformal Field Theories with conformal defects. In this talk I will introduce a large plethora of one-dimensional defect CFTs in D=3 and study RG flows connecting them. Peculiar aspects like the existence of enriched flows and anomaly driven flows will be discussed. I will also consider defects at non-trivial framing and their connection with matrix model results.
Posted by: Jesse van Muiden
Wed
4 Feb 2026
A Semiclassical Approach to Neutral Heavy Operators in Conformal Field Theory
📍 London
Jahmall Bersini
(Albert Einstein Center for Fundamental Physics, Bern University)
Abstract:
We present a semiclassical framework for computing the scaling dimensions of heavy neutral composite operators in conformal field theories (CFTs), providing a controlled and intuitive approach that extends beyond standard perturbative and numerical methods. Using the state–operator correspondence, the problem is mapped to the semiclassical quantization of periodic, spatially homogeneous classical field configurations on the cylinder. The Wilson–Fisher fixed point of the ϕ4 theory serves as a primary case study, and we conclude with brief remarks on extensions to other CFTs. The talk is based on: 2408.01414 [hep-th], 2511.08276 [hep-th], 2512.23539 [hep-th].
We present a semiclassical framework for computing the scaling dimensions of heavy neutral composite operators in conformal field theories (CFTs), providing a controlled and intuitive approach that extends beyond standard perturbative and numerical methods. Using the state–operator correspondence, the problem is mapped to the semiclassical quantization of periodic, spatially homogeneous classical field configurations on the cylinder. The Wilson–Fisher fixed point of the ϕ4 theory serves as a primary case study, and we conclude with brief remarks on extensions to other CFTs. The talk is based on: 2408.01414 [hep-th], 2511.08276 [hep-th], 2512.23539 [hep-th].
Posted by: Andrew Svesko
Wed
4 Feb 2026
Creases and caustics on black hole event horizons
📍 London
Harvey Reall
(Cambridge)
Abstract:
The existence of an event horizon is the defining property of a black hole. I shall review the properties of event horizons and discuss various examples demonstrating that event horizons are not smooth in dynamical processes such as black hole formation or merger. I shall explain how non-smooth features of an event horizon can be classified into various types, such as creases and caustics. I shall classify "perestroikas" of these structures, in which they undergo a qualitative change at an instant of time. A crease perestroika gives an exact local description of the event horizon near the "instant of merger" of a black hole merger. Other crease perestroikas describe event horizon nucleation or collapse of a hole in a toroidal horizon. Caustic perestroikas provide a mechanism for smoothing the horizon.
The existence of an event horizon is the defining property of a black hole. I shall review the properties of event horizons and discuss various examples demonstrating that event horizons are not smooth in dynamical processes such as black hole formation or merger. I shall explain how non-smooth features of an event horizon can be classified into various types, such as creases and caustics. I shall classify "perestroikas" of these structures, in which they undergo a qualitative change at an instant of time. A crease perestroika gives an exact local description of the event horizon near the "instant of merger" of a black hole merger. Other crease perestroikas describe event horizon nucleation or collapse of a hole in a toroidal horizon. Caustic perestroikas provide a mechanism for smoothing the horizon.
Posted by: David Vegh
Wed
4 Feb 2026
Positive Geometry for Stringy Scalar Amplitudes
📍 East of England
Jonah Stalknecht
(Charles University)
Abstract:
The KLT double copy relates open string amplitudes to closed string amplitudes, which provides the string-theoretic version of the more familiar relation Gravity=(Yang-Mills)^2. This relation is mediated by the KLT Kernel. In field theory, this kernel is well-studied, and it is the inverse of a matrix of amplitudes in bi-adjoint scalar theory (BAS). These amplitudes have been central in many recent advances in the field of scattering amplitudes. Crucially, it is known that these amplitudes have a completely geometric description in terms of the ABHY associahedron.
By contrast, much less is known about the string theory KLT kernel. Its inverse defines some α'-completion of BAS amplitudes, and exhibits intrinsically stringy properties. In this talk, I will show that these 'stringy BAS' amplitudes also admit a description from positive geometry. We will see how the stringy features emerge from this geometric description. Furthermore, I will argue that this geometry also contains all pion amplitudes in the Non-Linear Sigma Model, as well as mixed pion/BAS amplitudes. This gives us a first glimpse into how the positive geometry framework can be used to capture truly stringy features, and can be extended beyond the realm of rational functions.
Based on: Phys.Rev.Lett. 136 (2026) 1, 011601 (https://journals.aps.org/prl/abstract/10.1103/lb5l-twsb), Arxiv: 2508.20161 (https://arxiv.org/abs/2508.20161)
The KLT double copy relates open string amplitudes to closed string amplitudes, which provides the string-theoretic version of the more familiar relation Gravity=(Yang-Mills)^2. This relation is mediated by the KLT Kernel. In field theory, this kernel is well-studied, and it is the inverse of a matrix of amplitudes in bi-adjoint scalar theory (BAS). These amplitudes have been central in many recent advances in the field of scattering amplitudes. Crucially, it is known that these amplitudes have a completely geometric description in terms of the ABHY associahedron.
By contrast, much less is known about the string theory KLT kernel. Its inverse defines some α'-completion of BAS amplitudes, and exhibits intrinsically stringy properties. In this talk, I will show that these 'stringy BAS' amplitudes also admit a description from positive geometry. We will see how the stringy features emerge from this geometric description. Furthermore, I will argue that this geometry also contains all pion amplitudes in the Non-Linear Sigma Model, as well as mixed pion/BAS amplitudes. This gives us a first glimpse into how the positive geometry framework can be used to capture truly stringy features, and can be extended beyond the realm of rational functions.
Based on: Phys.Rev.Lett. 136 (2026) 1, 011601 (https://journals.aps.org/prl/abstract/10.1103/lb5l-twsb), Arxiv: 2508.20161 (https://arxiv.org/abs/2508.20161)
Posted by: Julian Kupka
Tue
3 Feb 2026
Bridging Simulation and Inference: Numerical relativity informed Bayesian analyses
📍 London
Charlie Hoy
(University of Portsmouth)
Abstract:
Postponed!
Postponed!
Posted by: João Vilas Boas
Tue
3 Feb 2026
Chasing the Photon
📍 London
Tin Sulejmanpasic
(Durham)
Abstract:
Electromagnetism links phenomena across all scales, from atomic structure and chemistry to the physics through which we access the distant universe. In this talk, I will describe my own journey toward understanding the photon. We will try to understand what makes photons robustly massless, and see how they can arise from condensed strings or emerge in simple spin systems, including ones with little to no symmetry. Finally, we will speculate on possible UV completions of electromagnetic theories, and ask whether life could even exist in a universe without light.
Electromagnetism links phenomena across all scales, from atomic structure and chemistry to the physics through which we access the distant universe. In this talk, I will describe my own journey toward understanding the photon. We will try to understand what makes photons robustly massless, and see how they can arise from condensed strings or emerge in simple spin systems, including ones with little to no symmetry. Finally, we will speculate on possible UV completions of electromagnetic theories, and ask whether life could even exist in a universe without light.
Posted by: Sebastian Cespedes
January 2026
Thu
29 Jan 2026
On functional freedom and Penrose's critiques of string theory
📍 London
James Read
(Oxford University)
Abstract:
In his The Road to Reality as well as in his Fashion, Faith and Fantasy, Roger Penrose criticises string theory and its practitioners from a variety of angles ranging from conceptual, technical, and methodological objections to sociological observations about the string theoretic scientific community. In this talk, I assess Penrose’s conceptual/technical objections to string theory, focussing in particular upon those which invoke the notion of ‘functional freedom’.
In his The Road to Reality as well as in his Fashion, Faith and Fantasy, Roger Penrose criticises string theory and its practitioners from a variety of angles ranging from conceptual, technical, and methodological objections to sociological observations about the string theoretic scientific community. In this talk, I assess Penrose’s conceptual/technical objections to string theory, focussing in particular upon those which invoke the notion of ‘functional freedom’.
Posted by: Yang-Hui He
Thu
29 Jan 2026
Novel properties of QFTs with long-range interactions
📍 London
Luke Lippstreu
(Edinburgh)
Abstract:
Infrared divergences obscure key analytic properties of scattering amplitudes, exposing gaps in our understanding of unitarity, causality, and crossing symmetry in theories with long-range forces. In this talk, I will use a simple model to illustrate novel analytic features of long-range theories, including modifications to the connectedness structure of amplitudes and to the general optical theorem. Since the LSZ reduction formula does not apply to theories with long-range forces, I will also present a modified version of LSZ reduction for this model, which accounts for long-range interactions and yields IR-finite amplitudes without ambiguous scales or ill-defined integrals.
Infrared divergences obscure key analytic properties of scattering amplitudes, exposing gaps in our understanding of unitarity, causality, and crossing symmetry in theories with long-range forces. In this talk, I will use a simple model to illustrate novel analytic features of long-range theories, including modifications to the connectedness structure of amplitudes and to the general optical theorem. Since the LSZ reduction formula does not apply to theories with long-range forces, I will also present a modified version of LSZ reduction for this model, which accounts for long-range interactions and yields IR-finite amplitudes without ambiguous scales or ill-defined integrals.
Posted by: Nathan Moynihan
Wed
28 Jan 2026
Relativistic Field Theories for Interacting Classical Higher-Spin Particles
📍 London
Radu Roiban
(Penn State University)
Abstract:
The construction of an effective field theory describing the long-distance interactions of Kerr black holes remains elusive.
As a step in its direction, we discuss relativistic effective field theories (EFT) designed to capture the long-distance gravitational interactions of massive spinning particles. While "no-go" theorems severely constrain the formulation of interacting higher-spin theories, we argue that these challenges can be navigated in the classical limit through the use of spin coherent states.
These states naturally incorporate gapless excitations which turn out to provide a description for processes in which the magnitude of the spin vector evolves dynamically.
By appropriately choosing the couplings of the theory these modes can either be decoupled, as we show by analyzing 3-point, Compton, and two-body amplitudes, or tuned to describe specific systems. We discuss the broader applicability of this framework, showing that it captures certain supersymmetric black holes as well as the dynamics of Newtonian bound states under external probes. Finally, we discuss possible strategies to identify the definition of Kerr black holes in this framework.
The construction of an effective field theory describing the long-distance interactions of Kerr black holes remains elusive.
As a step in its direction, we discuss relativistic effective field theories (EFT) designed to capture the long-distance gravitational interactions of massive spinning particles. While "no-go" theorems severely constrain the formulation of interacting higher-spin theories, we argue that these challenges can be navigated in the classical limit through the use of spin coherent states.
These states naturally incorporate gapless excitations which turn out to provide a description for processes in which the magnitude of the spin vector evolves dynamically.
By appropriately choosing the couplings of the theory these modes can either be decoupled, as we show by analyzing 3-point, Compton, and two-body amplitudes, or tuned to describe specific systems. We discuss the broader applicability of this framework, showing that it captures certain supersymmetric black holes as well as the dynamics of Newtonian bound states under external probes. Finally, we discuss possible strategies to identify the definition of Kerr black holes in this framework.
Posted by: Jesse van Muiden
Wed
28 Jan 2026
New Bounds on Null Energy in Quantum Field Theories
📍 London
Andrew Rolph
(Vrije U., Brussels)
Abstract:
Energy plays a ubiquitous role in physics. Many physical classical field theories obey pointwise energy conditions, and these have played an important role in, for example, singularity theorems. However, for local, relativistic quantum field theories (QFTs), the study of energy is both richer and more precarious. In this talk, I will derive new families of quantum null energy inequalities (QNEIs), i.e. bounds on integrated null energy, in QFTs in two and higher dimensions. These are universal, state-independent lower bounds on semi-local integrals of the energy-momentum flux in a null direction, and the first of this kind for interacting theories in higher dimensions. Our ingredients include the quantum null energy condition (QNEC), strong subadditivity of von Neumann entropies, defect operator expansions, and the vacuum modular Hamiltonians of null intervals and strips. These results are new, fundamental constraints on null energy in quantum field theories.
Energy plays a ubiquitous role in physics. Many physical classical field theories obey pointwise energy conditions, and these have played an important role in, for example, singularity theorems. However, for local, relativistic quantum field theories (QFTs), the study of energy is both richer and more precarious. In this talk, I will derive new families of quantum null energy inequalities (QNEIs), i.e. bounds on integrated null energy, in QFTs in two and higher dimensions. These are universal, state-independent lower bounds on semi-local integrals of the energy-momentum flux in a null direction, and the first of this kind for interacting theories in higher dimensions. Our ingredients include the quantum null energy condition (QNEC), strong subadditivity of von Neumann entropies, defect operator expansions, and the vacuum modular Hamiltonians of null intervals and strips. These results are new, fundamental constraints on null energy in quantum field theories.
Posted by: Andrew Svesko
Tue
27 Jan 2026
Deep Learning based discovery of Integrable Systems
📍 London
Evgeny Sobko
(LIMS)
Abstract:
Integrable systems are exactly solvable models that play a central role in QFT, string theory and statistical physics offering an ideal setting for understanding complex physical phenomena and developing novel analytical methods. However, the discovery of new integrable systems remains a major open challenge due to the nonlinearity of the Yang–Baxter equation (YBE) that defines them, and the vastness of its solution space. Here we present the first AI-based framework that enables the discovery of new quantum integrable systems in exact analytical form. Our
method combines an ensemble of neural networks, trained to identify high-precision numerical solutions to the YBE, with an algebraic extraction procedure based on the Reshetikhin integrability condition, which reconstructs the corresponding Hamiltonian families analytically. When applied to spin chains with three- and four-dimensional site spaces, we discover hundreds of previously unknown integrable Hamiltonians. Remarkably, these Hamiltonians organize into rational algebraic varieties, and we conjecture that this rationality holds universally — revealing a previously unexplored connection between quantum integrability and algebraic geometry. By unlocking inte-
grable systems far beyond the reach of traditional methods, this AI-driven approach substantially
expands the landscape of exactly solvable models and opens a scalable path to further discoveries.
Integrable systems are exactly solvable models that play a central role in QFT, string theory and statistical physics offering an ideal setting for understanding complex physical phenomena and developing novel analytical methods. However, the discovery of new integrable systems remains a major open challenge due to the nonlinearity of the Yang–Baxter equation (YBE) that defines them, and the vastness of its solution space. Here we present the first AI-based framework that enables the discovery of new quantum integrable systems in exact analytical form. Our
method combines an ensemble of neural networks, trained to identify high-precision numerical solutions to the YBE, with an algebraic extraction procedure based on the Reshetikhin integrability condition, which reconstructs the corresponding Hamiltonian families analytically. When applied to spin chains with three- and four-dimensional site spaces, we discover hundreds of previously unknown integrable Hamiltonians. Remarkably, these Hamiltonians organize into rational algebraic varieties, and we conjecture that this rationality holds universally — revealing a previously unexplored connection between quantum integrability and algebraic geometry. By unlocking inte-
grable systems far beyond the reach of traditional methods, this AI-driven approach substantially
expands the landscape of exactly solvable models and opens a scalable path to further discoveries.
Posted by: Sebastian Cespedes
Thu
22 Jan 2026
The Gravitational Compton Amplitude
📍 London
Mathias Driesse
(Humboldt)
Abstract:
The gravitational Compton amplitude describes gravitational waves scattering off a single black hole and is therefore a one-body observable ideal for analyzing quadratic-in-curvature of generic (Kerr) black holes from an effective field theory point of view. Based on upcoming work together with Y. Fabian Bautista, Gustav Jakobsen, and Kays Haddad, in this talk, I will discuss what makes it worth studying and calculating explicitly. I briefly review elements of black hole perturbation theory, which is the UV theory that describes such objects. I will then explain how worldline quantum field theory (WQFT) is an ideally suited tool to calculate the amplitude, focusing on similarities between this and the gravitation two-body problem which has recently been pushed to four loops. Finally, I will illustrate our matching procedure between these two theories, which allows us to calculate the Love numbers of black holes, with a particular focus on the N-matrix (Magnusian).
The gravitational Compton amplitude describes gravitational waves scattering off a single black hole and is therefore a one-body observable ideal for analyzing quadratic-in-curvature of generic (Kerr) black holes from an effective field theory point of view. Based on upcoming work together with Y. Fabian Bautista, Gustav Jakobsen, and Kays Haddad, in this talk, I will discuss what makes it worth studying and calculating explicitly. I briefly review elements of black hole perturbation theory, which is the UV theory that describes such objects. I will then explain how worldline quantum field theory (WQFT) is an ideally suited tool to calculate the amplitude, focusing on similarities between this and the gravitation two-body problem which has recently been pushed to four loops. Finally, I will illustrate our matching procedure between these two theories, which allows us to calculate the Love numbers of black holes, with a particular focus on the N-matrix (Magnusian).
Posted by: Nathan Moynihan
Wed
21 Jan 2026
An introduction to Open System Methods for Cosmology
📍 London
Thomas Colas
(University of Cambridge)
Abstract:
Effective field theories in particle physics are typically developed for clean, isolated systems, yet many physical phenomena, from condensed matter to gravitating systems, involve noisy and dissipative environments. The Schwinger-Keldysh formalism provides a powerful framework for describing such non-equilibrium dynamics and has led to important advances in areas including black hole physics, dissipative hydrodynamics, non-equilibrium holography, and primordial cosmology. I will begin with a pedagogical introduction to open-quantum-system techniques formulated within the Schwinger–Keldysh path integral. I will show how symmetries, locality, and unitarity constrain dissipation and noise, and illustrate the framework by deriving the imprints of dissipative dynamics on primordial non-Gaussianities. I will conclude by discussing the challenge of formulating general relativity in the presence of an unspecified medium.
Effective field theories in particle physics are typically developed for clean, isolated systems, yet many physical phenomena, from condensed matter to gravitating systems, involve noisy and dissipative environments. The Schwinger-Keldysh formalism provides a powerful framework for describing such non-equilibrium dynamics and has led to important advances in areas including black hole physics, dissipative hydrodynamics, non-equilibrium holography, and primordial cosmology. I will begin with a pedagogical introduction to open-quantum-system techniques formulated within the Schwinger–Keldysh path integral. I will show how symmetries, locality, and unitarity constrain dissipation and noise, and illustrate the framework by deriving the imprints of dissipative dynamics on primordial non-Gaussianities. I will conclude by discussing the challenge of formulating general relativity in the presence of an unspecified medium.
Posted by: Riccardo Gonzo
Wed
21 Jan 2026
Scattering on the Coulomb Branch of \(\mathcal{N}=4\) SYM
📍 London
Kelian Haring
(University of Amsterdam)
Abstract:
I will discuss scattering on the Coulomb branch of planar N=4 SYM at finite ’t Hooft coupling. This describes a family of classical open-string S-matrices that smoothly interpolates between perturbative parton scattering at weak coupling and flat-space string scattering at strong coupling. I will focus on the four-point amplitude and discuss its remarkably rich structure: nonlinear Regge trajectories, dual conformal invariance, an intricate spectrum of bound states with an accumulation point, and a two-particle cut. Using dispersion relations and S-matrix bootstrap techniques, these properties can be incorporated to constrain the amplitude at finite ’t Hooft coupling, and I will discuss bounds on Wilson coefficients, couplings to bound states, and the overall shape of the amplitude.
This talk is based on https://arxiv.org/abs/2510.19909.
I will discuss scattering on the Coulomb branch of planar N=4 SYM at finite ’t Hooft coupling. This describes a family of classical open-string S-matrices that smoothly interpolates between perturbative parton scattering at weak coupling and flat-space string scattering at strong coupling. I will focus on the four-point amplitude and discuss its remarkably rich structure: nonlinear Regge trajectories, dual conformal invariance, an intricate spectrum of bound states with an accumulation point, and a two-particle cut. Using dispersion relations and S-matrix bootstrap techniques, these properties can be incorporated to constrain the amplitude at finite ’t Hooft coupling, and I will discuss bounds on Wilson coefficients, couplings to bound states, and the overall shape of the amplitude.
This talk is based on https://arxiv.org/abs/2510.19909.
Posted by: Jesse van Muiden
Wed
21 Jan 2026
Recent Progress on Axions from Calabi-Yau Compactifications: Observational Data Meets String Theory
📍 London
David Marsh
(King's College London)
Abstract:
The past few years have seen major advances in understanding the properties of axions in string theory. This progress is thanks to new computational tools that allow for fast and automated calculations with Calabi-Yau manifolds. I will describe the predictions string theory makes for axion masses, decay constants, and axion-photon couplings, and how these depend precisely on the topology of the Calabi-Yau. I will describe explicit constructions of millions of axiverse models on Calabi-Yaus with Hodge numbers up to 491, across the whole Kreuzer-Skarke database (and some results beyond this). Phenomenology computed includes: black hole superradiance, dark matter relic density, fuzzy dark matter, decaying heavy relics and the intergalactic medium, and the QCD axion mass. I will describe the correlation between QCD axion mass and topology, and how this makes it possible for axion "haloscope" experiments to experimentally infer Hodge numbers, divisor topologies, and moduli space loci. I demonstrate the statistical state of the art by computing a full forward model incorporating likelihoods from the cosmic microwave background and Lyman-alpha forest and find the maximum Bayesian posterior probability region on the moduli space of a given CY favoured by a resolution of the tension in these data by an ultralight axion composing 1% of the dark matter.
The past few years have seen major advances in understanding the properties of axions in string theory. This progress is thanks to new computational tools that allow for fast and automated calculations with Calabi-Yau manifolds. I will describe the predictions string theory makes for axion masses, decay constants, and axion-photon couplings, and how these depend precisely on the topology of the Calabi-Yau. I will describe explicit constructions of millions of axiverse models on Calabi-Yaus with Hodge numbers up to 491, across the whole Kreuzer-Skarke database (and some results beyond this). Phenomenology computed includes: black hole superradiance, dark matter relic density, fuzzy dark matter, decaying heavy relics and the intergalactic medium, and the QCD axion mass. I will describe the correlation between QCD axion mass and topology, and how this makes it possible for axion "haloscope" experiments to experimentally infer Hodge numbers, divisor topologies, and moduli space loci. I demonstrate the statistical state of the art by computing a full forward model incorporating likelihoods from the cosmic microwave background and Lyman-alpha forest and find the maximum Bayesian posterior probability region on the moduli space of a given CY favoured by a resolution of the tension in these data by an ultralight axion composing 1% of the dark matter.
Posted by: Andrew Svesko
Tue
20 Jan 2026
From black holes to solvable irrelevant deformations and back
📍 London
Monica Guica
(IPhT)
Abstract:
String theory has been remarkably successful in explaining the microscopic origin of the entropy of certain black holes, primarily supersymmetric ones. However, finding the microscopic description of more realistic black holes remains a challenging open problem. In this talk, I will review evidence suggesting that the microscopic description of near- and non-extremal black holes is governed by special irrelevant deformations of two-dimensional conformal field theories. I will then discuss the properties of a particular class of solvable irrelevant deformations of two-dimensional quantum field theories, known as TT– and JTˉJ\bar-deformed CFTs. Finally, I will discuss the lessons that recent progress in understanding these deformations offers for the microscopic description of general black holes.
String theory has been remarkably successful in explaining the microscopic origin of the entropy of certain black holes, primarily supersymmetric ones. However, finding the microscopic description of more realistic black holes remains a challenging open problem. In this talk, I will review evidence suggesting that the microscopic description of near- and non-extremal black holes is governed by special irrelevant deformations of two-dimensional conformal field theories. I will then discuss the properties of a particular class of solvable irrelevant deformations of two-dimensional quantum field theories, known as TT– and JTˉJ\bar-deformed CFTs. Finally, I will discuss the lessons that recent progress in understanding these deformations offers for the microscopic description of general black holes.
Posted by: Sebastian Cespedes
Thu
15 Jan 2026
Automorphic L-functions, primon gases and quantum cosmology
📍 London
Sean A. Hartnoll
(Cambridge U., DAMTP)
Abstract:
I will review how the equations of general relativity near a spacetime singularity map onto an arithmetic hyperbolic billiard dynamics. The semiclassical quantum states for this dynamics are Maaβ cusp forms on fundamental domains of modular groups. For example, gravity in four spacetime dimensions leads to PSL(2,Z) while five dimensional gravity leads to PSL(2,Z[w]), with Z[w] the Eisenstein integers. The automorphic forms can be expressed, in a dilatation (Mellin transformed) basis as L-functions. The Euler product representation of these L-functions indicates that these quantum states admit a dual interpretation as a "primon gas" partition function. I will describe some physically motivated mathematical questions that arise from these observations.
I will review how the equations of general relativity near a spacetime singularity map onto an arithmetic hyperbolic billiard dynamics. The semiclassical quantum states for this dynamics are Maaβ cusp forms on fundamental domains of modular groups. For example, gravity in four spacetime dimensions leads to PSL(2,Z) while five dimensional gravity leads to PSL(2,Z[w]), with Z[w] the Eisenstein integers. The automorphic forms can be expressed, in a dilatation (Mellin transformed) basis as L-functions. The Euler product representation of these L-functions indicates that these quantum states admit a dual interpretation as a "primon gas" partition function. I will describe some physically motivated mathematical questions that arise from these observations.
Posted by: Morteza S. Hosseini
Wed
14 Jan 2026
Solving the AdS3/CFT2 duality
📍 London
Alessandro Sfondrini
(Birmingham University)
Abstract:
The correspondence between strings on AdS3 and dual CFT2s is one of the cornerstones of holography since its very inception. In the last few years there has been a remarkable revival of activity and progress in understanding quantitatively (i.e., solving) this duality. In this blackboard talk, I will present a pedagogical review of this progress and point out the exciting challenges which lie ahead.
Reference literature: A recent review of the subject can be found in arXiv:2408.08414
The correspondence between strings on AdS3 and dual CFT2s is one of the cornerstones of holography since its very inception. In the last few years there has been a remarkable revival of activity and progress in understanding quantitatively (i.e., solving) this duality. In this blackboard talk, I will present a pedagogical review of this progress and point out the exciting challenges which lie ahead.
Reference literature: A recent review of the subject can be found in arXiv:2408.08414
Posted by: Jesse van Muiden
Tue
13 Jan 2026
TBA
📍 London
Aron Wall
(University of Cambridge)
Abstract:
TBA
TBA
Posted by: Sebastian Cespedes
Wed
7 Jan 2026
TBA
📍 London
Charles Thull
(City University of London)
Abstract:
TBA
TBA
Posted by: Jesse van Muiden