Triangle Seminars
December 2023
Tue
19 Dec 2023
Topological 5d N=2 Gauge Theory: Novel Floer Homologies, their Dualities, and an A-infinity Category of Three-Manifolds
๐ London
Meng-Chwan Tan
(Singapore Natl. U.)
Abstract:
This talk is about our latest work in [arXiv:2311.18302]. We shall show how one can define novel gauge-theoretic Floer homologies of four, three and two-manifolds that are associated with Vafa-Witten, Hitchin and complexified BF configurations, respectively, from the physics of a certain topologically-twisted 5d N=2 gauge theory. Via topological invariance and a 5d รขโฌลS-dualityรขโฌย, we shall derive novel Atiyah-Floer correspondences of these gauge-theoretic Floer homologies which relate them to symplectic intersection Floer homologies of Higgs bundles, and a web of relations involving their loop/toroidal group generalizations and their Langlands dual. Lastly, through a soliton string theory interpretation of the 5d theory, we shall derive a Fukaya-Seidel type A-infinity category of Hitchin configurations on three-manifolds and its Atiyah-Floer correspondence. We therefore furnish purely physical realizations and generalizations of the mathematical conjectures and constructions of Haydys [1], Wang [2] and Abouzaid-Manolescu [3], and more.
This talk is about our latest work in [arXiv:2311.18302]. We shall show how one can define novel gauge-theoretic Floer homologies of four, three and two-manifolds that are associated with Vafa-Witten, Hitchin and complexified BF configurations, respectively, from the physics of a certain topologically-twisted 5d N=2 gauge theory. Via topological invariance and a 5d รขโฌลS-dualityรขโฌย, we shall derive novel Atiyah-Floer correspondences of these gauge-theoretic Floer homologies which relate them to symplectic intersection Floer homologies of Higgs bundles, and a web of relations involving their loop/toroidal group generalizations and their Langlands dual. Lastly, through a soliton string theory interpretation of the 5d theory, we shall derive a Fukaya-Seidel type A-infinity category of Hitchin configurations on three-manifolds and its Atiyah-Floer correspondence. We therefore furnish purely physical realizations and generalizations of the mathematical conjectures and constructions of Haydys [1], Wang [2] and Abouzaid-Manolescu [3], and more.
Posted by: andrea
Thu
14 Dec 2023
A Positive Way to Scatter Strings and Particles
๐ London
Hadleigh Frost
(Oxford U.)
Abstract:
We present a new formulation of string and particle amplitudes that emerges from simple one-dimensional models. The key is a new way to parametrize the positive part of Teichmรยผller space. The formulation works at all orders in the perturbation series, including non-planar contributions to the amplitudes. The relationship between string and particle amplitudes is made manifest as a "tropical limit". The results are well adapted to studying the scattering of large numbers of particles or amplitudes at high loop order. The talk will in part cover results from arXiv:2309.15913, 2311.09284.
We present a new formulation of string and particle amplitudes that emerges from simple one-dimensional models. The key is a new way to parametrize the positive part of Teichmรยผller space. The formulation works at all orders in the perturbation series, including non-planar contributions to the amplitudes. The relationship between string and particle amplitudes is made manifest as a "tropical limit". The results are well adapted to studying the scattering of large numbers of particles or amplitudes at high loop order. The talk will in part cover results from arXiv:2309.15913, 2311.09284.
Posted by: QMW
Wed
13 Dec 2023
From conformal to confining QFTs
Ali Fatemiabhari
(Swansea University)
Abstract:
In this talk, I present new solutions for type IIB supergravity generated by an infinite family of uplifts from six-dimensional supergravity solutions. After compactification on a circle, I will discuss that these backgrounds are proposed to be holographically dual to confining Quantum Field Theories. In the high energies, field theories will approach the strongly coupled regime of 5d quiver gauge field theories. I also mention some observables like Wilson loops and Entanglement entropy to sketch the properties of the theories.
In this talk, I present new solutions for type IIB supergravity generated by an infinite family of uplifts from six-dimensional supergravity solutions. After compactification on a circle, I will discuss that these backgrounds are proposed to be holographically dual to confining Quantum Field Theories. In the high energies, field theories will approach the strongly coupled regime of 5d quiver gauge field theories. I also mention some observables like Wilson loops and Entanglement entropy to sketch the properties of the theories.
Posted by: IC2
Wed
13 Dec 2023
Bootstrapping Smooth Line Operators in Chern-Simons-Matter CFTs
๐ London
De-liang Zhong
(Imperial College, London)
Abstract:
We study Chern-Simons theories at large N with either bosonic or fermionic matter in the fundamental representation. We will show that for smooth conformal line operators, their spectrum and shape dependence can be effectively bootstrapped using minimal inputs.
We study Chern-Simons theories at large N with either bosonic or fermionic matter in the fundamental representation. We will show that for smooth conformal line operators, their spectrum and shape dependence can be effectively bootstrapped using minimal inputs.
Posted by: andrea
Tue
12 Dec 2023
The mass of simple and higher-order networks
๐ London
Ginestra Bianconi
(QMUL)
Abstract:
We propose a theoretical framework that explains how the mass of simple and higher-order networks emerges from their topology and geometry. We use the discrete topological Dirac operator to define an action for a massless self-interacting topological Dirac field inspired by the NambuรขโฌโJona-Lasinio model. The mass of the network is strictly speaking the mass of this topological Dirac field defined on the network; it results from the chiral symmetry breaking of the model and satisfies a self-consistent gap equation. Interestingly, it is shown that the mass of a network depends on its spectral properties, topology, and geometry. Due to the breaking of the matterรขโฌโantimatter symmetry observed for the harmonic modes of the discrete topological Dirac operator, two possible definitions of the network mass can be given. For both possible definitions, the mass of the network comes from a gap equation with the difference among the two definitions encoded in the value of the bare mass. Indeed, the bare mass can be determined either by the Betti number รยฒ0 or by the Betti number รยฒ1 of the network. We provide numerical results on the mass of different networks, including random graphs, scale-free, and real weighted collaboration networks. We also discuss the generalization of these results to higher-order networks, defining the mass of simplicial complexes. The observed dependence of the mass of the considered topological Dirac field with the topology and geometry of the network could lead to interesting physics in the scenario in which the considered Dirac field is coupled with a dynamical evolution of the underlying network structure.
We propose a theoretical framework that explains how the mass of simple and higher-order networks emerges from their topology and geometry. We use the discrete topological Dirac operator to define an action for a massless self-interacting topological Dirac field inspired by the NambuรขโฌโJona-Lasinio model. The mass of the network is strictly speaking the mass of this topological Dirac field defined on the network; it results from the chiral symmetry breaking of the model and satisfies a self-consistent gap equation. Interestingly, it is shown that the mass of a network depends on its spectral properties, topology, and geometry. Due to the breaking of the matterรขโฌโantimatter symmetry observed for the harmonic modes of the discrete topological Dirac operator, two possible definitions of the network mass can be given. For both possible definitions, the mass of the network comes from a gap equation with the difference among the two definitions encoded in the value of the bare mass. Indeed, the bare mass can be determined either by the Betti number รยฒ0 or by the Betti number รยฒ1 of the network. We provide numerical results on the mass of different networks, including random graphs, scale-free, and real weighted collaboration networks. We also discuss the generalization of these results to higher-order networks, defining the mass of simplicial complexes. The observed dependence of the mass of the considered topological Dirac field with the topology and geometry of the network could lead to interesting physics in the scenario in which the considered Dirac field is coupled with a dynamical evolution of the underlying network structure.
Posted by: QMW
Fri
8 Dec 2023
Entanglement bootstrap for gapped topological phases II
๐ London
Bowen Shi
(UCSD)
Abstract:
In the 2nd lecture, we dig into the underlying logic of entanglement bootstrap. Illustrative examples are aimed to be simple but nontrivial. The following will be included: (1) We explain a few basic uses of strong subadditivity and quantum Markov states; we explain why axiom A0 is crucial to protect coherence. We derive the information convex set of the sphere as an application. (2) Related to the information convex set of the annulus, we explain the definition of quantum dimensions, why the vacuum has the smallest entropy, and why a certain "merged state" has the maximum entropy. (3) We classify immersed annuli on a sphere and explain why some puzzles of figure-8 annulus are not solved in naive ways. (4) In the context the reference state has a 0-form symmetry, we sketch a way to create a symmetry defect line, which (in some models) permutes anyons. This lecture is given using an ipad and is, thus, flexible. We also discuss topics from questions (feedbacks) during the 1st (and 2nd) lecture. See https://www.london-tqft.co.uk for details.
In the 2nd lecture, we dig into the underlying logic of entanglement bootstrap. Illustrative examples are aimed to be simple but nontrivial. The following will be included: (1) We explain a few basic uses of strong subadditivity and quantum Markov states; we explain why axiom A0 is crucial to protect coherence. We derive the information convex set of the sphere as an application. (2) Related to the information convex set of the annulus, we explain the definition of quantum dimensions, why the vacuum has the smallest entropy, and why a certain "merged state" has the maximum entropy. (3) We classify immersed annuli on a sphere and explain why some puzzles of figure-8 annulus are not solved in naive ways. (4) In the context the reference state has a 0-form symmetry, we sketch a way to create a symmetry defect line, which (in some models) permutes anyons. This lecture is given using an ipad and is, thus, flexible. We also discuss topics from questions (feedbacks) during the 1st (and 2nd) lecture. See https://www.london-tqft.co.uk for details.
Posted by: QMW
Thu
7 Dec 2023
Classifying Modular Graph Forms and their Integration over the Fundamental Domain
๐ London
Mehregan Doroudiani
(AEI Postdam)
Abstract:
In the calculation of the perturbative amplitude of superstring theory at one loop, modular graph functions (MGFs) emerge as notable mathematical constructs. These MGFs, representing Feynman diagrams on the surface of a torus, must be integrated over the fundamental domain. My talk will introduce MGFs, elucidate their generating series, and delve into the concept of equivariance, playing a key role in classifying MGFs. Additionally, I will cover recent advancements in understanding the generating series of MGFs and the integration of MGFs over the fundamental domain.
In the calculation of the perturbative amplitude of superstring theory at one loop, modular graph functions (MGFs) emerge as notable mathematical constructs. These MGFs, representing Feynman diagrams on the surface of a torus, must be integrated over the fundamental domain. My talk will introduce MGFs, elucidate their generating series, and delve into the concept of equivariance, playing a key role in classifying MGFs. Additionally, I will cover recent advancements in understanding the generating series of MGFs and the integration of MGFs over the fundamental domain.
Posted by: QMW
Wed
6 Dec 2023
Wilson Loop Duality and OPE for Form Factors of Half-BPS Operators
๐ London
Benjamin Basso
(LPENS, Paris)
Abstract:
I will explain how to describe form factors of single-trace half-BPS operators in planar N=4 super Yang Mills theory using the T-dual Wilson loop picture. After reviewing earlier results for operators in the stress-tensor multiplet, I will present the dual Wilson loop description for the so-called MHV form factors of half-BPS operators. The general proposal relates these form factors to the matrix elements of a null periodic super Wilson loop with outgoing states composed of zero-momentum scalars. I will present perturbative tests of this description at weak coupling. I will then explain how to obtain exact result at finite coupling in the collinear limit using the Wilson loop Operator Product Expansion. I will conclude with general comments and speculations about form factors of unprotected operators such as the Konishi operator.
I will explain how to describe form factors of single-trace half-BPS operators in planar N=4 super Yang Mills theory using the T-dual Wilson loop picture. After reviewing earlier results for operators in the stress-tensor multiplet, I will present the dual Wilson loop description for the so-called MHV form factors of half-BPS operators. The general proposal relates these form factors to the matrix elements of a null periodic super Wilson loop with outgoing states composed of zero-momentum scalars. I will present perturbative tests of this description at weak coupling. I will then explain how to obtain exact result at finite coupling in the collinear limit using the Wilson loop Operator Product Expansion. I will conclude with general comments and speculations about form factors of unprotected operators such as the Konishi operator.
Posted by: andrea
Tue
5 Dec 2023
A Bosonic Model of Quantum Holography
๐ London
Brian Swingle
(U. Maryland)
Abstract:
We analyze a model of qubits which we argue has an emergent quantum gravitational description similar to the fermionic Sachdev-Ye-Kitaev (SYK) model. The model is generic in that it includes all possible q-body couplings, lacks most symmetries, and has no spatial structure, so our results can be construed as establishing a certain ubiquity of quantum holography in systems dominated by many-body interactions. We will discuss implications for Hamiltonian complexity, the factorization problem in quantum gravity, and quantum simulations of holography. Based on 2311.01516 with Mike Winer.
We analyze a model of qubits which we argue has an emergent quantum gravitational description similar to the fermionic Sachdev-Ye-Kitaev (SYK) model. The model is generic in that it includes all possible q-body couplings, lacks most symmetries, and has no spatial structure, so our results can be construed as establishing a certain ubiquity of quantum holography in systems dominated by many-body interactions. We will discuss implications for Hamiltonian complexity, the factorization problem in quantum gravity, and quantum simulations of holography. Based on 2311.01516 with Mike Winer.
Posted by: QMW
Mon
4 Dec 2023
Finding isomorphic superconformal field theories
Monica Kang
(Caltech)
Abstract:
When do two different looking quantum field theories describe the same physics? This is essentially asking when the quantum field theories are isomorphic. In the case of topological quantum field theories, there are sometimes a way to determine them via topological invariants. For a superconformal field theory, what would be the minimal set of รขโฌลinvariantsรขโฌย to determine when they are isomorphic? I will discuss some approaches to this question in the context of superconformal field theories in four and six dimensions. Utilizing 4d class S theories that also admits 6d (1,0) SCFT origins, I will explain how a certain class of 4d N=2 SCFTs, which a priori look like distinct theories, can be shown to describe the same physics. I will further explain how the 6d (1,0) origin sheds light on the 3d duality.
When do two different looking quantum field theories describe the same physics? This is essentially asking when the quantum field theories are isomorphic. In the case of topological quantum field theories, there are sometimes a way to determine them via topological invariants. For a superconformal field theory, what would be the minimal set of รขโฌลinvariantsรขโฌย to determine when they are isomorphic? I will discuss some approaches to this question in the context of superconformal field theories in four and six dimensions. Utilizing 4d class S theories that also admits 6d (1,0) SCFT origins, I will explain how a certain class of 4d N=2 SCFTs, which a priori look like distinct theories, can be shown to describe the same physics. I will further explain how the 6d (1,0) origin sheds light on the 3d duality.
Posted by: IC2
Mon
4 Dec 2023
Krylov perspective on Modular Hamiltonians and QCD.
๐ London
Pawel Caputa
(U. Warsaw)
Abstract:
I will discuss some of the recent developments in the Krylov complexity. In particular, I will focus on the applications of the Krylov basis techniques to the modular Hamiltonian evolution and I will discuss a new angle on entanglement entropy in QCD at high energies. Based on arXiv:2306.14732 [hep-th] and work in progress.
I will discuss some of the recent developments in the Krylov complexity. In particular, I will focus on the applications of the Krylov basis techniques to the modular Hamiltonian evolution and I will discuss a new angle on entanglement entropy in QCD at high energies. Based on arXiv:2306.14732 [hep-th] and work in progress.
Posted by: andrea
Mon
4 Dec 2023
Entanglement bootstrap for gapped topological phases
๐ London
Bowen Shi
(UCSD)
Abstract:
Topological quantum field theory can emerge in gapped many-body quantum systems at low energies. In 2+1D systems, anyons can emerge, and in 3+1D, emergent excitations, including point-particles and loops-like excitations, possibly knotted or linked. In this lecture, we introduce an ongoing effort to understand (in fact, derive) laws of the emergent theory in 2+1D, 3+1D, (and higher D) gapped systems from a few axioms about the entanglement of a many-body ground state wave function. This research program, referred to as entanglement bootstrap, is an approach independent of quantum field theory, and it uses nontrivial quantum information and topology ideas. We explain the axioms and key concepts. We sketch the proof of several main theorems, including the definition of superselection sectors (anyons in 2+1D, point and loop excitations in 3+1D), the fusion spaces, and their constraints. We explain why immersion (i.e., local embedding) is valuable for, e.g., putting systems on closed space manifolds and what we hope to learn next. (see https://www.london-tqft.co.uk for more details)
Topological quantum field theory can emerge in gapped many-body quantum systems at low energies. In 2+1D systems, anyons can emerge, and in 3+1D, emergent excitations, including point-particles and loops-like excitations, possibly knotted or linked. In this lecture, we introduce an ongoing effort to understand (in fact, derive) laws of the emergent theory in 2+1D, 3+1D, (and higher D) gapped systems from a few axioms about the entanglement of a many-body ground state wave function. This research program, referred to as entanglement bootstrap, is an approach independent of quantum field theory, and it uses nontrivial quantum information and topology ideas. We explain the axioms and key concepts. We sketch the proof of several main theorems, including the definition of superselection sectors (anyons in 2+1D, point and loop excitations in 3+1D), the fusion spaces, and their constraints. We explain why immersion (i.e., local embedding) is valuable for, e.g., putting systems on closed space manifolds and what we hope to learn next. (see https://www.london-tqft.co.uk for more details)
Posted by: QMW
November 2023
Thu
30 Nov 2023
Gravitational observatories
๐ London
Damian Galante
(King's College)
Abstract:
We discuss the initial boundary value problem in general relativity (with vanishing cosmological constant). We consider a non-standard set of boundary conditions, known as conformal boundary conditions, where the conformal class of the induced metric and the trace of the extrinsic curvature are fixed at the boundary. We compare these results with analogous results for the Dirichlet problem both in Lorentzian and Euclidean signature, where a notion of conformal black hole thermodynamics will be developed. Time permitting, we will discuss implications for holography and de Sitter space.
We discuss the initial boundary value problem in general relativity (with vanishing cosmological constant). We consider a non-standard set of boundary conditions, known as conformal boundary conditions, where the conformal class of the induced metric and the trace of the extrinsic curvature are fixed at the boundary. We compare these results with analogous results for the Dirichlet problem both in Lorentzian and Euclidean signature, where a notion of conformal black hole thermodynamics will be developed. Time permitting, we will discuss implications for holography and de Sitter space.
Posted by: QMW
Wed
29 Nov 2023
Higher-order gravities: What they are and what they are for
Angel Murcia
(University of Padova)
Abstract:
Higher-order gravities are extensions of General Relativity (GR) which introduce in the classical action terms of higher order in the curvature. These appear naturally in the context of string effective actions, as well as in generic gravitational EFTs. Among the myriads of higher-order gravities one may think of, in this talk I will focus on specific theories whose equations of motion are of second order in derivatives for some particular backgrounds. I will provide many examples of such theories, classification results and argue that a subclass of them actually forms a basis for the space of gravitational EFTs. Afterwards, I will discuss the addition of non-minimal couplings to matter, show that some of these theories possess fully regular black hole solutions and conclude with some holographic applications.
Higher-order gravities are extensions of General Relativity (GR) which introduce in the classical action terms of higher order in the curvature. These appear naturally in the context of string effective actions, as well as in generic gravitational EFTs. Among the myriads of higher-order gravities one may think of, in this talk I will focus on specific theories whose equations of motion are of second order in derivatives for some particular backgrounds. I will provide many examples of such theories, classification results and argue that a subclass of them actually forms a basis for the space of gravitational EFTs. Afterwards, I will discuss the addition of non-minimal couplings to matter, show that some of these theories possess fully regular black hole solutions and conclude with some holographic applications.
Posted by: IC2
Wed
29 Nov 2023
Harmonic analysis and the conformal bootstrap reloaded
๐ London
Dalimil Mazac
(IPhT, Saclay)
Abstract:
I will discuss a connection between harmonic analysis on hyperbolic n-manifolds and conformal field theory in n-1 dimensions. Used in one direction, this connection leads to new spectral bounds on hyperbolic manifolds. Used in the other direction, it offers a new viewpoint on the spectra data of conformal field theories.
I will discuss a connection between harmonic analysis on hyperbolic n-manifolds and conformal field theory in n-1 dimensions. Used in one direction, this connection leads to new spectral bounds on hyperbolic manifolds. Used in the other direction, it offers a new viewpoint on the spectra data of conformal field theories.
Posted by: andrea
Tue
28 Nov 2023
On a geometrisation of generalised symmetries
๐ London
Andrea Ferrari
(Edinburg and DESY)
Abstract:
There has recently been a lot of activity in the field of generalised symmetries. In the context of supersymmetric gauge theories with interesting moduli spaces of vacua, such as 3d N=4 theories, global symmetries may enjoy a geometric interpretation: they act as isometries of the moduli space. In this talk I will informally put forward the idea that by enhancing the notion of moduli space one can in a similar fashion geometrise generalised symmetries. I will focus on simple 3d N=4 abelian example and talk about various things including what I'll call 0- and 1-form resolutions as well as automorphism 2-groups.
There has recently been a lot of activity in the field of generalised symmetries. In the context of supersymmetric gauge theories with interesting moduli spaces of vacua, such as 3d N=4 theories, global symmetries may enjoy a geometric interpretation: they act as isometries of the moduli space. In this talk I will informally put forward the idea that by enhancing the notion of moduli space one can in a similar fashion geometrise generalised symmetries. I will focus on simple 3d N=4 abelian example and talk about various things including what I'll call 0- and 1-form resolutions as well as automorphism 2-groups.
Posted by: QMW
Fri
24 Nov 2023
Bootstrapping Bulk Locality
๐ London
Nat Levine
(ENS Paris)
Abstract:
I will present the problem of building local AdS bulk observables from boundary CFT data. Focusing on QFTs coupled to a rigid AdS background, we study the analyticity constraints that bulk locality imposes on bulk-boundary-boundary 3-point functions ("AdS form factors"). We reformulate these constraints as a complete, non-perturbative set of sum rules. These sum rules lead to additional constraints on the boundary CFT on top of crossing, and can be implemented numerically in the bootstrap. We study the flat limit when these "AdS form factors" become form factors. (Based on 2305.07078)
I will present the problem of building local AdS bulk observables from boundary CFT data. Focusing on QFTs coupled to a rigid AdS background, we study the analyticity constraints that bulk locality imposes on bulk-boundary-boundary 3-point functions ("AdS form factors"). We reformulate these constraints as a complete, non-perturbative set of sum rules. These sum rules lead to additional constraints on the boundary CFT on top of crossing, and can be implemented numerically in the bootstrap. We study the flat limit when these "AdS form factors" become form factors. (Based on 2305.07078)
Posted by: QMW
Thu
23 Nov 2023
Equivalence of 1-loop RG flows in 4d Chern-Simons and integrable 2d sigma-models
Nat Levine
(ENS Paris)
Abstract:
Costello, Witten and Yamazaki proposed a 4d Chern-Simons theory as a unified way to engineer integrable models. In the presence of 'Disorder' defects (for non-ultralocal 2d theories), this correspondence has been established only classically. As a first quantum check, I will derive the matching of 1-loop divergences between the 4d and 2d theories. My assumptions are general and seem to isolate sigma-models among the 2d theories. (Based on 2309.16753)
Costello, Witten and Yamazaki proposed a 4d Chern-Simons theory as a unified way to engineer integrable models. In the presence of 'Disorder' defects (for non-ultralocal 2d theories), this correspondence has been established only classically. As a first quantum check, I will derive the matching of 1-loop divergences between the 4d and 2d theories. My assumptions are general and seem to isolate sigma-models among the 2d theories. (Based on 2309.16753)
Posted by: IC2
Thu
23 Nov 2023
Lonti: The initial (boundary) value problem in numerical general relativity
Pau Figueras
(QMUL)
Abstract:
In these series of lectures we will explore initial value problem in general relativity and how it can be solved in a computer in practical situations. We will first cover the necessary mathematical foundations, including the concepts of well-posedness and strong hyperbolicity, and then explore the current formulations of Einsteinรขโฌโขs theory of gravity that are implemented in modern numerical codes, namely generalised harmonic coordinates and the BSSN formulation. We shall see how the latter can be implemented in a toy code so as to get some hands on experience. Time permitting, we will also explore the initial boundary value problem in asymptotically anti-de Sitter spaces and how it can be solved in practice using the characteristic formulation of the Einstein equations in applications of holography.
In these series of lectures we will explore initial value problem in general relativity and how it can be solved in a computer in practical situations. We will first cover the necessary mathematical foundations, including the concepts of well-posedness and strong hyperbolicity, and then explore the current formulations of Einsteinรขโฌโขs theory of gravity that are implemented in modern numerical codes, namely generalised harmonic coordinates and the BSSN formulation. We shall see how the latter can be implemented in a toy code so as to get some hands on experience. Time permitting, we will also explore the initial boundary value problem in asymptotically anti-de Sitter spaces and how it can be solved in practice using the characteristic formulation of the Einstein equations in applications of holography.
Posted by: andrea
Thu
23 Nov 2023
Exact TTbar deformation of 2d Yang-Mills theory
๐ London
Rodolfo Panerai
(Cologne U.)
Abstract:
The TTbar deformation is an irrelevant deformation of 2D field theories
associated with nonlocal UV behaviour. Despite its apparent solvability, many
aspects of the deformation remain mysterious.
In this talk, I will present exact results for the TTbar deformation of 2D
U(N) Yang-Mills theory.
Carrying out the analysis at the level of each instanton sector, we can
determine the nonperturbative contributions to the partition function and
prove that the spectrum undergoes a truncation (a property only conjectured
for other TTbar-deformed theories).
We then derive the large-N limit by studying the relevant flow equation,
uncovering a rich phase diagram where phase transitions are driven by
instanton condensation.
The TTbar deformation is an irrelevant deformation of 2D field theories
associated with nonlocal UV behaviour. Despite its apparent solvability, many
aspects of the deformation remain mysterious.
In this talk, I will present exact results for the TTbar deformation of 2D
U(N) Yang-Mills theory.
Carrying out the analysis at the level of each instanton sector, we can
determine the nonperturbative contributions to the partition function and
prove that the spectrum undergoes a truncation (a property only conjectured
for other TTbar-deformed theories).
We then derive the large-N limit by studying the relevant flow equation,
uncovering a rich phase diagram where phase transitions are driven by
instanton condensation.
Posted by: QMW
Wed
22 Nov 2023
Conformal boundary conditions, Cardy's variational ansatz and phase structure of 2D QFTs
๐ London
Anatoly Konechny
(Heriot-Watt)
Abstract:
We will consider perturbations of 2D CFTs by multiple relevant operators. The massive phases of such perturbations can be labeled by conformal boundary conditions. Cardy's variational ansatz approximates the vacuum state of the perturbed theory by a smeared conformal boundary state. In this talk we will discuss the limitations and propose generalisations of this ansatz using both analytic and numerical insights based on TCSA.
In particular we analyse the stability of Cardy's ansatz states with respect to boundary relevant perturbations using bulk-boundary OPE coefficients. We show that certain transitions between the massive phases arise from a pair of boundary RG flows. The RG flows start from the conformal boundary on the transition surface and end on those that lie on the two sides of it. As an example we work out the details of the phase diagram for the Ising field theory and for the tricritical Ising model perturbed by the leading thermal and magnetic fields. Based on arXiv:2306.13719.
We will consider perturbations of 2D CFTs by multiple relevant operators. The massive phases of such perturbations can be labeled by conformal boundary conditions. Cardy's variational ansatz approximates the vacuum state of the perturbed theory by a smeared conformal boundary state. In this talk we will discuss the limitations and propose generalisations of this ansatz using both analytic and numerical insights based on TCSA.
In particular we analyse the stability of Cardy's ansatz states with respect to boundary relevant perturbations using bulk-boundary OPE coefficients. We show that certain transitions between the massive phases arise from a pair of boundary RG flows. The RG flows start from the conformal boundary on the transition surface and end on those that lie on the two sides of it. As an example we work out the details of the phase diagram for the Ising field theory and for the tricritical Ising model perturbed by the leading thermal and magnetic fields. Based on arXiv:2306.13719.
Posted by: andrea
Wed
22 Nov 2023
Finite-N Black Hole Cohomologies
Siyul Lee
(Michigan University)
Abstract:
We study new cohomologies for the BPS operators of the N=4 Yang-Mills theory with SU(2), SU(3) and SU(4) gauge groups. The goal of this programme is to identify the black hole microstates in the dual field theory that are successfully counted by the index to match the Bekenstein-Hawking entropy. We first study the index over non-graviton cohomologies and identify their threshold levels. We present examples of the non-graviton operators in the SU(2) theory and in a subsector of the SU(3) theory that corresponds to the BMN matrix model. We also present an ansatz that can be used to construct these operators. Finally, we discuss non-trivial tower structures and partial no-hair behaviours of quantum black holes.
We study new cohomologies for the BPS operators of the N=4 Yang-Mills theory with SU(2), SU(3) and SU(4) gauge groups. The goal of this programme is to identify the black hole microstates in the dual field theory that are successfully counted by the index to match the Bekenstein-Hawking entropy. We first study the index over non-graviton cohomologies and identify their threshold levels. We present examples of the non-graviton operators in the SU(2) theory and in a subsector of the SU(3) theory that corresponds to the BMN matrix model. We also present an ansatz that can be used to construct these operators. Finally, we discuss non-trivial tower structures and partial no-hair behaviours of quantum black holes.
Posted by: IC2
Tue
21 Nov 2023
Modular factorization of superconformal indices
๐ London
Vishnu Jejjala
(Witwatersrand)
Abstract:
The Bekenstein-Hawking entropy of 1/16-BPS AdS_5 black holes is captured by a superconformal index. Such indices exhibit SL(3,Z) modular properties, which are explicated in terms of ambiguities in the Heegaard splitting of an associated Hopf surface. We conjecture a "modular factorization" of superconformal indices of general N=1 gauge theories and provide evidence for this conjecture by studying the free chiral multiplet and SQED.
The Bekenstein-Hawking entropy of 1/16-BPS AdS_5 black holes is captured by a superconformal index. Such indices exhibit SL(3,Z) modular properties, which are explicated in terms of ambiguities in the Heegaard splitting of an associated Hopf surface. We conjecture a "modular factorization" of superconformal indices of general N=1 gauge theories and provide evidence for this conjecture by studying the free chiral multiplet and SQED.
Posted by: QMW
Mon
20 Nov 2023
Lonti: The initial (boundary) value problem in numerical general relativity
Pau Figueras
(QMUL)
Abstract:
In these series of lectures we will explore initial value problem in general relativity and how it can be solved in a computer in practical situations. We will first cover the necessary mathematical foundations, including the concepts of well-posedness and strong hyperbolicity, and then explore the current formulations of Einsteinรขโฌโขs theory of gravity that are implemented in modern numerical codes, namely generalised harmonic coordinates and the BSSN formulation. We shall see how the latter can be implemented in a toy code so as to get some hands on experience. Time permitting, we will also explore the initial boundary value problem in asymptotically anti-de Sitter spaces and how it can be solved in practice using the characteristic formulation of the Einstein equations in applications of holography.
In these series of lectures we will explore initial value problem in general relativity and how it can be solved in a computer in practical situations. We will first cover the necessary mathematical foundations, including the concepts of well-posedness and strong hyperbolicity, and then explore the current formulations of Einsteinรขโฌโขs theory of gravity that are implemented in modern numerical codes, namely generalised harmonic coordinates and the BSSN formulation. We shall see how the latter can be implemented in a toy code so as to get some hands on experience. Time permitting, we will also explore the initial boundary value problem in asymptotically anti-de Sitter spaces and how it can be solved in practice using the characteristic formulation of the Einstein equations in applications of holography.
Posted by: andrea
Thu
16 Nov 2023
London Gravity Day
Organizers Toby Wiseman - Pau Figueras
(LIMS)
Abstract:
A day for gravity
A day for gravity
Posted by: oxford
Wed
15 Nov 2023
The Statistical Interpretation of Semi-Classical Gravity
Jan de Boer
(University of Amsterdam)
Abstract:
I this talk I will describe a picture which has emerged over the past few years regarding the statistical interpretation of semiclassical gravity and how this relates to wormholes, averaging and the so-called factorization puzzle, the information paradox, and a combinatorial description of 3d gravity.
I this talk I will describe a picture which has emerged over the past few years regarding the statistical interpretation of semiclassical gravity and how this relates to wormholes, averaging and the so-called factorization puzzle, the information paradox, and a combinatorial description of 3d gravity.
Posted by: IC2
Wed
15 Nov 2023
A tensor model for chaotic CFT
Julian Sonner
(University of Geneva)
Abstract:
I will describe a novel class of statistical ensembles we developed for the description of chaotic conformal field theories. These are generalisations of the usual random-matrix type theories used in the description of quantum chaotic many-body systems, and implement the kinematical as well as dynamical constraints of the CFT bootstrap. These novel statistical models take the form of distributions over random matrices and tensors. I will take some time to characterise the individual elements in terms of so-called รขโฌลapproximate CFTsรขโฌย. Finally, I will discuss the concrete realisation of these ideas for 2D, large-c CFT and point out that the resulting tensor models (subject to reasonable constraints on the spectrum) take the form of an integral over random discrete triangularisation of 3D Euclidean manifolds, governed by the 6j symbols of Virasoro, strongly suggesting a connection to three dimensional quantum gravity.
I will describe a novel class of statistical ensembles we developed for the description of chaotic conformal field theories. These are generalisations of the usual random-matrix type theories used in the description of quantum chaotic many-body systems, and implement the kinematical as well as dynamical constraints of the CFT bootstrap. These novel statistical models take the form of distributions over random matrices and tensors. I will take some time to characterise the individual elements in terms of so-called รขโฌลapproximate CFTsรขโฌย. Finally, I will discuss the concrete realisation of these ideas for 2D, large-c CFT and point out that the resulting tensor models (subject to reasonable constraints on the spectrum) take the form of an integral over random discrete triangularisation of 3D Euclidean manifolds, governed by the 6j symbols of Virasoro, strongly suggesting a connection to three dimensional quantum gravity.
Posted by: IC2
Tue
14 Nov 2023
Essential topological entanglement
๐ London
Jackson Fliss
(Cambridge U)
Abstract:
Long range entanglement is a conceptually useful notion in the physics of quantum phases of matter. E.g. in (2+1) dimensions, ground states display area law entanglement with a potential constant correction: the "topological entanglement entropy" (TEE) which is a smoking gun of topological order. Through the lens of the IR effective field theory, described by topological quantum field theory (TQFT), we encounter the following puzzle: how does a field theory with a finite dimensional Hilbert space support a divergent area law? The simple resolution to this puzzle will also suggest an alternative perspective on topological entanglement. Utilizing the algebraic formulation of entanglement I will define a quantity I will call "essential topological entanglement." It is (i) strictly topological, (ii) positive, (iii) finite, and (iv) displays more long-range features than traditional TEE. Working with Abelian p-form BF theory as an example, I will explain general aspects of essential topological entanglement. I will elaborate on potential further applications of essential topological entanglement, as well as describe some follow-up work regarding the entanglement carried by edge-modes in BF theory.
Long range entanglement is a conceptually useful notion in the physics of quantum phases of matter. E.g. in (2+1) dimensions, ground states display area law entanglement with a potential constant correction: the "topological entanglement entropy" (TEE) which is a smoking gun of topological order. Through the lens of the IR effective field theory, described by topological quantum field theory (TQFT), we encounter the following puzzle: how does a field theory with a finite dimensional Hilbert space support a divergent area law? The simple resolution to this puzzle will also suggest an alternative perspective on topological entanglement. Utilizing the algebraic formulation of entanglement I will define a quantity I will call "essential topological entanglement." It is (i) strictly topological, (ii) positive, (iii) finite, and (iv) displays more long-range features than traditional TEE. Working with Abelian p-form BF theory as an example, I will explain general aspects of essential topological entanglement. I will elaborate on potential further applications of essential topological entanglement, as well as describe some follow-up work regarding the entanglement carried by edge-modes in BF theory.
Posted by: QMW
Tue
14 Nov 2023
Decoherence and Thermalization of SU(N) gauge theories
๐ London
Andreas Schaefer
(Regensburg)
Abstract:
Decoherence and thermalisation of isolated many-particle quantum states are studied in many different subfields of physics, including high-energy physics. One of the most interesting case are Heavy Ion Collisions which can be holographically connected to string theory in Anti-de Sitter space and for which very detailed data exists. After a general introduction I will focus on the question whether SU(N) gauge theories behave as predicted by the Eigenstate Thermalization Hypothesis (ETH). To answer this question we have performed simulations for low-dimensional SU(2) gauge theories on digital computers (arXiv: 2308.16202) which gave encouraging results. As ETH makes predictions for energy eigenstates the most natural theoretical approach to study e.g. thermalization of QCD is the numnerical simulation of Hamiltonian lattice QCD on quantum computers which, however, is not yet possible. Investigating the validity of ETH on digital computers is an early step in this direction.
Decoherence and thermalisation of isolated many-particle quantum states are studied in many different subfields of physics, including high-energy physics. One of the most interesting case are Heavy Ion Collisions which can be holographically connected to string theory in Anti-de Sitter space and for which very detailed data exists. After a general introduction I will focus on the question whether SU(N) gauge theories behave as predicted by the Eigenstate Thermalization Hypothesis (ETH). To answer this question we have performed simulations for low-dimensional SU(2) gauge theories on digital computers (arXiv: 2308.16202) which gave encouraging results. As ETH makes predictions for energy eigenstates the most natural theoretical approach to study e.g. thermalization of QCD is the numnerical simulation of Hamiltonian lattice QCD on quantum computers which, however, is not yet possible. Investigating the validity of ETH on digital computers is an early step in this direction.
Posted by: QMUL2
Tue
14 Nov 2023
Nonperturbative aspects of supersymmetric gauge theories and gauge/gravity duality from lattice simulations
๐ London
Georg Bergner
(Jena)
Abstract:
In this talk I will provide briefly summarize the status of numerical lattice simulations of supersymmetric gauge theories. As an example I will focus on low dimensional supersymmetric Yang-Mills theories in the context of gauge/gravity duality.
In this talk I will provide briefly summarize the status of numerical lattice simulations of supersymmetric gauge theories. As an example I will focus on low dimensional supersymmetric Yang-Mills theories in the context of gauge/gravity duality.
Posted by: QMUL2
Mon
13 Nov 2023
Lonti: The initial (boundary) value problem in numerical general relativity
Pau Figueras
(QMUL)
Abstract:
In these series of lectures we will explore initial value problem in general relativity and how it can be solved in a computer in practical situations. We will first cover the necessary mathematical foundations, including the concepts of well-posedness and strong hyperbolicity, and then explore the current formulations of Einsteinรขโฌโขs theory of gravity that are implemented in modern numerical codes, namely generalised harmonic coordinates and the BSSN formulation. We shall see how the latter can be implemented in a toy code so as to get some hands on experience. Time permitting, we will also explore the initial boundary value problem in asymptotically anti-de Sitter spaces and how it can be solved in practice using the characteristic formulation of the Einstein equations in applications of holography.
In these series of lectures we will explore initial value problem in general relativity and how it can be solved in a computer in practical situations. We will first cover the necessary mathematical foundations, including the concepts of well-posedness and strong hyperbolicity, and then explore the current formulations of Einsteinรขโฌโขs theory of gravity that are implemented in modern numerical codes, namely generalised harmonic coordinates and the BSSN formulation. We shall see how the latter can be implemented in a toy code so as to get some hands on experience. Time permitting, we will also explore the initial boundary value problem in asymptotically anti-de Sitter spaces and how it can be solved in practice using the characteristic formulation of the Einstein equations in applications of holography.
Posted by: andrea
Thu
9 Nov 2023
Quasinormal modes of four-dimensional Schwarzschild (anti-)de Sitter black holes
๐ London
Paolo Arnaudo
(SISSA)
Abstract:
We consider black hole linear perturbation theory in a four-dimensional Schwarzschild (anti-)de Sitter background.
We describe two methods that provide the quantization condition for the quasinormal mode frequencies of the perturbation field.
The first consists of using the Nekrasov-Shatashvili functions, or, equivalently, the classical Virasoro conformal blocks, to obtain the connection coefficients for the differential equation encoding the spectral problem. The second method is based on a perturbative expansion of the local solutions of the differential equation, that involves multiple polylogarithmic functions.
We conclude by showing how the two methods shed light on the mathematical structure of the quasinormal mode frequencies, and discussing how they can be generalized to problems in different backgrounds, emphasising their effectiveness.
We consider black hole linear perturbation theory in a four-dimensional Schwarzschild (anti-)de Sitter background.
We describe two methods that provide the quantization condition for the quasinormal mode frequencies of the perturbation field.
The first consists of using the Nekrasov-Shatashvili functions, or, equivalently, the classical Virasoro conformal blocks, to obtain the connection coefficients for the differential equation encoding the spectral problem. The second method is based on a perturbative expansion of the local solutions of the differential equation, that involves multiple polylogarithmic functions.
We conclude by showing how the two methods shed light on the mathematical structure of the quasinormal mode frequencies, and discussing how they can be generalized to problems in different backgrounds, emphasising their effectiveness.
Posted by: QMW
Wed
8 Nov 2023
BPS Ensembles
Yoav Zigdon
(University of Cambridge)
Abstract:
We study ensembles of half-BPS bound states of fundamental strings and NS-fivebranes (NS5-F1 states) in the decoupling limit. We revisit a solution corresponding to an ensemble average of these bound states, and find that the appropriate duality frame for describing the near-source structure is the T-dual NS5-P frame in which the fivebranes are generically well-separated; this property results in the applicability of perturbative string theory.
The geometry sourced by the typical microstate is not close to that of the black hole that carries the same charges. When members of the ensemble spin with two fixed angular potentials about two orthogonal planes, we find that the ensemble average geometry has an ellipsoidal structure. This contrasts with ring structures obtained when fixing the angular momenta instead of the angular potentials; we trace this difference of ensembles to large fluctuations of the angular momentum in the ensemble of fixed angular potential.
We study ensembles of half-BPS bound states of fundamental strings and NS-fivebranes (NS5-F1 states) in the decoupling limit. We revisit a solution corresponding to an ensemble average of these bound states, and find that the appropriate duality frame for describing the near-source structure is the T-dual NS5-P frame in which the fivebranes are generically well-separated; this property results in the applicability of perturbative string theory.
The geometry sourced by the typical microstate is not close to that of the black hole that carries the same charges. When members of the ensemble spin with two fixed angular potentials about two orthogonal planes, we find that the ensemble average geometry has an ellipsoidal structure. This contrasts with ring structures obtained when fixing the angular momenta instead of the angular potentials; we trace this difference of ensembles to large fluctuations of the angular momentum in the ensemble of fixed angular potential.
Posted by: IC2
Wed
8 Nov 2023
Initial Boundary Value Problem For Vacuum Einstein Equations
๐ London
Zhongshan An
(U. Michigan)
Abstract:
**Send email to jeremy.mann@kcl.ac.uk for link to online seminar.** In general relativity, spacetime metrics satisfy the Einstein equations, which are wave equations in the harmonic gauge. The Cauchy problem for the vacuum Einstein equations has been well-understood since the work of Choquet-Bruhat. For an initial data set satisfying the vacuum constraint equations, there exists a solution to the vacuum Einstein equations and it is geometrically unique in the domain of dependence of the initial surface. On contrast, the initial boundary value problem (IBVP) has been much less understood. To solve for an vacuum metric in a region with time-like boundary, one needs to impose boundary conditions to guarantee geometric uniqueness of the solution. However, due to gauge issues occurring on the boundary, there has not been a satisfying choice of boundary conditions. In this talk I will discuss obstacles in establishing a well-defined IBVP for vacuum Einstein equations and the geometric uniqueness problem. Then I will talk about an existence and geometric uniqueness result in a joint work with Michael Anderson.
**Send email to jeremy.mann@kcl.ac.uk for link to online seminar.** In general relativity, spacetime metrics satisfy the Einstein equations, which are wave equations in the harmonic gauge. The Cauchy problem for the vacuum Einstein equations has been well-understood since the work of Choquet-Bruhat. For an initial data set satisfying the vacuum constraint equations, there exists a solution to the vacuum Einstein equations and it is geometrically unique in the domain of dependence of the initial surface. On contrast, the initial boundary value problem (IBVP) has been much less understood. To solve for an vacuum metric in a region with time-like boundary, one needs to impose boundary conditions to guarantee geometric uniqueness of the solution. However, due to gauge issues occurring on the boundary, there has not been a satisfying choice of boundary conditions. In this talk I will discuss obstacles in establishing a well-defined IBVP for vacuum Einstein equations and the geometric uniqueness problem. Then I will talk about an existence and geometric uniqueness result in a joint work with Michael Anderson.
Posted by: andrea
Tue
7 Nov 2023
Tambara Yamagami fusion 2-categories and fiber 2-functors
๐ London
Matthew Yu
(Oxford U)
Abstract:
Tambara-Yamagami (TY) 1-categories provide the mathematical framework to describe the algebra of extended operators of (1+1)-d theories that admit a duality defect. In this talk I will define what is the generalization of TY 1-categories for fusion 2-categories, and how to construct them from fusion 2-categories that are group-theoretical. I will also explain that group-theoretical fusion 2-categories are completely characterized by the property that the braided fusion 1-category of endomorphisms of the monoidal unit is Tannakian. Using this characterization, I will show when a fusion 2-category admits a fiber 2-functor.
Tambara-Yamagami (TY) 1-categories provide the mathematical framework to describe the algebra of extended operators of (1+1)-d theories that admit a duality defect. In this talk I will define what is the generalization of TY 1-categories for fusion 2-categories, and how to construct them from fusion 2-categories that are group-theoretical. I will also explain that group-theoretical fusion 2-categories are completely characterized by the property that the braided fusion 1-category of endomorphisms of the monoidal unit is Tannakian. Using this characterization, I will show when a fusion 2-category admits a fiber 2-functor.
Posted by: QMW
Mon
6 Nov 2023
Lonti: The initial (boundary) value problem in numerical general relativity
Pau Figueras
(QMUL)
Abstract:
In these series of lectures we will explore initial value problem in general relativity and how it can be solved in a computer in practical situations. We will first cover the necessary mathematical foundations, including the concepts of well-posedness and strong hyperbolicity, and then explore the current formulations of Einsteinรขโฌโขs theory of gravity that are implemented in modern numerical codes, namely generalised harmonic coordinates and the BSSN formulation. We shall see how the latter can be implemented in a toy code so as to get some hands on experience. Time permitting, we will also explore the initial boundary value problem in asymptotically anti-de Sitter spaces and how it can be solved in practice using the characteristic formulation of the Einstein equations in applications of holography.
In these series of lectures we will explore initial value problem in general relativity and how it can be solved in a computer in practical situations. We will first cover the necessary mathematical foundations, including the concepts of well-posedness and strong hyperbolicity, and then explore the current formulations of Einsteinรขโฌโขs theory of gravity that are implemented in modern numerical codes, namely generalised harmonic coordinates and the BSSN formulation. We shall see how the latter can be implemented in a toy code so as to get some hands on experience. Time permitting, we will also explore the initial boundary value problem in asymptotically anti-de Sitter spaces and how it can be solved in practice using the characteristic formulation of the Einstein equations in applications of holography.
Posted by: andrea
Mon
6 Nov 2023
New perspectives on Turbulence
Alexander Migdal
(NYU)
Thu
2 Nov 2023
Intelligent Explorations of the String Landscape
๐ London
Thomas Harvey
(Oxford U.)
Abstract:
String theory has far surpassed expectations in its ability to shed light on many areas of theoretical and mathematical physics. However, partly due to the immense size of the solution space, it is yet to be determined if our universe lives somewhere in the string landscape. In this talk, I will present how methods from computer science (genetic algorithms and reinforcement learning) can shed some light on these questions by exploring promising regions of the string landscape. Specifically, reinforcement learning and genetic algorithms are used to construct sums of line bundles and monad bundles on smooth Calabi-Yau threefolds, for compactifications of E8xE8 heterotic string theory.
String theory has far surpassed expectations in its ability to shed light on many areas of theoretical and mathematical physics. However, partly due to the immense size of the solution space, it is yet to be determined if our universe lives somewhere in the string landscape. In this talk, I will present how methods from computer science (genetic algorithms and reinforcement learning) can shed some light on these questions by exploring promising regions of the string landscape. Specifically, reinforcement learning and genetic algorithms are used to construct sums of line bundles and monad bundles on smooth Calabi-Yau threefolds, for compactifications of E8xE8 heterotic string theory.
Posted by: QMW
Wed
1 Nov 2023
t Hooft loops and integrability
๐ London
Kostantin Zarembo
(Nordita)
Abstract:
A รขโฌโขt Hooft loop is a typical disorder operator defined in any gauge theory that can be studied by a combination of holography, localization and integrability. After reviewing the quantum mechanics magnetic monopoles, I will describe how integrability and Bethe ansatz can help to study รขโฌโขt Hooft loops in the N=4 super-Yang-Mills theory.
A รขโฌโขt Hooft loop is a typical disorder operator defined in any gauge theory that can be studied by a combination of holography, localization and integrability. After reviewing the quantum mechanics magnetic monopoles, I will describe how integrability and Bethe ansatz can help to study รขโฌโขt Hooft loops in the N=4 super-Yang-Mills theory.
Posted by: andrea
Wed
1 Nov 2023
5d SCFTs and their non-supersymmetric cousins
Mohammad Akhond
(Kyoto University)
Abstract:
I will argue that combining old ideas such as dualities and exact results in SUSY QFTs supplemented with recent techniques such as SPT phases and generalised anomalies can shed light on strong coupling dynamics of non-SUSY theories. I will in particular show that non-SUSY gauge theories, which are related to SUSY SCFTs by RG in 5d exhibit phase transitions in the UV which are candidates for non-SUSY fixed points.
I will argue that combining old ideas such as dualities and exact results in SUSY QFTs supplemented with recent techniques such as SPT phases and generalised anomalies can shed light on strong coupling dynamics of non-SUSY theories. I will in particular show that non-SUSY gauge theories, which are related to SUSY SCFTs by RG in 5d exhibit phase transitions in the UV which are candidates for non-SUSY fixed points.
Posted by: IC2
October 2023
Tue
31 Oct 2023
Double copy from momentum space to coordinate and Twistors space
Mariana Carrillo Gonzalez
(Imperial College London)
Abstract:
In this talk I will introduce the double copy construction that allows us to write gravitational scattering amplitudes as the "square" of gauge theory ones. I will show how the standard construction can be generalized to include massive mediators and how this relationship can also be observed for classical solutions in coordinate space as well as for cohomology class representatives in twistor space. Throughout the talk I will focus on the example of Topologically Massive Theories.
In this talk I will introduce the double copy construction that allows us to write gravitational scattering amplitudes as the "square" of gauge theory ones. I will show how the standard construction can be generalized to include massive mediators and how this relationship can also be observed for classical solutions in coordinate space as well as for cohomology class representatives in twistor space. Throughout the talk I will focus on the example of Topologically Massive Theories.
Posted by: IC2
Thu
26 Oct 2023
Decomposition of 2d pure Yang-Mills and the Gross-Taylor string theory
๐ London
Eric Sharpe
(Virginia Tech.)
Abstract:
In this talk we will attempt to reconcile two different results on
two-dimensional pure Yang-Mills theory.
Specifically, we will discuss how the fact that 2d pure Yang-Mills is equivalent
to a disjoint union of theories, is related to the Gross-Taylor description
of 2d pure Yang-Mills as the target-space field theory of a string theory.
The Gross-Taylor picture can be understood by first rewriting the
Yang-Mills partition function (in a large N limit) as a sum of
correlation functions in Dijkgraaf-Witten theories for the symmetric group
S_n, and then interpreting those Dijkgraaf-Witten
correlation functions in terms of
branched covers, which leads to the string theory description.
We first observe that the decomposition of the pure Yang-Mills aligns
perfectly with decomposition of S_n Dijkgraaf-Witten theory, and then
discuss decomposition and the branched covers interpretation.
We encounter two puzzles, and to solve them, propose that the Gross-Taylor
string theory has a higher-form symmetry.
In this talk we will attempt to reconcile two different results on
two-dimensional pure Yang-Mills theory.
Specifically, we will discuss how the fact that 2d pure Yang-Mills is equivalent
to a disjoint union of theories, is related to the Gross-Taylor description
of 2d pure Yang-Mills as the target-space field theory of a string theory.
The Gross-Taylor picture can be understood by first rewriting the
Yang-Mills partition function (in a large N limit) as a sum of
correlation functions in Dijkgraaf-Witten theories for the symmetric group
S_n, and then interpreting those Dijkgraaf-Witten
correlation functions in terms of
branched covers, which leads to the string theory description.
We first observe that the decomposition of the pure Yang-Mills aligns
perfectly with decomposition of S_n Dijkgraaf-Witten theory, and then
discuss decomposition and the branched covers interpretation.
We encounter two puzzles, and to solve them, propose that the Gross-Taylor
string theory has a higher-form symmetry.
Posted by: QMW
Wed
25 Oct 2023
Integrable Quantum Field Theories Perturbed by Irrelevant Operators
Olalla Castro Alvaredo
(City University of London)
Abstract:
In this talk I will review recent results co-authored with Stefano Negro, Fabio Sailis and Istvรยกn Szรยฉcsรยฉnyi. In this project we have addressed the problem of how to compute correlation functions in integrable quantum field theories perturbed by irrelevant perturbations such as the operator TTbar. It has been known for some time that integrability is preserved under such perturbations even though the S-matrix is modified by a CDD factor. Therefore, it is natural to expect that matrix elements of local fields may be computed by employing the standard form factor program, which was developed for integrable quantum field theories in the 70s. By doing so we have found that the form factors of local and semi-local fields have a universal structure which we have identified. This gives rise to correlation functions with distinct convergence/divergence properties, depending on the sign of the perturbation. In the convergent regime we find that the correlation functions scale as power-laws at short distances, similar to standard integrable quantum field theories, but with powers that are no longer the conformal dimensions of some field. At the heart of our construction is a function called the minimal form factor, whose structure I will discuss in some detail.
In this talk I will review recent results co-authored with Stefano Negro, Fabio Sailis and Istvรยกn Szรยฉcsรยฉnyi. In this project we have addressed the problem of how to compute correlation functions in integrable quantum field theories perturbed by irrelevant perturbations such as the operator TTbar. It has been known for some time that integrability is preserved under such perturbations even though the S-matrix is modified by a CDD factor. Therefore, it is natural to expect that matrix elements of local fields may be computed by employing the standard form factor program, which was developed for integrable quantum field theories in the 70s. By doing so we have found that the form factors of local and semi-local fields have a universal structure which we have identified. This gives rise to correlation functions with distinct convergence/divergence properties, depending on the sign of the perturbation. In the convergent regime we find that the correlation functions scale as power-laws at short distances, similar to standard integrable quantum field theories, but with powers that are no longer the conformal dimensions of some field. At the heart of our construction is a function called the minimal form factor, whose structure I will discuss in some detail.
Posted by: IC2
Tue
24 Oct 2023
From amplitudes to black hole encounters
๐ London
Rodolfo Russo and Carlo Heissenberg
(QMUL)
Abstract:
We will discuss how amplitudes can be used to efficiently derive classical
gravitational-wave observables characterizing black hole binary encounters.
This technique is very flexible and can be applied to General Relativity, but
also to its extensions and, in the spirit of Effective Field Theory, can be used
to describe compact objects beyond Schwarzschild black holes. We will briefly
discuss some recent applications to spinning black holes and to the subleading
Post-Minkowsian waveforms.
We will discuss how amplitudes can be used to efficiently derive classical
gravitational-wave observables characterizing black hole binary encounters.
This technique is very flexible and can be applied to General Relativity, but
also to its extensions and, in the spirit of Effective Field Theory, can be used
to describe compact objects beyond Schwarzschild black holes. We will briefly
discuss some recent applications to spinning black holes and to the subleading
Post-Minkowsian waveforms.
Posted by: QMUL2
Mon
23 Oct 2023
Lonti: Supergravity a la Fin de Siecle
Neil Lambert
(KCL)
Abstract:
In these lectures we will provide a basic introduction to Supergravity as it arises in String Theory and M-Theory. We will start by introducing vielbeins and spin connections in order to construct supergravity actions. In the second lecture we will briefly introduce the maximal supergravity theories in ten and eleven-dimensions. We will briefly discuss special holonomy manifolds, explicitly construct BPS p-brane solutions and prove their non-perturbative stability. Time permitting we will discuss toroidal compactifications and U-duality.
I will assume basic MSc level material (Riemannian geometry, fermions and rigid supersymmetry). The lecture notes that will be provided are largely self-contained but the text book รขโฌลSupergravityรขโฌย by Freedman and van Proeyen contains more details.
This time, there will be two lectures (one in the morning and one in the afternoon), with pizza lunch in between them.
In these lectures we will provide a basic introduction to Supergravity as it arises in String Theory and M-Theory. We will start by introducing vielbeins and spin connections in order to construct supergravity actions. In the second lecture we will briefly introduce the maximal supergravity theories in ten and eleven-dimensions. We will briefly discuss special holonomy manifolds, explicitly construct BPS p-brane solutions and prove their non-perturbative stability. Time permitting we will discuss toroidal compactifications and U-duality.
I will assume basic MSc level material (Riemannian geometry, fermions and rigid supersymmetry). The lecture notes that will be provided are largely self-contained but the text book รขโฌลSupergravityรขโฌย by Freedman and van Proeyen contains more details.
This time, there will be two lectures (one in the morning and one in the afternoon), with pizza lunch in between them.
Posted by: andrea
Wed
18 Oct 2023
Lessons from Defects in the N=4 Super-Yang-Mills
Yifan Wang
(NYU)
Abstract:
I'll discuss recent results on line and surface defects in the N=4 Super-Yang-Mills (SYM) beyond perturbation theory. In addition to providing new observables in the SYM that capture the gauge theory dynamics in the presence of impurities, these non-perturbative results detect the nontrivial SL(2,Z) structure and provide an exact order parameter for the deconfinement phase transition. Furthermore, via AdS/CFT, they lead to novel predictions for the world-volume action of branes in type IIB string theory at finite string coupling and present a new perspective on the Hawking-Page transition for black holes in AdS.
I'll discuss recent results on line and surface defects in the N=4 Super-Yang-Mills (SYM) beyond perturbation theory. In addition to providing new observables in the SYM that capture the gauge theory dynamics in the presence of impurities, these non-perturbative results detect the nontrivial SL(2,Z) structure and provide an exact order parameter for the deconfinement phase transition. Furthermore, via AdS/CFT, they lead to novel predictions for the world-volume action of branes in type IIB string theory at finite string coupling and present a new perspective on the Hawking-Page transition for black holes in AdS.
Posted by: CityU2
Wed
18 Oct 2023
The Hagedorn temperature in planar N = 4 super Yang-Mills, ABJM, and string theory
Joseph Minahan
(Uppsala)
Abstract:
We discuss numerical results from integrability for the Hagedorn temperature in N=4 SYM and ABJM theory at strong coupling and compare them to the Hagedorn temperatures of their string theory duals. From the numerics we conjecture the leading analytic coefficients in the expansion about large 't Hooft coupling. This talk is based on arXiv:2306.09883 and arXiv:2307.02350.
We discuss numerical results from integrability for the Hagedorn temperature in N=4 SYM and ABJM theory at strong coupling and compare them to the Hagedorn temperatures of their string theory duals. From the numerics we conjecture the leading analytic coefficients in the expansion about large 't Hooft coupling. This talk is based on arXiv:2306.09883 and arXiv:2307.02350.
Posted by: CityU2
Tue
17 Oct 2023
Z_N duality and parafermions revisited
๐ London
Zhihao Duan
(QMUL)
Abstract:
The Symmetry Topological field theory (SymTFT) has played an important role in recent studies of symmetries in physics. As one application, it provides a clear and unifying picture of bosonization and fermionization in two dimensions. On the other hand, for theories having a non-anomalous Z_N symmetry with N > 2, people have long speculated about the presence of parafermions. In this informal talk, we revisit the bosonization/parafermionization procedure from the SymTFT point of view, and explain some subtleties and peculiarities involved. It will be based on 2309.01913 and (hopefully) accessible to a broad audience. Part of the London TQFT journal club (https://www.london-tqft.co.uk)
The Symmetry Topological field theory (SymTFT) has played an important role in recent studies of symmetries in physics. As one application, it provides a clear and unifying picture of bosonization and fermionization in two dimensions. On the other hand, for theories having a non-anomalous Z_N symmetry with N > 2, people have long speculated about the presence of parafermions. In this informal talk, we revisit the bosonization/parafermionization procedure from the SymTFT point of view, and explain some subtleties and peculiarities involved. It will be based on 2309.01913 and (hopefully) accessible to a broad audience. Part of the London TQFT journal club (https://www.london-tqft.co.uk)
Posted by: QMW
Mon
16 Oct 2023
Lonti: Supergravity a la Fin de Siecle
Neil Lambert
(KCL)
Abstract:
In these lectures we will provide a basic introduction to Supergravity as it arises in String Theory and M-Theory. We will start by introducing vielbeins and spin connections in order to construct supergravity actions. In the second lecture we will briefly introduce the maximal supergravity theories in ten and eleven-dimensions. We will briefly discuss special holonomy manifolds, explicitly construct BPS p-brane solutions and prove their non-perturbative stability. Time permitting we will discuss toroidal compactifications and U-duality.
I will assume basic MSc level material (Riemannian geometry, fermions and rigid supersymmetry). The lecture notes that will be provided are largely self-contained but the text book รขโฌลSupergravityรขโฌย by Freedman and van Proeyen contains more details.
In these lectures we will provide a basic introduction to Supergravity as it arises in String Theory and M-Theory. We will start by introducing vielbeins and spin connections in order to construct supergravity actions. In the second lecture we will briefly introduce the maximal supergravity theories in ten and eleven-dimensions. We will briefly discuss special holonomy manifolds, explicitly construct BPS p-brane solutions and prove their non-perturbative stability. Time permitting we will discuss toroidal compactifications and U-duality.
I will assume basic MSc level material (Riemannian geometry, fermions and rigid supersymmetry). The lecture notes that will be provided are largely self-contained but the text book รขโฌลSupergravityรขโฌย by Freedman and van Proeyen contains more details.
Posted by: andrea
Mon
16 Oct 2023
Entanglement in Internal spaces
Sumit Das
(University of Kentucky)
Abstract:
We discuss two notions of entanglement of internal degrees of freedom. The first notion is target
space entanglement: we show how to define entanglement of matrix degrees of freedom in a gauge
invariant manner, and discuss connections to holography. The second notion relates to global symmetries in
AdS/CFT settings and relates to an interpretation of Ryu-Takayanagi surfaces which are anchored on the boundary of
a subregion on the internal space and smeared in the AdS spatial directions.
We discuss two notions of entanglement of internal degrees of freedom. The first notion is target
space entanglement: we show how to define entanglement of matrix degrees of freedom in a gauge
invariant manner, and discuss connections to holography. The second notion relates to global symmetries in
AdS/CFT settings and relates to an interpretation of Ryu-Takayanagi surfaces which are anchored on the boundary of
a subregion on the internal space and smeared in the AdS spatial directions.
Posted by: IC2
Thu
12 Oct 2023
Torus 1-point functions for the su2 WZW model and their modular properties
๐ London
Simon Wood
(Cardiff U.)
Abstract:
Characters of representations of chiral algebras are important tools in conformal field theory. They are a special chase of chiral torus 1-point functions (namely those where the vacuum has been inserted) and their modular properties famously give rise to the Verlinde formula. In this talk we will generalise from vacuum insertions to insertions from any irreducible representation in the example of the su2 WZW models at non-negative integral level and explore their modular properties.
Characters of representations of chiral algebras are important tools in conformal field theory. They are a special chase of chiral torus 1-point functions (namely those where the vacuum has been inserted) and their modular properties famously give rise to the Verlinde formula. In this talk we will generalise from vacuum insertions to insertions from any irreducible representation in the example of the su2 WZW models at non-negative integral level and explore their modular properties.
Posted by: QMW
Wed
11 Oct 2023
QFT in AdS instead of LSZ
๐ London
Balt van Rees
(Ecole Polytechnique)
Abstract:
The boundary correlation functions for a quantum field theory (QFT) in a fixed antiรขโฌโde Sitter (AdS) background should reduce to S-matrix elements in the flat-space limit. We consider this procedure in detail for four-point functions. With minimal assumptions we rigorously show that the resulting S-matrix element obeys a dispersion relation, the nonlinear unitarity conditions, and the Froissart-Martin bound. QFT in AdS thus provides an alternative route to fundamental QFT results that normally rely on the LSZ axioms.
The boundary correlation functions for a quantum field theory (QFT) in a fixed antiรขโฌโde Sitter (AdS) background should reduce to S-matrix elements in the flat-space limit. We consider this procedure in detail for four-point functions. With minimal assumptions we rigorously show that the resulting S-matrix element obeys a dispersion relation, the nonlinear unitarity conditions, and the Froissart-Martin bound. QFT in AdS thus provides an alternative route to fundamental QFT results that normally rely on the LSZ axioms.
Posted by: andrea
Wed
11 Oct 2023
Analytic bootstrap for magnetic impurities
Lorenzo Bianchi
(University of Torino)
Abstract:
We will discuss two classes of line defects in the O(N) critical model at the Wilson-Fisher fixed point. These extended excitations are relevant for condensed matter systems, such as doped quantum antiferromagnets. After reviewing some state-of-the-art analytic bootstrap techniques, we will apply them to compute the correlator of two bulk excitations at first order in the epsilon expansion. From this result we are able to extract an infinite set of defect CFT data.
We will discuss two classes of line defects in the O(N) critical model at the Wilson-Fisher fixed point. These extended excitations are relevant for condensed matter systems, such as doped quantum antiferromagnets. After reviewing some state-of-the-art analytic bootstrap techniques, we will apply them to compute the correlator of two bulk excitations at first order in the epsilon expansion. From this result we are able to extract an infinite set of defect CFT data.
Posted by: IC2
Tue
10 Oct 2023
Black hole from matrices for dummies
๐ London
Masanori Hanada
(QMUL)
Abstract:
We will give an intuitive explanation of why and how matrices (or, more precisely, large-N gauge theories) can describe a black hole, without assuming knowledge of quantum mechanics and holographic duality.
Firstly, we explain an intuitive picture inroduced by Witten: diagonal entries of matrices describe particles and off-diagonal entries describe strings connecting particles. When many strings are excited, a lot of energy and entropy are packed in a small region and form black hole.
Next, we consider classical dynamics of matrix model. Specifically, we colide two black holes. Using the energy conservation, equipartition law of energy and elementary school math, we show that black hole becomes colder after the merger. Matrices know black hole's negative heat capacity!
To gain a little bit more intuition, we will look at ants. Collective behavior of ants has a striking similarity to black hole. The mapping rule is ant -> particle, pheromone -> string, and ant trail -> black hole. Tuning parameters such as temperature or each ant's laziness, we can obtain three kinds of phase diagrams. Each of them has a counterpart in large-N gauge theories.
If time permits, I will explain the mechanism applicable to strongly-coupled and highly quantum regime needed for quantitative agreement with Einstein gravity. (This part requires a good understanding of undergraduate-level quantum mechanics.)
We will give an intuitive explanation of why and how matrices (or, more precisely, large-N gauge theories) can describe a black hole, without assuming knowledge of quantum mechanics and holographic duality.
Firstly, we explain an intuitive picture inroduced by Witten: diagonal entries of matrices describe particles and off-diagonal entries describe strings connecting particles. When many strings are excited, a lot of energy and entropy are packed in a small region and form black hole.
Next, we consider classical dynamics of matrix model. Specifically, we colide two black holes. Using the energy conservation, equipartition law of energy and elementary school math, we show that black hole becomes colder after the merger. Matrices know black hole's negative heat capacity!
To gain a little bit more intuition, we will look at ants. Collective behavior of ants has a striking similarity to black hole. The mapping rule is ant -> particle, pheromone -> string, and ant trail -> black hole. Tuning parameters such as temperature or each ant's laziness, we can obtain three kinds of phase diagrams. Each of them has a counterpart in large-N gauge theories.
If time permits, I will explain the mechanism applicable to strongly-coupled and highly quantum regime needed for quantitative agreement with Einstein gravity. (This part requires a good understanding of undergraduate-level quantum mechanics.)
Posted by: QMUL2
Tue
10 Oct 2023
Progress in strong field scattering
Tim Adamo
(University of Edinburgh)
Abstract:
Scattering amplitudes in strong background fields provide an arena where perturbative and non-perturbative physics meet, with important applications ranging from laser physics to black holes, but their study is hampered by the cumbersome nature of QFT in the background field formalism. In this talk, I will try to convince you that strong-field scattering amplitudes contain a wealth of physical information which cannot be obtained with standard perturbative techniques, ranging from all-order classical observables to constraints on exact solutions. Furthermore, I will discuss how in chiral strong fields, remarkable progress is possible using methods based on twistor theory.
Scattering amplitudes in strong background fields provide an arena where perturbative and non-perturbative physics meet, with important applications ranging from laser physics to black holes, but their study is hampered by the cumbersome nature of QFT in the background field formalism. In this talk, I will try to convince you that strong-field scattering amplitudes contain a wealth of physical information which cannot be obtained with standard perturbative techniques, ranging from all-order classical observables to constraints on exact solutions. Furthermore, I will discuss how in chiral strong fields, remarkable progress is possible using methods based on twistor theory.
Posted by: IC2
Mon
9 Oct 2023
LonTI lectures: Supergravity a la Fin de Siecle
Neil Lambert
(KCL)
Abstract:
In these lectures we will provide a basic introduction to Supergravity as it arises in String Theory and M-Theory. We will start by introducing vielbeins and spin connections in order to construct supergravity actions. In the second lecture we will briefly introduce the maximal supergravity theories in ten and eleven-dimensions. We will briefly discuss special holonomy manifolds, explicitly construct BPS p-brane solutions and prove their non-perturbative stability. Time permitting we will discuss toroidal compactifications and U-duality.
I will assume basic MSc level material (Riemannian geometry, fermions and rigid supersymmetry). The lecture notes that will be provided are largely self-contained but the text book รขโฌลSupergravityรขโฌย by Freedman and van Proeyen contains more details.
In these lectures we will provide a basic introduction to Supergravity as it arises in String Theory and M-Theory. We will start by introducing vielbeins and spin connections in order to construct supergravity actions. In the second lecture we will briefly introduce the maximal supergravity theories in ten and eleven-dimensions. We will briefly discuss special holonomy manifolds, explicitly construct BPS p-brane solutions and prove their non-perturbative stability. Time permitting we will discuss toroidal compactifications and U-duality.
I will assume basic MSc level material (Riemannian geometry, fermions and rigid supersymmetry). The lecture notes that will be provided are largely self-contained but the text book รขโฌลSupergravityรขโฌย by Freedman and van Proeyen contains more details.
Posted by: andrea
Mon
9 Oct 2023
Tensors models for 3d gravity
Daniel Jafferis
(Harvard University)
Thu
5 Oct 2023
Amplitudes in the sky
๐ London
Scott Melville
(Queen Mary U. of London)
Abstract:
I will describe some recent developments in applying amplitude and effective field theory ideas in cosmology, and focus in particular on what cosmological measurements (of e.g. the cosmic microwave background or large-scale structure of galaxies) can tell us about the underlying fundamental field theory.
I will describe some recent developments in applying amplitude and effective field theory ideas in cosmology, and focus in particular on what cosmological measurements (of e.g. the cosmic microwave background or large-scale structure of galaxies) can tell us about the underlying fundamental field theory.
Posted by: QMW
Wed
4 Oct 2023
Renormalization group flows in AdS and the bootstrap program
๐ London
Marco Meineri
(U. Turin)
Abstract:
We consider the renormalization group flow of a quantum field theory (QFT) in Anti-de Sitter (AdS) space. We derive sum rules that express UV data and the energy of a chosen eigenstate in terms of the spectral densities and certain correlation functions of the theory. In two dimensions, this leads to a bootstrap setup that involves the UV central charge and may allow us to follow a Renormalization Group (RG) flow non-perturbatively by continuously varying the AdS radius. Along the way, we establish the convergence properties of the newly discovered local block decomposition, which applies to three-point functions involving one bulk and two boundary operators.
We consider the renormalization group flow of a quantum field theory (QFT) in Anti-de Sitter (AdS) space. We derive sum rules that express UV data and the energy of a chosen eigenstate in terms of the spectral densities and certain correlation functions of the theory. In two dimensions, this leads to a bootstrap setup that involves the UV central charge and may allow us to follow a Renormalization Group (RG) flow non-perturbatively by continuously varying the AdS radius. Along the way, we establish the convergence properties of the newly discovered local block decomposition, which applies to three-point functions involving one bulk and two boundary operators.
Posted by: andrea
Wed
4 Oct 2023
Wheeler DeWitt States of a Charged AdS4 Black Hole
Sirui Ning
(University of Oxford)
Abstract:
In this talk, I will present a thorough investigation of the Wheeler-de Witt(WdW) equation within the framework of a Reissner-Nordstrom Anti-de Sitter (RN-AdS) black hole background and its relation to holographic renormalization flow. We solve the Wheeler DeWitt equation for the planar Reissner-Nordstrom-AdS black hole in a minisuperspace approximation and construct semiclassical Wheeler DeWitt states from Gaussian wavepackets that are peaked on classical black hole interior solutions. Furthermore, towards the AdS boundary, the Wheeler DeWitt states are used to recover the Lorentzian partition function of the dual theory living on this boundary. This partition function is specified by an energy and a charge. Finally, we show that the Wheeler DeWitt states know about the black hole thermodynamics, recovering the grand canonical thermodynamic potential after an appropriate averaging at the black hole horizon.
In this talk, I will present a thorough investigation of the Wheeler-de Witt(WdW) equation within the framework of a Reissner-Nordstrom Anti-de Sitter (RN-AdS) black hole background and its relation to holographic renormalization flow. We solve the Wheeler DeWitt equation for the planar Reissner-Nordstrom-AdS black hole in a minisuperspace approximation and construct semiclassical Wheeler DeWitt states from Gaussian wavepackets that are peaked on classical black hole interior solutions. Furthermore, towards the AdS boundary, the Wheeler DeWitt states are used to recover the Lorentzian partition function of the dual theory living on this boundary. This partition function is specified by an energy and a charge. Finally, we show that the Wheeler DeWitt states know about the black hole thermodynamics, recovering the grand canonical thermodynamic potential after an appropriate averaging at the black hole horizon.
Posted by: IC2
Tue
3 Oct 2023
Renormalization group flows in AdS and the bootstrap program
๐ London
Marco Meineri
(Turin U.)
Abstract:
We consider the renormalization group flow of a quantum field theory (QFT) in Anti-de Sitter (AdS) space. We derive sum rules that express UV data and the energy of a chosen eigenstate in terms of the spectral densities and certain correlation functions of the theory. In two dimensions, this leads to a bootstrap setup that involves the UV central charge and may allow us to follow a Renormalization Group (RG) flow non-perturbatively by continuously varying the AdS radius. Along the way, we establish the convergence properties of the newly discovered local block decomposition, which applies to three-point functions involving one bulk and two boundary operators.
We consider the renormalization group flow of a quantum field theory (QFT) in Anti-de Sitter (AdS) space. We derive sum rules that express UV data and the energy of a chosen eigenstate in terms of the spectral densities and certain correlation functions of the theory. In two dimensions, this leads to a bootstrap setup that involves the UV central charge and may allow us to follow a Renormalization Group (RG) flow non-perturbatively by continuously varying the AdS radius. Along the way, we establish the convergence properties of the newly discovered local block decomposition, which applies to three-point functions involving one bulk and two boundary operators.
Posted by: QMW
Tue
3 Oct 2023
Understanding the AdS3/CFT2 correspondence with integrability
Alessandro Sfondrini
(University of Padova)
Abstract:
The AdS3/CFT2 correspondence is the conjecture that gravity (more specifically superstrings) should be dual to some two-dimensional conformal field theory. Currently, the precise form of this CFT, or its features, are largely unknown. In this blackboard talk, I will review what is know, what is not, and how we are slowly but steadily making progress thanks to techniques from the world of integrable models.
The AdS3/CFT2 correspondence is the conjecture that gravity (more specifically superstrings) should be dual to some two-dimensional conformal field theory. Currently, the precise form of this CFT, or its features, are largely unknown. In this blackboard talk, I will review what is know, what is not, and how we are slowly but steadily making progress thanks to techniques from the world of integrable models.
Posted by: IC2
September 2023
Thu
28 Sep 2023
Kerr Amplitudes from Higher Spin Theory
๐ London
Lucile Cangemi
(Uppsala University)
Abstract:
Higher-spin theory and massive gauge invariance can be used as input for constraining root-Kerr and Kerr amplitudes, relevant for calculating gravitational observables with spin. Elegant three-point spin-s amplitudes exist for Kerr black holes, however constructing the corresponding four-point Compton amplitudes is an open problem. In this talk, I will discuss the origin of the Kerr three-point amplitudes from a higher-spin theory perspective. Guided by higher-spin constraints and classical-limit analysis, I will propose quantum and classical tree-level Compton amplitudes relevant for root-Kerr and Kerr to all orders in spin.
Higher-spin theory and massive gauge invariance can be used as input for constraining root-Kerr and Kerr amplitudes, relevant for calculating gravitational observables with spin. Elegant three-point spin-s amplitudes exist for Kerr black holes, however constructing the corresponding four-point Compton amplitudes is an open problem. In this talk, I will discuss the origin of the Kerr three-point amplitudes from a higher-spin theory perspective. Guided by higher-spin constraints and classical-limit analysis, I will propose quantum and classical tree-level Compton amplitudes relevant for root-Kerr and Kerr to all orders in spin.
Posted by: QMW
Wed
27 Sep 2023
TBA
Kuo-Wei Huang
(University of Southampton )
Abstract:
TBA.
This is part of the first HoloUK meeting. Attendance is free but registration is needed because of space limitations. Please register at https://sites.google.com/view/holouk/home/holouk-1.
TBA.
This is part of the first HoloUK meeting. Attendance is free but registration is needed because of space limitations. Please register at https://sites.google.com/view/holouk/home/holouk-1.
Posted by: andrea
Wed
27 Sep 2023
TBA
Michal Heller
(Ghent University)
Abstract:
TBA.
This is part of the first HoloUK meeting. Attendance is free but registration is needed because of space limitations. Please register at https://sites.google.com/view/holouk/home/holouk-1.
TBA.
This is part of the first HoloUK meeting. Attendance is free but registration is needed because of space limitations. Please register at https://sites.google.com/view/holouk/home/holouk-1.
Posted by: andrea
Thu
21 Sep 2023
Bootstrability with Improved Truncation Methods
๐ London
Vasilis Niarchos
(Crete U.)
Abstract:
I will discuss recent work on the numerical conformal bootstrap that modifies the scope of the so-called truncation methods and improves their efficiency. I will show how the proposed approach performs in the recently discussed context of bootstrability for 1d defect CFTs on 1/2 BPS Wilson lines in 4d N=4 SYM theory, how it compares with the more standard linear functional method and how different algorithms allow us to tackle the large-scale non-convex optimization problems that are involved in this method. Along the way, I will address the prospects of AI and Machine Learning in this particular direction.
I will discuss recent work on the numerical conformal bootstrap that modifies the scope of the so-called truncation methods and improves their efficiency. I will show how the proposed approach performs in the recently discussed context of bootstrability for 1d defect CFTs on 1/2 BPS Wilson lines in 4d N=4 SYM theory, how it compares with the more standard linear functional method and how different algorithms allow us to tackle the large-scale non-convex optimization problems that are involved in this method. Along the way, I will address the prospects of AI and Machine Learning in this particular direction.
Posted by: QMW