Triangle Seminars
August 2020
Tue
4 Aug 2020
Gravity/Ensemble Duality
Elizabeth Wildenhain
(University of California, Berkeley)
Abstract:
For the first time, a gravitational calculation was recently shown to yield the Page curve for the entropy of Hawking radiation, consistent with unitary evolution. However, the calculation takes as essential input Hawking's result that the radiation entropy becomes large at late times. We call this apparent contradiction the state paradox. We exhibit its manifestations in standard and doubly-holographic settings, with and without an external bath. We clarify which version(s) of the Ryu-Takayanagi prescription apply in each setting. We show that the two possible homology rules in the presence of a braneworld generate a bulk dual of the state paradox. The paradox is resolved if the gravitational path integral computes averaged quantities in a suitable ensemble of unitary theories, a possibility supported independently by several recent developments. ––- Follow the usual link or contact the organisers (Antoine Bourget and Edoardo Vescovi).
For the first time, a gravitational calculation was recently shown to yield the Page curve for the entropy of Hawking radiation, consistent with unitary evolution. However, the calculation takes as essential input Hawking's result that the radiation entropy becomes large at late times. We call this apparent contradiction the state paradox. We exhibit its manifestations in standard and doubly-holographic settings, with and without an external bath. We clarify which version(s) of the Ryu-Takayanagi prescription apply in each setting. We show that the two possible homology rules in the presence of a braneworld generate a bulk dual of the state paradox. The paradox is resolved if the gravitational path integral computes averaged quantities in a suitable ensemble of unitary theories, a possibility supported independently by several recent developments. ––- Follow the usual link or contact the organisers (Antoine Bourget and Edoardo Vescovi).
Posted by: IC
July 2020
Tue
28 Jul 2020
Wormholes and branes in JT gravity
Andreas Blommaert
(Ghent University)
Abstract:
I will highlight the role of wormholes and branes in reconciling semiclassical gravitational (black hole) physics with unitary quantum mechanical evolution. Most of the talk will be based on recent developments in JT gravity. This is a model of quantum gravity in two dimensions which is analytically tractable. I will first explain why we need wormholes in order to capture late time properties of chaotic quantum systems from a geometrical point of view. I then point out that naively the inclusion of wormholes in a gravitational theory comes with an ensemble interpretation of said gravitational theory. Finally I will explain how this conclusion (that gravity is an ensemble) can be avoided by including branes in the bulk geometrical description. These branes can encode the micro structure of a given unitary quantum system in bulk geometry. ––- Follow the usual link or contact the organisers (Antoine Bourget and Edoardo Vescovi).
I will highlight the role of wormholes and branes in reconciling semiclassical gravitational (black hole) physics with unitary quantum mechanical evolution. Most of the talk will be based on recent developments in JT gravity. This is a model of quantum gravity in two dimensions which is analytically tractable. I will first explain why we need wormholes in order to capture late time properties of chaotic quantum systems from a geometrical point of view. I then point out that naively the inclusion of wormholes in a gravitational theory comes with an ensemble interpretation of said gravitational theory. Finally I will explain how this conclusion (that gravity is an ensemble) can be avoided by including branes in the bulk geometrical description. These branes can encode the micro structure of a given unitary quantum system in bulk geometry. ––- Follow the usual link or contact the organisers (Antoine Bourget and Edoardo Vescovi).
Posted by: IC
Thu
23 Jul 2020
Pre-fundamental representations for the Hubbard model and AdS/CFT
Carlo Meneghelli
(Oxford)
Abstract:
There is a class of representations of quantum groups, referred to as prefundamental representations, that plays an important role in the solution of integrable models. The first example of such representations was given by V. Bazhanov, S. Lukyanov and A. Zamolodchikov in the context of two dimensional conformal field theory in order to construct Baxter Q-operators as transfer matrices. At the same time, there is a rather exceptional quantum group that governs the integrable structure of the one dimensional Hubbard model and plays a fundamental role in the AdS/CFT correspondence. In this talk I will introduce prefundamental representations for this quantum group, explain their basic properties and discuss some of their applications.
––––––- Part of London Integrability Journal Club. New participants please register at integrability-london.weebly.com to receive the link. (Registration is needed only once).
There is a class of representations of quantum groups, referred to as prefundamental representations, that plays an important role in the solution of integrable models. The first example of such representations was given by V. Bazhanov, S. Lukyanov and A. Zamolodchikov in the context of two dimensional conformal field theory in order to construct Baxter Q-operators as transfer matrices. At the same time, there is a rather exceptional quantum group that governs the integrable structure of the one dimensional Hubbard model and plays a fundamental role in the AdS/CFT correspondence. In this talk I will introduce prefundamental representations for this quantum group, explain their basic properties and discuss some of their applications.
––––––- Part of London Integrability Journal Club. New participants please register at integrability-london.weebly.com to receive the link. (Registration is needed only once).
Posted by: andrea
Tue
21 Jul 2020
Superconformal RG Interfaces in Holography
Matthew Cheung
(Imperial College London)
Abstract:
Defects/interfaces/boundaries are interesting objects to study in QFT, and one powerful way to study them is via the use of holography. In this talk, I will discuss our construction of gravitational solutions that holographically describe two different 4d SCFTs joined together at a co-dimension one, planar RG interface and preserving 3d superconformal symmetry. The RG interface we have constructed joins the 4d N=4 SYM theory on one side with the N=1 Leigh-Strassler SCFT on the other. These solutions in general are associated with spatially dependent mass deformations on the N=4 SYM side, but there is a particularly interesting solution for which these deformations vanish. If time allows, I will also discuss another example of our work involving ABJM theory and two 3d N=1 SCFTs with G_2 symmetry. This talk is based on the work hep-th/2007.07891 with Igal Arav, Jerome Gauntlett, Matt Roberts and Chris Rosen. ––- Follow the usual link or contact the organisers (Antoine Bourget and Edoardo Vescovi).
Defects/interfaces/boundaries are interesting objects to study in QFT, and one powerful way to study them is via the use of holography. In this talk, I will discuss our construction of gravitational solutions that holographically describe two different 4d SCFTs joined together at a co-dimension one, planar RG interface and preserving 3d superconformal symmetry. The RG interface we have constructed joins the 4d N=4 SYM theory on one side with the N=1 Leigh-Strassler SCFT on the other. These solutions in general are associated with spatially dependent mass deformations on the N=4 SYM side, but there is a particularly interesting solution for which these deformations vanish. If time allows, I will also discuss another example of our work involving ABJM theory and two 3d N=1 SCFTs with G_2 symmetry. This talk is based on the work hep-th/2007.07891 with Igal Arav, Jerome Gauntlett, Matt Roberts and Chris Rosen. ––- Follow the usual link or contact the organisers (Antoine Bourget and Edoardo Vescovi).
Posted by: IC
Thu
16 Jul 2020
Density matrix for the 2D black hole from an integrable spin chain
Sergei Lukyanov
(Rutgers and Kharkevich IITP)
Abstract:
Twenty years ago Maldacena, Ooguri and Son constructed a modular invariant partition function for the Euclidean black hole (cigar) NLSM. They also proposed an expression for the corresponding density matrix.
This result played a key role in the formulation of
the remarkable conjecture by Ikhlef, Jacobsen and Saleur that the Euclidean black hole NLSM underlies the critical behaviour of a certain integrable spin chain.
In this talk we critically reexamine the above proposals.
The talk is based on the recent (unpublished) joint work with V. Bazhanov and G. Kotousov.
––––––––––––
Part of London Integrability Journal Club. New participants please register at integrability-london.weebly.com to receive the link. (Registration is needed only once).
Twenty years ago Maldacena, Ooguri and Son constructed a modular invariant partition function for the Euclidean black hole (cigar) NLSM. They also proposed an expression for the corresponding density matrix.
This result played a key role in the formulation of
the remarkable conjecture by Ikhlef, Jacobsen and Saleur that the Euclidean black hole NLSM underlies the critical behaviour of a certain integrable spin chain.
In this talk we critically reexamine the above proposals.
The talk is based on the recent (unpublished) joint work with V. Bazhanov and G. Kotousov.
––––––––––––
Part of London Integrability Journal Club. New participants please register at integrability-london.weebly.com to receive the link. (Registration is needed only once).
Posted by: andrea
Wed
15 Jul 2020
D0-brane matrix model and holography
Masanori Hanada
(University of Surrey)
Abstract:
The D0-brane matrix model (the BFSS matrix model and the BMN matrix model) can describe various objects including type IIA black zero-brane, M-theory black hole, M2-branes and M5-branes. We study this theory from several different angles. We put the emphasis on the importance of the dynamics of eigenvalues of matrices, and more generally, color degrees of freedom. Furthermore we explain how the Euclidean theory can be studied by using the Monte Carlo method, and discuss the future directions. If you have a good idea we can test it on computer together!
Part of the Black Hole Information Paradox Journal Club. Please email damian.galante@kcl.ac.uk for link to the meeting.
The D0-brane matrix model (the BFSS matrix model and the BMN matrix model) can describe various objects including type IIA black zero-brane, M-theory black hole, M2-branes and M5-branes. We study this theory from several different angles. We put the emphasis on the importance of the dynamics of eigenvalues of matrices, and more generally, color degrees of freedom. Furthermore we explain how the Euclidean theory can be studied by using the Monte Carlo method, and discuss the future directions. If you have a good idea we can test it on computer together!
Part of the Black Hole Information Paradox Journal Club. Please email damian.galante@kcl.ac.uk for link to the meeting.
Posted by: andrea
Thu
9 Jul 2020
Solving the Yang-Baxter equation
Marius de Leeuw
(Trinity College Dublin)
Abstract:
The Yang-Baxter equation is an important equation that appears in many different areas of physics. It signals the presence of integrable structures which appear in topics ranging from condensed matter physics to holography. In this talk I will discuss a new method to find all regular solutions of the Yang-Baxter equation by using the so-called boost automorphism. The main idea behind this method is to use the Hamiltonian rather than the R-matrix as a starting point. I will demonstrate our method by classifying all solutions of the Yang-Baxter equation of eight-vertex type. I will also consider certain 9x9 and 16x16 solutions and give new integrable models in all of these cases. As a further application, I will discuss all integrable deformations of R-matrices that appear in the lower-dimensional cases of the AdS/CFT correspondence.
––––––––––––– Part of London Integrability Journal Club. New participants please register at
integrability-london.weebly.com for the link. (Registration is only needed once).
The Yang-Baxter equation is an important equation that appears in many different areas of physics. It signals the presence of integrable structures which appear in topics ranging from condensed matter physics to holography. In this talk I will discuss a new method to find all regular solutions of the Yang-Baxter equation by using the so-called boost automorphism. The main idea behind this method is to use the Hamiltonian rather than the R-matrix as a starting point. I will demonstrate our method by classifying all solutions of the Yang-Baxter equation of eight-vertex type. I will also consider certain 9x9 and 16x16 solutions and give new integrable models in all of these cases. As a further application, I will discuss all integrable deformations of R-matrices that appear in the lower-dimensional cases of the AdS/CFT correspondence.
––––––––––––– Part of London Integrability Journal Club. New participants please register at
integrability-london.weebly.com for the link. (Registration is only needed once).
Posted by: andrea
Wed
8 Jul 2020
Remarks on the complex SYK model
Grigory Tarnopolsky
(Harvard)
Abstract:
In this talk I will discuss new properties of the complex SYK model in comparison with the Majorana one. Iรขโฌโขll mostly focus on spectrum of operators and the effective low energy action of the complex SYK model. In this case the conserved U(1) charge contributes a compact scalar field to the effective action in addition to the Schwarzian term.
Part of the Black Hole Information Paradox Journal Club. Please email damian.galante@kcl.ac.uk for link to the meeting.
In this talk I will discuss new properties of the complex SYK model in comparison with the Majorana one. Iรขโฌโขll mostly focus on spectrum of operators and the effective low energy action of the complex SYK model. In this case the conserved U(1) charge contributes a compact scalar field to the effective action in addition to the Schwarzian term.
Part of the Black Hole Information Paradox Journal Club. Please email damian.galante@kcl.ac.uk for link to the meeting.
Posted by: andrea
June 2020
Thu
25 Jun 2020
Exact g-functions
Joao Caetano
(Simons Center)
Abstract:
The g-function is a measure of degrees of freedom associated to a boundary of two-dimensional quantum field theories. In integrable theories, it can be computed exactly in a form of the Fredholm determinant, but it is often hard to evaluate numerically. In this paper, we derive functional equations–-or equivalently integral equations of the thermodynamic Bethe ansatz (TBA) type–-which directly compute the g-function in the simplest integrable theory; the sinh-Gordon theory at the self-dual point. The derivation is based on the classic result by Tracy and Widom on the relation between Fredholm determinants and TBA, which was used also in the context of topological string. As a side result, we present multiple integrals of Q-functions which we conjecture to describe a universal part of the g-function, and discuss its implication to integrable spin chains.
––––––––––––- Part of London Integrability Journal Club. New participants please register at integrability-london.weebly.com to receive the link.
The g-function is a measure of degrees of freedom associated to a boundary of two-dimensional quantum field theories. In integrable theories, it can be computed exactly in a form of the Fredholm determinant, but it is often hard to evaluate numerically. In this paper, we derive functional equations–-or equivalently integral equations of the thermodynamic Bethe ansatz (TBA) type–-which directly compute the g-function in the simplest integrable theory; the sinh-Gordon theory at the self-dual point. The derivation is based on the classic result by Tracy and Widom on the relation between Fredholm determinants and TBA, which was used also in the context of topological string. As a side result, we present multiple integrals of Q-functions which we conjecture to describe a universal part of the g-function, and discuss its implication to integrable spin chains.
––––––––––––- Part of London Integrability Journal Club. New participants please register at integrability-london.weebly.com to receive the link.
Posted by: andrea
Wed
24 Jun 2020
A review of SYK and attempts at a bulk dual
Vladimir Rosenhaus
(IAS)
Abstract:
Most recent discussions of holography in AdS_2/CFT_1 have focused on the Schwarzian and JT gravity. However, the AdS dual of SYK is expected to, in addition, contain an infinite tower of massive fields. The interactions for these fields are in principle fixed by the SYK correlation functions. We review the construction of all-point correlation functions in SYK. We comment on the difficulties in finding a coherent description of the bulk tower of fields.
Part of the Black Hole Information Paradox Journal Club. Please email damian.galante@kcl.ac.uk for link to the meeting.
Most recent discussions of holography in AdS_2/CFT_1 have focused on the Schwarzian and JT gravity. However, the AdS dual of SYK is expected to, in addition, contain an infinite tower of massive fields. The interactions for these fields are in principle fixed by the SYK correlation functions. We review the construction of all-point correlation functions in SYK. We comment on the difficulties in finding a coherent description of the bulk tower of fields.
Part of the Black Hole Information Paradox Journal Club. Please email damian.galante@kcl.ac.uk for link to the meeting.
Posted by: andrea
Tue
23 Jun 2020
Challenging the Inflationary Paradigm
Eugene Lim
(King's College London)
Abstract:
Inflation is now the paradigmatic theory of the Big Bang. But is it deserved? I will describe the conceptual and theoretical challenges that Inflation is still facing, argue that we should keep an open mind. In particular, I will argue that while it is a theory that claims to be a theory of initial conditions of the Universe, successful inflation actually depends on an intimate interplay between its own initial conditions and the inflationary model. I will show how one might go about probing this interplay by testing whether inflation can begin if its own initial conditions are not homogenous. ––- Follow the usual link or contact the organisers (Antoine Bourget and Edoardo Vescovi). Student introduction at 13:00.
Inflation is now the paradigmatic theory of the Big Bang. But is it deserved? I will describe the conceptual and theoretical challenges that Inflation is still facing, argue that we should keep an open mind. In particular, I will argue that while it is a theory that claims to be a theory of initial conditions of the Universe, successful inflation actually depends on an intimate interplay between its own initial conditions and the inflationary model. I will show how one might go about probing this interplay by testing whether inflation can begin if its own initial conditions are not homogenous. ––- Follow the usual link or contact the organisers (Antoine Bourget and Edoardo Vescovi). Student introduction at 13:00.
Posted by: IC
Wed
17 Jun 2020
On higher-spin theory in two dimensions
Xavier Bekaert
(Tours (France))
Abstract:
We aim at formulating a higher-spin gravity theory around AdS2 relevant
for holography. As a first step, we investigate its kinematics by
identifying the low-dimensional cousins of the standard higher-dimensional
structures in higher-spin gravity such as the singleton, the higher-spin
symmetry algebra, the higher-rank gauge and matter fields, etc.
We aim at formulating a higher-spin gravity theory around AdS2 relevant
for holography. As a first step, we investigate its kinematics by
identifying the low-dimensional cousins of the standard higher-dimensional
structures in higher-spin gravity such as the singleton, the higher-spin
symmetry algebra, the higher-rank gauge and matter fields, etc.
Posted by: IC
Wed
17 Jun 2020
A new observable to decode emergent gravity
Josephine Suh
(Caltech)
Abstract:
I review the emergence of JT gravity from the SYK model, and the calculation of correlation functions in JT gravity. I motivate the need for a new observable distinct from entanglement entropy to fully decode emergent gravity, and propose as such an observable a quantum generalization of the entropy of multiple measurements on a dynamical system.
Part of the Black Hole Information Paradox Journal Club. Please email damian.galante@kcl.ac.uk for link to the meeting.
I review the emergence of JT gravity from the SYK model, and the calculation of correlation functions in JT gravity. I motivate the need for a new observable distinct from entanglement entropy to fully decode emergent gravity, and propose as such an observable a quantum generalization of the entropy of multiple measurements on a dynamical system.
Part of the Black Hole Information Paradox Journal Club. Please email damian.galante@kcl.ac.uk for link to the meeting.
Posted by: andrea
Fri
12 Jun 2020
Discussion about replica wormholes and ensembles
Douglas Stanford
(Stanford)
Abstract:
The goal is to have a general discussion about replica wormholes and the black hole information problem. To start things off, we will discuss the question of whether an ensemble interpretation is necessary for the replica wormhole computations of the entropy.
Part of the Black Hole Information Paradox Journal Club. Please email damian.galante@kcl.ac.uk for link to the meeting.
NOTE THAT THE TIME/DATE OF THE TALK HAS BEEN CHANGED.
The goal is to have a general discussion about replica wormholes and the black hole information problem. To start things off, we will discuss the question of whether an ensemble interpretation is necessary for the replica wormhole computations of the entropy.
Part of the Black Hole Information Paradox Journal Club. Please email damian.galante@kcl.ac.uk for link to the meeting.
NOTE THAT THE TIME/DATE OF THE TALK HAS BEEN CHANGED.
Posted by: QMW
Thu
11 Jun 2020
Fishnet CFT: TBA and Non-compact Spin Chain
Gwenael Ferrando
(ENS Paris)
Abstract:
The fishnet CFT is a non-unitary CFT of two matrix complex scalar fields interacting via a single quartic potential. The chiral nature of the interaction strongly constrains the Feynman diagrams arising at each order in perturbation theory, those that survive are of fishnet type. In this talk, I will present the TBA equations for the conformal dimensions of multi-magnon local operators in this theory. I will emphasize the need to diagonalize suitable graph-building operators in order to determine the asymptotic data, dispersion relation and S matrix, on which the TBA relies. A dual version of the TBA equations, relating D-dimensional graphs to two-dimensional sigma models, will also be examined. The last part of the talk will be devoted to the presentation of the underlying non-compact spin chain and of additional results regarding diagonalization of graph-building operators.
––––––––––- Part of London Integrability Journal Club. New participants please register at integrability-london.weebly.com for the link.
The fishnet CFT is a non-unitary CFT of two matrix complex scalar fields interacting via a single quartic potential. The chiral nature of the interaction strongly constrains the Feynman diagrams arising at each order in perturbation theory, those that survive are of fishnet type. In this talk, I will present the TBA equations for the conformal dimensions of multi-magnon local operators in this theory. I will emphasize the need to diagonalize suitable graph-building operators in order to determine the asymptotic data, dispersion relation and S matrix, on which the TBA relies. A dual version of the TBA equations, relating D-dimensional graphs to two-dimensional sigma models, will also be examined. The last part of the talk will be devoted to the presentation of the underlying non-compact spin chain and of additional results regarding diagonalization of graph-building operators.
––––––––––- Part of London Integrability Journal Club. New participants please register at integrability-london.weebly.com for the link.
Posted by: andrea
Thu
11 Jun 2020
Supersymmetric S-folds
Adolfo Guarino
(Oviedo)
Abstract:
I will discuss recent progress towards understanding geometric and holographic aspects of electromagnetic duality in four-dimensional supergravity. More concretely, I will focus on the connection between electromagnetic duality and the existence of new classes of supersymmetric S-fold backgrounds of type IIB supergravity. These provide natural candidates to holographically describe new strongly coupled three-dimensional CFTรขโฌโขs which are localised on interfaces of N=4 super-Yang-Mills theory.
I will discuss recent progress towards understanding geometric and holographic aspects of electromagnetic duality in four-dimensional supergravity. More concretely, I will focus on the connection between electromagnetic duality and the existence of new classes of supersymmetric S-fold backgrounds of type IIB supergravity. These provide natural candidates to holographically describe new strongly coupled three-dimensional CFTรขโฌโขs which are localised on interfaces of N=4 super-Yang-Mills theory.
Posted by: IC
Tue
9 Jun 2020
A Quantum Lab for Quantum Field Theory
Steven Abel
(Durham University)
Abstract:
In this pedagogical talk I will discuss recent and ongoing work showing how quantum field theory problems can be embedded on to quantum annealers. The general method we use is a discretisation of the field theory problem into a general Ising model, with the continuous field values being encoded into Ising spin chains. To illustrate the method, and as a simple proof of principle, we have used a quantum annealer to recover the correct profile of various tunnelling solutions. Then I will discuss current work where we construct actual quantum tunnelling processes involving instantons. These methods are applicable to many nonperturbative problems. ––- Follow the usual link or contact the organisers (Antoine Bourget and Edoardo Vescovi).
In this pedagogical talk I will discuss recent and ongoing work showing how quantum field theory problems can be embedded on to quantum annealers. The general method we use is a discretisation of the field theory problem into a general Ising model, with the continuous field values being encoded into Ising spin chains. To illustrate the method, and as a simple proof of principle, we have used a quantum annealer to recover the correct profile of various tunnelling solutions. Then I will discuss current work where we construct actual quantum tunnelling processes involving instantons. These methods are applicable to many nonperturbative problems. ––- Follow the usual link or contact the organisers (Antoine Bourget and Edoardo Vescovi).
Posted by: IC
Thu
4 Jun 2020
Crossing equations for mixed flux AdS3/CFT2 (UNUSUAL TIME)
Olof Ohlsson Sax
(NORDITA)
Abstract:
I will give an overview of recent progress in understanding string theory in AdS3 backgrounds with a mixture of Ramond-Ramond and Neveu-Schwarz-Neveu-Schwarz three-form flux. Such theories are integrable, but provide many features not encountered in the more familiar case of pure Ramond-Ramond flux. In this talk I will explore the analytic structure of the dispersion relation of the world-sheet excitations and how it relates to the crossing equations of the two-particle S matrix. Determining the dressing phases of the mixed flux S matrix is the next major step in using integrability to the AdS3/CFT2 correspondence.
–––– Part of London Integrability Journal Club. New participants please register at integrability-london.weebly.com to receive the link.
I will give an overview of recent progress in understanding string theory in AdS3 backgrounds with a mixture of Ramond-Ramond and Neveu-Schwarz-Neveu-Schwarz three-form flux. Such theories are integrable, but provide many features not encountered in the more familiar case of pure Ramond-Ramond flux. In this talk I will explore the analytic structure of the dispersion relation of the world-sheet excitations and how it relates to the crossing equations of the two-particle S matrix. Determining the dressing phases of the mixed flux S matrix is the next major step in using integrability to the AdS3/CFT2 correspondence.
–––– Part of London Integrability Journal Club. New participants please register at integrability-london.weebly.com to receive the link.
Posted by: andrea
Wed
3 Jun 2020
Spherical Branes, Supersymmetric Localization, and Holography
Nikolay Bobev
(KUL Leuven)
Abstract:
I will describe a class of supergravity solutions holographically dual to d-dimensional maximally supersymmetric SYM on S^d. Supersymmetric localization can be employed to calculate the partition function and the VEV of a 1/2-BPS Wilson lines in the planar limit of the SYM theory. I will present the results of this calculation and will show how they lead to a non-trivial precision test of holography in the context of non-conformal QFTs and space-times that are non asymptotically locally AdS.
I will describe a class of supergravity solutions holographically dual to d-dimensional maximally supersymmetric SYM on S^d. Supersymmetric localization can be employed to calculate the partition function and the VEV of a 1/2-BPS Wilson lines in the planar limit of the SYM theory. I will present the results of this calculation and will show how they lead to a non-trivial precision test of holography in the context of non-conformal QFTs and space-times that are non asymptotically locally AdS.
Posted by: IC
Wed
3 Jun 2020
From bulk reconstruction to Berry phases and back
Bartlomiej Czech
(IAS, Tsinghua U.)
Abstract:
The first half of the talk will be a review of the main ingredients of bulk reconstruction: the Ryu-Takayanagi formula and subregion duality, the JLMS theorem, error correction and the complexity conjecture. The second half will be about my recent and current work on "modular Berry phases"–a type of Berry phase which characterizes the entanglement structure of a quantum state. We will see that the bulk curvature in AdS is (up to an integral transform) a special case of the modular Berry phase, though the concept has many other applications which we may or may not discuss.
<p>
</p>
Part of the Black Hole Information Paradox Journal Club. Please email <a href="mailto:damian.galante@kcl.ac.uk">damian.galante@kcl.ac.uk</a> for Zoom link to the meeting.
The first half of the talk will be a review of the main ingredients of bulk reconstruction: the Ryu-Takayanagi formula and subregion duality, the JLMS theorem, error correction and the complexity conjecture. The second half will be about my recent and current work on "modular Berry phases"–a type of Berry phase which characterizes the entanglement structure of a quantum state. We will see that the bulk curvature in AdS is (up to an integral transform) a special case of the modular Berry phase, though the concept has many other applications which we may or may not discuss.
<p>
</p>
Part of the Black Hole Information Paradox Journal Club. Please email <a href="mailto:damian.galante@kcl.ac.uk">damian.galante@kcl.ac.uk</a> for Zoom link to the meeting.
Posted by: andrea
May 2020
Thu
28 May 2020
Boundary states, overlaps, nesting and bootstrapping AdS/dCFT
Tamas Gombor
(Wigner Research Center, Budapest)
Abstract:
Recently there have been renewed interest and relevant progress in calculating overlaps between periodic multiparticle states and integrable boundary states. They appear in quite distinct parts of theoretical physics including statistical physics and the gauge/string duality.
I will give a summary of known overlap formulas and analyze the connection between selection rules and symmetries. I will introduce a nesting procedure for boundary states which provides the factorizing overlaps for higher rank algebras automatically. This method can be used for the calculation of the asymptotic all-loop 1-point functions in AdS/dCFT. In doing so I will present the solutions of the YBE for the K-matrices with centrally extended su(2|2) symmetry and the generic overlaps of the corresponding boundary states.
Based on 2004.11329
––––––––––––- Part of London Integrability Journal Club. Please register at integrability-london.weebly.com/ for the zoom link
Recently there have been renewed interest and relevant progress in calculating overlaps between periodic multiparticle states and integrable boundary states. They appear in quite distinct parts of theoretical physics including statistical physics and the gauge/string duality.
I will give a summary of known overlap formulas and analyze the connection between selection rules and symmetries. I will introduce a nesting procedure for boundary states which provides the factorizing overlaps for higher rank algebras automatically. This method can be used for the calculation of the asymptotic all-loop 1-point functions in AdS/dCFT. In doing so I will present the solutions of the YBE for the K-matrices with centrally extended su(2|2) symmetry and the generic overlaps of the corresponding boundary states.
Based on 2004.11329
––––––––––––- Part of London Integrability Journal Club. Please register at integrability-london.weebly.com/ for the zoom link
Posted by: andrea
Thu
28 May 2020
From Scattering Amplitudes to Results in General Relativity (email p.agarwal AT qmul.ac.uk for the zoom link)
Emil Bjerrum-Bohr
( Niels Bohr Institute)
Abstract:
Gravity is a fundamental theory of physics, but so weak, that we still know very little about it. A new exciting development is that the Laser Interferometer Gravitational-Wave Observatory (LIGO) can now measure the effects when massive black holes collide in the Universe. This has stimulated many new and interesting studies of gravitational interactions. I will in this talk discuss recent computational advances and discuss how to derive results for observables in general relativity from amplitudes.
Gravity is a fundamental theory of physics, but so weak, that we still know very little about it. A new exciting development is that the Laser Interferometer Gravitational-Wave Observatory (LIGO) can now measure the effects when massive black holes collide in the Universe. This has stimulated many new and interesting studies of gravitational interactions. I will in this talk discuss recent computational advances and discuss how to derive results for observables in general relativity from amplitudes.
Posted by: QMW
Wed
27 May 2020
Higher-derivative supergravity for AdS4 holography
๐ London
Kiril Hristov
(INRNE, Bulgarian Academy of Sciences)
Abstract:
In this talk I discuss some work in progress concerning higher-derivative (HD) terms in 4d supergravity. In particular we'll focus
on the simplest case of 4-derivative terms appearing in minimal gauged
supergravity. This choice minimizes the freedom in the HD terms to two
arbitrary constants, which can be determined by a holographic match. This gives a prediction about the reduction of 11d HD terms on S^7. We then derive holographic predictions for the first subleading terms of various supersymmetric partition functions in their expansion of the gauge group rank, N. Additionally we are able to evaluate the on-shell action for non-BPS solutions in supergravity, allowing us to discuss black hole thermodynamics in the presence of HD terms.
(To request the Zoom link send email with empty text and subject "talk" to alejandro.cabo_bizet@kcl.ac.uk)
In this talk I discuss some work in progress concerning higher-derivative (HD) terms in 4d supergravity. In particular we'll focus
on the simplest case of 4-derivative terms appearing in minimal gauged
supergravity. This choice minimizes the freedom in the HD terms to two
arbitrary constants, which can be determined by a holographic match. This gives a prediction about the reduction of 11d HD terms on S^7. We then derive holographic predictions for the first subleading terms of various supersymmetric partition functions in their expansion of the gauge group rank, N. Additionally we are able to evaluate the on-shell action for non-BPS solutions in supergravity, allowing us to discuss black hole thermodynamics in the presence of HD terms.
(To request the Zoom link send email with empty text and subject "talk" to alejandro.cabo_bizet@kcl.ac.uk)
Posted by: andrea
Tue
26 May 2020
Constraining Modified Gravity Models with Casimir Force Experiments
Anne-Christine Davis
(University of Cambridge)
Abstract:
Modified gravity models have been developed to try to explain the observed acceleration of the expansion of the Universe. Such models introduce and extra, fifth force, and usually employ a screening mechanism whereby the fifth force is screened in the solar system but unscreened cosmologically. Recent developments in laboratory experiments mean that such theories can now be tested and constrained using existing experiments. In particular innovative Casimir force experiments can be used to constrain such theories. This enables Einstein gravity to be tested on scales not previously explored. ––- Follow the usual link or contact the organisers (Antoine Bourget and Edoardo Vescovi). Student introduction at 13:00.
Modified gravity models have been developed to try to explain the observed acceleration of the expansion of the Universe. Such models introduce and extra, fifth force, and usually employ a screening mechanism whereby the fifth force is screened in the solar system but unscreened cosmologically. Recent developments in laboratory experiments mean that such theories can now be tested and constrained using existing experiments. In particular innovative Casimir force experiments can be used to constrain such theories. This enables Einstein gravity to be tested on scales not previously explored. ––- Follow the usual link or contact the organisers (Antoine Bourget and Edoardo Vescovi). Student introduction at 13:00.
Posted by: IC
Thu
21 May 2020
Some remarks on the interface of arithmetic geometry and quantum field theory (email p.agarwal AT qmul.ac.uk)
Minhyong Kim
(University of Oxford)
Abstract:
Arithmetic geometry is the study *arithmetic schemes*, mathematical structures that have simultaneously an arithmetic and a geometric structure. The prototype is the so-called *spectrum of the integers* which is a geometric object on which the integers form the ring of functions. I will explain some of the difficult and classical problems that arise in their study, and how ideas of physics, especially topological quantum field theory, may be helpful.
Arithmetic geometry is the study *arithmetic schemes*, mathematical structures that have simultaneously an arithmetic and a geometric structure. The prototype is the so-called *spectrum of the integers* which is a geometric object on which the integers form the ring of functions. I will explain some of the difficult and classical problems that arise in their study, and how ideas of physics, especially topological quantum field theory, may be helpful.
Posted by: QMW
Thu
21 May 2020
Integrable Field Theories with an Interacting Massless Sector
Ines Aniceto
(University of Southampton)
Abstract:
Integrability techniques have played a major role in the study the AdS/CFT correspondence, providing an accurate description of different string theoretic observables beyond the weak or strong coupling perturbation theory. However, the case of string on certain AdS_3 backgrounds provided new challenges in the form of massless excitations. Difficulties in incorporating these into the integrable description have led to disagreements concerning the energy of massive physical states.
In general integrable theories, massless and massive sectors can generally be treated separately. We know this cannot be the case in AdS_3, but a full TBA description of the interaction between the sectors is yet to be found. Surprisingly, such a description can found in a family of integrable field theories รขโฌโ homogeneous sine-Gordon models. Here, one can take a double scaling limit of the adjustable parameters and zoom into a regime described by a TBA where the massless sector does not decouple and contributes to the energy of massive particles at the same order as for which the Bethe ansatz would suffice in a massive theory.
–––- Part of London Integrability Journal Club. Please register at integrability-london.weebly.com for the link.
Integrability techniques have played a major role in the study the AdS/CFT correspondence, providing an accurate description of different string theoretic observables beyond the weak or strong coupling perturbation theory. However, the case of string on certain AdS_3 backgrounds provided new challenges in the form of massless excitations. Difficulties in incorporating these into the integrable description have led to disagreements concerning the energy of massive physical states.
In general integrable theories, massless and massive sectors can generally be treated separately. We know this cannot be the case in AdS_3, but a full TBA description of the interaction between the sectors is yet to be found. Surprisingly, such a description can found in a family of integrable field theories รขโฌโ homogeneous sine-Gordon models. Here, one can take a double scaling limit of the adjustable parameters and zoom into a regime described by a TBA where the massless sector does not decouple and contributes to the energy of massive particles at the same order as for which the Bethe ansatz would suffice in a massive theory.
–––- Part of London Integrability Journal Club. Please register at integrability-london.weebly.com for the link.
Posted by: andrea
Wed
20 May 2020
TBA
Yang-Hui He
(Oxford)
Abstract:
TBA
TBA
Posted by: IC
Tue
19 May 2020
The classical double copy
Chris White
(Queen Mary, University of London)
Abstract:
Non-abelian gauge theories underly particle physics, including collision processes at particle accelerators. Recently, quantum scattering probabilities in gauge theories have been shown to be closely related to their counterparts in gravity theories, by the so-called "double copy". This suggests a deep relationship between two very different areas of physics, and may lead to new insights into quantum gravity, as well as novel new computational methods. This talk will review the double copy for amplitudes, before discussing how it may be extended to describe exact classical solutions such as black holes. I will then look at recent work which aims to generalise the double copy yet further, and conclude with an outlook of current open problems. ––- Follow the usual link or contact the organisers (Antoine Bourget and Edoardo Vescovi). Student introduction at 13:00.
Non-abelian gauge theories underly particle physics, including collision processes at particle accelerators. Recently, quantum scattering probabilities in gauge theories have been shown to be closely related to their counterparts in gravity theories, by the so-called "double copy". This suggests a deep relationship between two very different areas of physics, and may lead to new insights into quantum gravity, as well as novel new computational methods. This talk will review the double copy for amplitudes, before discussing how it may be extended to describe exact classical solutions such as black holes. I will then look at recent work which aims to generalise the double copy yet further, and conclude with an outlook of current open problems. ––- Follow the usual link or contact the organisers (Antoine Bourget and Edoardo Vescovi). Student introduction at 13:00.
Posted by: IC
Fri
15 May 2020
Wilson loops as Matrix Product States (NOTE UNUSUAL TIME AND DAY)
Shota Komatsu
(IAS)
Abstract:
In his paper in 1979, Polyakov envisaged a possibility of reformulating the gauge theory as a Principal Chiral Model defined on a space of loops and discussed "the loop-space integrability". This idea, together with a closely related idea of the loop equation, led to numerous important results in matrix models and 2d gauge theories, but its application to four-dimensional gauge theories had only limited success. Now, after 50 years, we have a concrete example of integrable four-dimensional gauge theory, N=4 SYM. However integrability in N=4 SYM is formulated mostly in terms of local operators, although important progress has been made in constructing the Yangian for the Wilson loops. In this talk, I will present a framework which would bridge these two distant notions of integrabililty. The key player in the story is a correlation function of a local operator and the Wilson loop. I reformulate the gauge-theory computation of this observable as an overlap between an energy eigenstate of a spin chain and a matrix product state (MPS). Unlike standard MPS's discussed in the literature, our MPS has infinite bond dimensions in order to accommodate infinite dimensionality of the space of loops. It provides an "intertwiner" between integrable structures of the local operators and the Wilson loops, and in particular implies the existence of a special set of deformations of the Wilson loop which satisfy the QQ-relation. I will also explain how to formulate a nonperturbative bootstrap program based on the results obtained in this framework and compute the correlator of the circular BPS Wilson loop and general non-BPS operators at finite coupling, emphasizing the relation to and the difference from other observables that were computed by a similar approach.
––––––––-
Part of London Integrability Journal Club. Please register using the form at integrability-london.weebly.com
In his paper in 1979, Polyakov envisaged a possibility of reformulating the gauge theory as a Principal Chiral Model defined on a space of loops and discussed "the loop-space integrability". This idea, together with a closely related idea of the loop equation, led to numerous important results in matrix models and 2d gauge theories, but its application to four-dimensional gauge theories had only limited success. Now, after 50 years, we have a concrete example of integrable four-dimensional gauge theory, N=4 SYM. However integrability in N=4 SYM is formulated mostly in terms of local operators, although important progress has been made in constructing the Yangian for the Wilson loops. In this talk, I will present a framework which would bridge these two distant notions of integrabililty. The key player in the story is a correlation function of a local operator and the Wilson loop. I reformulate the gauge-theory computation of this observable as an overlap between an energy eigenstate of a spin chain and a matrix product state (MPS). Unlike standard MPS's discussed in the literature, our MPS has infinite bond dimensions in order to accommodate infinite dimensionality of the space of loops. It provides an "intertwiner" between integrable structures of the local operators and the Wilson loops, and in particular implies the existence of a special set of deformations of the Wilson loop which satisfy the QQ-relation. I will also explain how to formulate a nonperturbative bootstrap program based on the results obtained in this framework and compute the correlator of the circular BPS Wilson loop and general non-BPS operators at finite coupling, emphasizing the relation to and the difference from other observables that were computed by a similar approach.
––––––––-
Part of London Integrability Journal Club. Please register using the form at integrability-london.weebly.com
Posted by: andrea
Thu
14 May 2020
An exact AdS/CFT duality (please email p.agarwal AT qmul.ac.uk for the zoom link)
Matthias Gaberdiel
(ETH Zurich)
Abstract:
String theory on AdS3 x S3 x T4 with one unit of NS-NS flux is argued to be exactly dual to the symmetric orbifold of T4 in the large N limit. The string theory background can be described in terms of a solvable world-sheet theory. This allows one to compute the complete single-string spacetime spectrum and thereby demonstrate that it agrees with the that of the symmetric orbifold of T4. Furthermore, the structure of the symmetric orbifold correlators can be reproduced from the world-sheet perspective.
String theory on AdS3 x S3 x T4 with one unit of NS-NS flux is argued to be exactly dual to the symmetric orbifold of T4 in the large N limit. The string theory background can be described in terms of a solvable world-sheet theory. This allows one to compute the complete single-string spacetime spectrum and thereby demonstrate that it agrees with the that of the symmetric orbifold of T4. Furthermore, the structure of the symmetric orbifold correlators can be reproduced from the world-sheet perspective.
Posted by: QMW
Wed
13 May 2020
(Quantum) Higher Spin Gravity and Physics
Evgeny Skvortsov
(Albert Einstein Institute (Potsdam))
Abstract:
I will give a general overview of Higher Spin Gravities and also discuss the recent developments
that give a class of models where UV-divergences of Einstein gravity cancel out thanks to the higher spin symmetry.
At the end I will discuss the relation between Higher Spin Gravities and a class of conformal field theories in three dimensions
that describe the physics of many second order phase transitions in the real world and have been recently conjectured to exhibit a number
of remarkable dualities, in particular the three-dimensional bosonization duality. I will show how Higher Spin Gravity can help to prove the dualities
and how it makes new predictions. The relation to QCD and self-dual Yang-Mills will also be discussed.
I will give a general overview of Higher Spin Gravities and also discuss the recent developments
that give a class of models where UV-divergences of Einstein gravity cancel out thanks to the higher spin symmetry.
At the end I will discuss the relation between Higher Spin Gravities and a class of conformal field theories in three dimensions
that describe the physics of many second order phase transitions in the real world and have been recently conjectured to exhibit a number
of remarkable dualities, in particular the three-dimensional bosonization duality. I will show how Higher Spin Gravity can help to prove the dualities
and how it makes new predictions. The relation to QCD and self-dual Yang-Mills will also be discussed.
Posted by: IC
Tue
12 May 2020
Phenomenological Applications of the EFTs for Condensed Matter
Angelo Esposito
(Ecole polytechnique federale de Lausanne)
Abstract:
In this talk I will review the general ideas behind the recently developed relativistic effective field theories (EFTs) for different phases of matter (spontaneous symmetry breaking, Goldstone theorem, etc.). I will put particular emphasis on concretely building an EFT for the description of collective excitations in zero-temperature superfluids, which is the simplest of these theories. I will then argue that these methods, borrowed from high energy theory ideology, are mature enough to be successfully applied to phenomenologically relevant problems. In this direction, I will present two applications: (1) the calculation of the gravitational mass transported by a sound wave in a nonrelativistic medium (superfluid, fluid and solid), and (2) the study of the response of a He-4 detector to the passage of sub-MeV dark matter particle. ––- Follow the link in use since May 5th or contact the organisers (Antoine Bourget and Edoardo Vescovi). Student introduction at 13:00.
In this talk I will review the general ideas behind the recently developed relativistic effective field theories (EFTs) for different phases of matter (spontaneous symmetry breaking, Goldstone theorem, etc.). I will put particular emphasis on concretely building an EFT for the description of collective excitations in zero-temperature superfluids, which is the simplest of these theories. I will then argue that these methods, borrowed from high energy theory ideology, are mature enough to be successfully applied to phenomenologically relevant problems. In this direction, I will present two applications: (1) the calculation of the gravitational mass transported by a sound wave in a nonrelativistic medium (superfluid, fluid and solid), and (2) the study of the response of a He-4 detector to the passage of sub-MeV dark matter particle. ––- Follow the link in use since May 5th or contact the organisers (Antoine Bourget and Edoardo Vescovi). Student introduction at 13:00.
Posted by: IC
Thu
7 May 2020
Completeness of Bethe equations
Dmytro Volin
(Uppsala University)
Abstract:
We review a proof of bijection between eigenstates of the Bethe algebra and solutions of Bethe equations written as a Wronskian quantisation condition or as QQ-relations on Young diagrams. Furthermore, it is demonstrated that the Bethe algebra is maximal commutative and it has simple spectrum every time it is diagonalisable. The proof covers rational gl(m|n) spin chains in the defining representation with the famous Heisenberg spin chain being a particular subcase. The proof is rigorous (no general position arguments are used). We do not rely on the string hypothesis and moreover we conjecture a precise meaning of Bethe strings as a consequence of the proposed proof.
A short introduction with necessary facts about polynomial rings will be given at the beginning of the talk.
Based on 2004.02865
NOTE: Part of London Integrability Journal Club. Please register at integrability-london.weebly.com to participate.
We review a proof of bijection between eigenstates of the Bethe algebra and solutions of Bethe equations written as a Wronskian quantisation condition or as QQ-relations on Young diagrams. Furthermore, it is demonstrated that the Bethe algebra is maximal commutative and it has simple spectrum every time it is diagonalisable. The proof covers rational gl(m|n) spin chains in the defining representation with the famous Heisenberg spin chain being a particular subcase. The proof is rigorous (no general position arguments are used). We do not rely on the string hypothesis and moreover we conjecture a precise meaning of Bethe strings as a consequence of the proposed proof.
A short introduction with necessary facts about polynomial rings will be given at the beginning of the talk.
Based on 2004.02865
NOTE: Part of London Integrability Journal Club. Please register at integrability-london.weebly.com to participate.
Posted by: andrea
Thu
7 May 2020
The Precision Frontier in LHC Simulations (please email p.agarwal AT qmul.ac.uk for a link to the zoom meeting)
Frank Krauss
(Durham University)
Abstract:
In my talk, I will introduce concepts relevant for simulation of LHC physics. I will highlight some of the challenges when going to the level of precision necessary to match experimental accuracy.
In my talk, I will introduce concepts relevant for simulation of LHC physics. I will highlight some of the challenges when going to the level of precision necessary to match experimental accuracy.
Posted by: QMW
Wed
6 May 2020
A personal bird eye view of fuzzballs
Rodolfo Russo
(QMUL)
Abstract:
There are indications that "traditional" GR physics at the horizon and usual assumptions of locality cannot provide a consistent description of black holes. The fuzzball paradigm suggests that "traditional" GR physics at the horizon should be relaxed and that string theory provides the right degrees of freedom to have a non-trivial structure at the scale of the horizon. I'll review how this idea has emerged from the analysis of the Strominger-Vafa black hole and its implication for the AdS3/CFT2 duality. For link to the meeting, please email <a href="mailto:damian.galante@kcl.ac.uk">damian.galante@kcl.ac.uk</a>.
There are indications that "traditional" GR physics at the horizon and usual assumptions of locality cannot provide a consistent description of black holes. The fuzzball paradigm suggests that "traditional" GR physics at the horizon should be relaxed and that string theory provides the right degrees of freedom to have a non-trivial structure at the scale of the horizon. I'll review how this idea has emerged from the analysis of the Strominger-Vafa black hole and its implication for the AdS3/CFT2 duality. For link to the meeting, please email <a href="mailto:damian.galante@kcl.ac.uk">damian.galante@kcl.ac.uk</a>.
Posted by: andrea
Tue
5 May 2020
Inflation and Geometry
Sebastien Renaux-Petel
(Institut d'Astrophysique de Paris)
Abstract:
Inflation, an era of accelerated expansion of the universe prior to the radiation phase, constitutes the paradigm of primordial cosmology. Within this paradigm, the simplest single-field slow-roll models economically explain all current data. However, the sensitivity of inflation to Planck scale physics, and the fact that ultraviolet completions of inflation invariably involve extra fields coupled to the inflaton, indicate that these models constitute at best a phenomenological description that emerges from a more realistic physical framework.
In this talk, I will describe recent works that aim at understanding the consequences of the presence of several degrees of freedom during inflation. In particular, I will highlight that realistic models are characterized not only by their potentials but also by the internal geometries in which the fields live in, and I will discuss related novel phenomena that have been studied in the past years. ––- Contact the organisers (Antoine Bourget and Edoardo Vescovi) for the link.
Inflation, an era of accelerated expansion of the universe prior to the radiation phase, constitutes the paradigm of primordial cosmology. Within this paradigm, the simplest single-field slow-roll models economically explain all current data. However, the sensitivity of inflation to Planck scale physics, and the fact that ultraviolet completions of inflation invariably involve extra fields coupled to the inflaton, indicate that these models constitute at best a phenomenological description that emerges from a more realistic physical framework.
In this talk, I will describe recent works that aim at understanding the consequences of the presence of several degrees of freedom during inflation. In particular, I will highlight that realistic models are characterized not only by their potentials but also by the internal geometries in which the fields live in, and I will discuss related novel phenomena that have been studied in the past years. ––- Contact the organisers (Antoine Bourget and Edoardo Vescovi) for the link.
Posted by: IC
April 2020
Thu
30 Apr 2020
Computing scalar products in the Bethe Ansatz
Juan Miguel Nieto Garcia
(University of Surrey)
Abstract:
Computing scalar products is a non-trivial problem in the context of the Algebraic Bethe Ansatz. In this talk I comment about the different problems one encounter and how to easily compute recurrence relations for scalar products, even beyond SU(2). I will also present a possible explanation for the existence of determinant representations of the scalar products.
NOTE: Part of London Integrability Journal Club. Please register at integrability-london.weebly.com
Computing scalar products is a non-trivial problem in the context of the Algebraic Bethe Ansatz. In this talk I comment about the different problems one encounter and how to easily compute recurrence relations for scalar products, even beyond SU(2). I will also present a possible explanation for the existence of determinant representations of the scalar products.
NOTE: Part of London Integrability Journal Club. Please register at integrability-london.weebly.com
Posted by: andrea
Thu
30 Apr 2020
Color Confinement and Bose-Einstein condensation (please email p.agarwal AT qmul.ac.uk for a link to the zoom meeting))
Masanori Hanada
(University of Surrey)
Abstract:
We propose a unified description of two important phenomena: color confinement in large-N gauge theory, and Bose-Einstein condensation (BEC). We focus on the confinement/deconfinement transition characterized by the increase of the entropy from N^0 to N^2, which persists in the weak coupling region. Indistinguishability associated with the symmetry group –- SU(N) or O(N) in gauge theory, and S_N permutations in the system of identical bosons –- is crucial for the formation of the condensed (confined) phase. We relate standard criteria, based on off-diagonal long range order (ODLRO) for BEC and the Polyakov loop for gauge theory. The constant offset of the distribution of the phases of the Polyakov loop corresponds to ODLRO, and gives the order parameter for the partially-(de)confined phase at finite coupling. Furthermore we show the numerical evidence for this phenomenon at strong coupling, by using the Yang-Mills matrix model as a concrete example and solving it numerical via lattice simulation.
This talk is based on a series of papers, especially "Color Confinement and Bose-Einstein Condensation" by Hanada, Shimada and Wintergerst, 2001.10459 [hep-th] and "Partial Deconfinement at Strong Coupling on a Lattice' by Bergner, Bodendorfer, Funai, Hanada, Rinaldi, Schaefer, Vranas and Watanabe to appear (should be in hep-th by the talk).
We propose a unified description of two important phenomena: color confinement in large-N gauge theory, and Bose-Einstein condensation (BEC). We focus on the confinement/deconfinement transition characterized by the increase of the entropy from N^0 to N^2, which persists in the weak coupling region. Indistinguishability associated with the symmetry group –- SU(N) or O(N) in gauge theory, and S_N permutations in the system of identical bosons –- is crucial for the formation of the condensed (confined) phase. We relate standard criteria, based on off-diagonal long range order (ODLRO) for BEC and the Polyakov loop for gauge theory. The constant offset of the distribution of the phases of the Polyakov loop corresponds to ODLRO, and gives the order parameter for the partially-(de)confined phase at finite coupling. Furthermore we show the numerical evidence for this phenomenon at strong coupling, by using the Yang-Mills matrix model as a concrete example and solving it numerical via lattice simulation.
This talk is based on a series of papers, especially "Color Confinement and Bose-Einstein Condensation" by Hanada, Shimada and Wintergerst, 2001.10459 [hep-th] and "Partial Deconfinement at Strong Coupling on a Lattice' by Bergner, Bodendorfer, Funai, Hanada, Rinaldi, Schaefer, Vranas and Watanabe to appear (should be in hep-th by the talk).
Posted by: QMW
Tue
28 Apr 2020
Bootstrapping Cosmological Correlations
Daniel Baumann
(University of Amsterdam)
Abstract:
The past decade has seen an explosion of progress in our understanding of scattering amplitudes in gauge theory and gravity. New bootstrap methods have revealed hidden symmetries and new mathematical structures that are completely invisible in the standard approach of Lagrangians and Feynman diagrams. Inspired by these developments, the bootstrap philosophy has recently been applied to cosmology. In this talk, I will describe our work on the bootstrapping of cosmological correlations.
The talk will have two parts: In the first part, I will describe the conceptual foundations of the "cosmological bootstrap" as developed together with Arkani-Hamed, Lee and Pimentel in [arXiv:1811.00024]. In the second part, I will describe the extension of these ideas to massless particles with spin, where locality provides important new constraints. This is work to appear with Duaso Pueyo, Joyce, Lee and Pimentel. ––- Contact the organisers (Antoine Bourget and Edoardo Vescovi) for the link.
The past decade has seen an explosion of progress in our understanding of scattering amplitudes in gauge theory and gravity. New bootstrap methods have revealed hidden symmetries and new mathematical structures that are completely invisible in the standard approach of Lagrangians and Feynman diagrams. Inspired by these developments, the bootstrap philosophy has recently been applied to cosmology. In this talk, I will describe our work on the bootstrapping of cosmological correlations.
The talk will have two parts: In the first part, I will describe the conceptual foundations of the "cosmological bootstrap" as developed together with Arkani-Hamed, Lee and Pimentel in [arXiv:1811.00024]. In the second part, I will describe the extension of these ideas to massless particles with spin, where locality provides important new constraints. This is work to appear with Duaso Pueyo, Joyce, Lee and Pimentel. ––- Contact the organisers (Antoine Bourget and Edoardo Vescovi) for the link.
Posted by: IC
Thu
23 Apr 2020
Exact results with defects: an overview
Lorenzo Bianchi
(QMUL)
Abstract:
I will give a summary of recent progress in the computation of exact results in the presence of superconformal defects, focusing on a special class of defect correlators. Along the way, I will comment on the possibility of using integrability and propose various future directions.
NOTE: to receive the link please fill the registration form at integrability-london.weebly.com
I will give a summary of recent progress in the computation of exact results in the presence of superconformal defects, focusing on a special class of defect correlators. Along the way, I will comment on the possibility of using integrability and propose various future directions.
NOTE: to receive the link please fill the registration form at integrability-london.weebly.com
Posted by: andrea
Thu
23 Apr 2020
De Sitter horizons and holographic bulk reconstruction (please email p.agarwal AT qmul.ac.uk for a link to the zoom meeting))
Damian Galante
(King's College)
Abstract:
Cosmological (or de Sitter) horizons behave qualitatively different to black hole horizons and this poses a challenging problem in the context of holography. In this talk, I will discuss a novel construction to probe de Sitter horizons using the usual tools of the AdS/CFT correspondence. I will further explore ongoing efforts to reconstruct the bulk metric in two dimensions from the dual quantum mechanical correlators in the boundary.
Cosmological (or de Sitter) horizons behave qualitatively different to black hole horizons and this poses a challenging problem in the context of holography. In this talk, I will discuss a novel construction to probe de Sitter horizons using the usual tools of the AdS/CFT correspondence. I will further explore ongoing efforts to reconstruct the bulk metric in two dimensions from the dual quantum mechanical correlators in the boundary.
Posted by: QMW
Wed
22 Apr 2020
A status report on the island formula from the perspective of 2d CFT at large central charge
Tarek Anous
(University of Amsterdam)
Abstract:
I will give an informal review of some of the recent developments on reproducing the page curve in semi-classical gravity. I will then compare and contrast these results to older results from the study of holographic 2d CFT with sparse spectra and large central charge. In these quantum systems, there is a natural understanding of the CFT duals of the bulk semiclassical classical saddles that are responsible for evading information loss. I will end with some cautionary remarks explaining why I believe it is too early to declare the information problem "solved". For Zoom link please contact damian.galante at kcl.ac.uk
I will give an informal review of some of the recent developments on reproducing the page curve in semi-classical gravity. I will then compare and contrast these results to older results from the study of holographic 2d CFT with sparse spectra and large central charge. In these quantum systems, there is a natural understanding of the CFT duals of the bulk semiclassical classical saddles that are responsible for evading information loss. I will end with some cautionary remarks explaining why I believe it is too early to declare the information problem "solved". For Zoom link please contact damian.galante at kcl.ac.uk
Posted by: andrea
Thu
16 Apr 2020
A review of the AdS/CFT Quantum Spectral Curve
Fedor Levkovich-Maslyuk
(ENS Paris)
Abstract:
I will give an introduction to the Quantum Spectral Curve in AdS/CFT. This is an integrability-based framework which provides the exact spectrum of planar N = 4 super Yang-Mills theory (and of the dual string model) in terms of a solution of a Riemann-Hilbert problem for a finite set of functions. I review the underlying QQ-relations starting from simple spin chain examples, and describe the special features arising for AdS/CFT. I will also present some pedagogical examples to show the framework in action. Lastly I will briefly discuss its recent applications for correlation functions. Based on the review arXiv:1911.13065.
NOTE: online seminar using Zoom. Please register to the mailing list on integrability-london.weebly.com to participate.
I will give an introduction to the Quantum Spectral Curve in AdS/CFT. This is an integrability-based framework which provides the exact spectrum of planar N = 4 super Yang-Mills theory (and of the dual string model) in terms of a solution of a Riemann-Hilbert problem for a finite set of functions. I review the underlying QQ-relations starting from simple spin chain examples, and describe the special features arising for AdS/CFT. I will also present some pedagogical examples to show the framework in action. Lastly I will briefly discuss its recent applications for correlation functions. Based on the review arXiv:1911.13065.
NOTE: online seminar using Zoom. Please register to the mailing list on integrability-london.weebly.com to participate.
Posted by: andrea
Thu
16 Apr 2020
5d SCFTs and BPS quivers (Please email p.agarwal AT qmul.ac.uk for the zoom link to the meeting)
Cyril Closset
(Oxford)
Abstract:
I will explore aspects of the Coulomb-branch physics of five-dimensional superconformal field theories (SCFT). More precisely, I will consider the 5d SCFT on a circle, and describe the general structure of the Coulomb-branch BPS states as encoded in a "5d BPS quiver," which can be computed from standard string-theory geometric-engineering techniques. The interplay between 4d and 5d BPS quivers will play a central role in our story.
I will explore aspects of the Coulomb-branch physics of five-dimensional superconformal field theories (SCFT). More precisely, I will consider the 5d SCFT on a circle, and describe the general structure of the Coulomb-branch BPS states as encoded in a "5d BPS quiver," which can be computed from standard string-theory geometric-engineering techniques. The interplay between 4d and 5d BPS quivers will play a central role in our story.
Posted by: QMW
Thu
9 Apr 2020
Integrable sigma models and RG flow
Nat Levine
(Imperial College)
Abstract:
It is often suggested that integrable 2d sigma models should be renormalizable, however this relationship has only previously been checked in the 1-loop approximation. The aim of this work is to understand what happens beyond 1-loop.
We shall pedagogically introduce the lambda- and eta-models, and non-abelian duality. Based on these examples, we confirm that classically integrable sigma models appear to be 2-loop renormalizable if supplemented with a particular choice of finite counterterms, i.e. quantum corrections to the target space geometry. The 2-loop beta-function of the lambda-model is computed, matching the known results for groups and symmetric spaces in the limit when the lambda-model becomes the corresponding non-abelian dual model. This leads to the statement that non-abelian duality commutes with the RG flow beyond 1-loop order.
NOTE: Please register to the mailing list at integrability-london.weebly.com to receive the link for the Zoom meeting.
It is often suggested that integrable 2d sigma models should be renormalizable, however this relationship has only previously been checked in the 1-loop approximation. The aim of this work is to understand what happens beyond 1-loop.
We shall pedagogically introduce the lambda- and eta-models, and non-abelian duality. Based on these examples, we confirm that classically integrable sigma models appear to be 2-loop renormalizable if supplemented with a particular choice of finite counterterms, i.e. quantum corrections to the target space geometry. The 2-loop beta-function of the lambda-model is computed, matching the known results for groups and symmetric spaces in the limit when the lambda-model becomes the corresponding non-abelian dual model. This leads to the statement that non-abelian duality commutes with the RG flow beyond 1-loop order.
NOTE: Please register to the mailing list at integrability-london.weebly.com to receive the link for the Zoom meeting.
Posted by: andrea
Fri
3 Apr 2020
Recovering the spacetime metric from a holographic dual
๐ London
Leonel Quinta Queimada
(King's College London)
Abstract:
I will try to provide an overview of the papers 1605.01070, 1612.00391 and most recently 2003.08409, where progress is made in determining how the bulk metric of a holographic spacetime can be reconstructed purely from boundary data. My focus will be in the results of the first reference 1605.01070, which provides the framework for the other works.
Link to meeting: <a href="https://us04web.zoom.us/j/661181319">here</a>
I will try to provide an overview of the papers 1605.01070, 1612.00391 and most recently 2003.08409, where progress is made in determining how the bulk metric of a holographic spacetime can be reconstructed purely from boundary data. My focus will be in the results of the first reference 1605.01070, which provides the framework for the other works.
Link to meeting: <a href="https://us04web.zoom.us/j/661181319">here</a>
Posted by: andrea
Thu
2 Apr 2020
Bootstrapping 1/2 BPS line defects in N=4 SYM
Carlo Meneghelli
(Oxford)
Abstract:
I will present some results on the 1d Super-Conformal Field Theory (SCFT) living on a 1/2-BPS line defect in a 4d N=4 SCFT. The main realization of this setup being Wilson lines in N=4 Super-Yang-Mills (SYM). After reviewing what the modern numerical bootstrap have to say about this problem I will describe how analytic bootstrap methods can efficiently produce the perturbative expansion at strong coupling in the planar theory.
NOTE: This will be an online seminar using Zoom.
Please register at integrability-london.weebly.com to receive the link
I will present some results on the 1d Super-Conformal Field Theory (SCFT) living on a 1/2-BPS line defect in a 4d N=4 SCFT. The main realization of this setup being Wilson lines in N=4 Super-Yang-Mills (SYM). After reviewing what the modern numerical bootstrap have to say about this problem I will describe how analytic bootstrap methods can efficiently produce the perturbative expansion at strong coupling in the planar theory.
NOTE: This will be an online seminar using Zoom.
Please register at integrability-london.weebly.com to receive the link
Posted by: andrea
March 2020
Tue
31 Mar 2020
TBA
Bernd Schroers
(Heriot Watt)
Fri
27 Mar 2020
Toward an Effective CFT2 from N = 4 Super Yang-Mills and Aspects of Hawking Radiation
๐ London
Alejandro Cabo-Bizet
(KCL)
Abstract:
I will discuss the recent paper 2003.02770 with the title above (by J. Nian and L. Pando Zayas).
Link to meeting: <a href="https://us04web.zoom.us/j/661181319">here</a>
I will discuss the recent paper 2003.02770 with the title above (by J. Nian and L. Pando Zayas).
Link to meeting: <a href="https://us04web.zoom.us/j/661181319">here</a>
Posted by: andrea
Thu
26 Mar 2020
Recent advancements in Separation of Variables for higher rank
Paul Ryan
(Trinity College Dublin)
Abstract:
"I will review recent advancements in the development of the Separation
of Variables (SoV) program for rational higher rank spin chains,
motivated by the recent appearance of SoV-type structures in AdS/CFT. I
will discuss the main approaches for constructing a separated variable
basis which include diagonalising the B-operator and the action of fused
transfer matricies on a suitable vacuum state. I will explain how these
approaches are linked and demonstrate how they can be unified into a
single framework governed by Yangian representation theory. The outcome
is that for any finite-dimensional su(n) spin chain the wave functions
(Bethe vectors) factorise into an ascending product of Slater
determinants in Baxter Q-functions, allowing us to immediately link this
operatorial construction of states with the recently developed
functional approach of computing scalar products and form factors."
NOTE: this will be an online seminar using Zoom. To participate please fill the registration form on integrability-london.weebly.com.
"I will review recent advancements in the development of the Separation
of Variables (SoV) program for rational higher rank spin chains,
motivated by the recent appearance of SoV-type structures in AdS/CFT. I
will discuss the main approaches for constructing a separated variable
basis which include diagonalising the B-operator and the action of fused
transfer matricies on a suitable vacuum state. I will explain how these
approaches are linked and demonstrate how they can be unified into a
single framework governed by Yangian representation theory. The outcome
is that for any finite-dimensional su(n) spin chain the wave functions
(Bethe vectors) factorise into an ascending product of Slater
determinants in Baxter Q-functions, allowing us to immediately link this
operatorial construction of states with the recently developed
functional approach of computing scalar products and form factors."
NOTE: this will be an online seminar using Zoom. To participate please fill the registration form on integrability-london.weebly.com.
Posted by: andrea
Wed
25 Mar 2020
TBA
๐ London
Agnese Bissi
(Uppsala University)
Abstract:
TBA
TBA
Posted by: KCL
Tue
24 Mar 2020
Postponed
Romuald Janik
(Jagielonian)
Mon
23 Mar 2020
TBA
Severin Bunk
(Hamburg University)
Fri
20 Mar 2020
Emergent hydrodynamics in integrable systems
๐ London
Benjamin Doyon
(King's College London)
Abstract:
Join <a href="https://redirect.is/jdnb0h">here</a> (you need Microsoft Teams).
Typical systems of many particles in strong interaction have extremely complex behaviours which are hard to study in detail. But when the system is very large, simplicity resurfaces: typically just a few degrees of freedom are relevant, which follow new, simple laws. Understanding what the emergent behaviours are from the underlying microscopic interactions is one of the foremost problems in modern science. A very powerful set of ideas and tools at our disposal is hydrodynamics. Although the Navier-Stokes and related equations have been studied for a very long time, we are now starting to uncover the full potential of the fundamental principles of hydrodynamics. In particular, in a recent breakthrough it was understood how to apply these principles to quantum and classical integrable models, where infinitely many conserved currents exist, giving ``generalised hydrodynamicsรขโฌย. I will overview the fundamental principles of hydrodynamics and their adaptation to integrable systems, with simple examples such as the quantum Lieb-Liniger model, the classical Toda model, and the soliton gases. I will discuss a recent cold-atom experiment that confirmed generalised hydrodynamics, and, if time permits, show some of the exact results that can be obtained with this formalism, such as exact nonequilibrium steady states and exact asymptotic of correlation functions at large space-time separations.
Join <a href="https://redirect.is/jdnb0h">here</a> (you need Microsoft Teams).
Typical systems of many particles in strong interaction have extremely complex behaviours which are hard to study in detail. But when the system is very large, simplicity resurfaces: typically just a few degrees of freedom are relevant, which follow new, simple laws. Understanding what the emergent behaviours are from the underlying microscopic interactions is one of the foremost problems in modern science. A very powerful set of ideas and tools at our disposal is hydrodynamics. Although the Navier-Stokes and related equations have been studied for a very long time, we are now starting to uncover the full potential of the fundamental principles of hydrodynamics. In particular, in a recent breakthrough it was understood how to apply these principles to quantum and classical integrable models, where infinitely many conserved currents exist, giving ``generalised hydrodynamicsรขโฌย. I will overview the fundamental principles of hydrodynamics and their adaptation to integrable systems, with simple examples such as the quantum Lieb-Liniger model, the classical Toda model, and the soliton gases. I will discuss a recent cold-atom experiment that confirmed generalised hydrodynamics, and, if time permits, show some of the exact results that can be obtained with this formalism, such as exact nonequilibrium steady states and exact asymptotic of correlation functions at large space-time separations.
Posted by: andrea
Thu
19 Mar 2020
TBA for the g-function
Edoardo Vescovi
(Imperial College)
Abstract:
The notion of integrability can be extended to systems with boundaries. In large volume and finite temperature, the free energy of such systems รขโฌโ unlike those periodic รขโฌโ contains a non-extensive piece, called g-function, with many physical interpretations. We present a method [1906.07733] hybrid of [1003.5542, 1007.1148, 1809.05705] to calculate the g-function from the TBA partition function.
NOTE: Thus is an online seminar using Zoom. Please follow the registration link on https://integrability-london.weebly.com/
The notion of integrability can be extended to systems with boundaries. In large volume and finite temperature, the free energy of such systems รขโฌโ unlike those periodic รขโฌโ contains a non-extensive piece, called g-function, with many physical interpretations. We present a method [1906.07733] hybrid of [1003.5542, 1007.1148, 1809.05705] to calculate the g-function from the TBA partition function.
NOTE: Thus is an online seminar using Zoom. Please follow the registration link on https://integrability-london.weebly.com/
Posted by: andrea
Wed
18 Mar 2020
t.b.a.
Takato Yoshimura
(Tokyo Institute of Technology)
Abstract:
––––––––- Part of London Integrability Journal Club. If you are a new participant, please register using the form at integrability-london.weebly.com.
––––––––- Part of London Integrability Journal Club. If you are a new participant, please register using the form at integrability-london.weebly.com.
Posted by: andrea
Tue
17 Mar 2020
Postponed
Marika Taylor
(Southampton)
Thu
12 Mar 2020
Cancelled
Valya Khoze
(Durham University)
Tue
10 Mar 2020
Postponed till next term
Roberto Tateo
(Torino)
Wed
4 Mar 2020
Global symmetry and anomalies in (2+1)D topological quantum field theories
Maissam Barkeshli
(University of Maryland)
Abstract:
Topological quantum field theories, which can be used to model topologically ordered phases of matter in quantum many-body systems, exhibit rich behavior in the presence of global symmetries. In this talk I will present progress over the last few years in understanding (2+1)D TQFTs in the presence of a global symmetry group G. This leads to a new mathematical structure, G-crossed braided tensor categories, that characterizes different possible patterns of symmetry fractionalization for topologically non-trivial particles and the fusion and braiding properties of symmetry defects. Two types of anomalies arise in the discussion: (1) "symmetry localization anomalies," which can also be interpreted as the theory possessing a non-trivial 2-group symmetry, and (2) symmetry fractionalization anomalies, which are equivalent to 't Hooft anomalies of the TQFT. I will describe various methods that have been developed in the past few years to compute these anomalies from the algebraic data that defines the TQFT and the symmetry action.
Topological quantum field theories, which can be used to model topologically ordered phases of matter in quantum many-body systems, exhibit rich behavior in the presence of global symmetries. In this talk I will present progress over the last few years in understanding (2+1)D TQFTs in the presence of a global symmetry group G. This leads to a new mathematical structure, G-crossed braided tensor categories, that characterizes different possible patterns of symmetry fractionalization for topologically non-trivial particles and the fusion and braiding properties of symmetry defects. Two types of anomalies arise in the discussion: (1) "symmetry localization anomalies," which can also be interpreted as the theory possessing a non-trivial 2-group symmetry, and (2) symmetry fractionalization anomalies, which are equivalent to 't Hooft anomalies of the TQFT. I will describe various methods that have been developed in the past few years to compute these anomalies from the algebraic data that defines the TQFT and the symmetry action.
Posted by: QMW
Wed
4 Mar 2020
Replica wormholes and the information paradox
Edgar Shaghoulian
(Cornell University)
Abstract:
The information paradox can be realized in two-dimensional models of gravity. In this setting, we show that the large discrepancy between the von Neumann entropy as calculated by Hawking and the requirement of unitarity is fixed by including new saddles in the gravitational path integral. These saddles arise in the replica method as wormholes connecting different copies of the black hole.
The information paradox can be realized in two-dimensional models of gravity. In this setting, we show that the large discrepancy between the von Neumann entropy as calculated by Hawking and the requirement of unitarity is fixed by including new saddles in the gravitational path integral. These saddles arise in the replica method as wormholes connecting different copies of the black hole.
Posted by: QMW
Tue
3 Mar 2020
W-algebras and Yangians
Tomas Prochazka
(LMU Munich)
Abstract:
I will discuss the connection between W-algebras, the higher spin generalizations of the Virasoro algebra which are the symmetry algebras in the 2-dimensional conformal field theory, and Tsymbaliuk's affine Yangian. The bridge between these two algebraic structures is the Miura operator which on one hand provides free field representations of W-algebras and on the other hand satisfies the RTT equations with Maulik-Okounkov R-matrix. The associated integrable structure allows one to easily reproduce many well-known results in conformal field theory.
I will discuss the connection between W-algebras, the higher spin generalizations of the Virasoro algebra which are the symmetry algebras in the 2-dimensional conformal field theory, and Tsymbaliuk's affine Yangian. The bridge between these two algebraic structures is the Miura operator which on one hand provides free field representations of W-algebras and on the other hand satisfies the RTT equations with Maulik-Okounkov R-matrix. The associated integrable structure allows one to easily reproduce many well-known results in conformal field theory.
Posted by: bogdan
February 2020
Thu
27 Feb 2020
Holographic Uhlmann Holonomy and the Entanglement Wedge Symplectic Form
Josh Kirklin
(University of Cambridge)
Abstract:
Subregion duality is an idea in holography which states that every subregion of the boundary theory has a corresponding subregion in the bulk theory, called the 'entanglement wedge', to which it is dual. In the classical limit of the gravity theory, we expect the fields in the entanglement wedge to permit a Hamiltonian description involving a phase space and Poisson brackets. In this talk, I will describe how this phase space arises from the point of view of the boundary theory. In particular, I will explain how it emerges from measurements of a certain quantum information-theoretic quantity, known as the 'Uhlmann phase', in the boundary subregion.
Subregion duality is an idea in holography which states that every subregion of the boundary theory has a corresponding subregion in the bulk theory, called the 'entanglement wedge', to which it is dual. In the classical limit of the gravity theory, we expect the fields in the entanglement wedge to permit a Hamiltonian description involving a phase space and Poisson brackets. In this talk, I will describe how this phase space arises from the point of view of the boundary theory. In particular, I will explain how it emerges from measurements of a certain quantum information-theoretic quantity, known as the 'Uhlmann phase', in the boundary subregion.
Posted by: QMW
Wed
26 Feb 2020
Graduate Lectures: Black Holes in AdS/CFT
Seok Kim
(Seoul National University)
Abstract:
Cardy limit and large black holes; comments on generalizations and other examples
Cardy limit and large black holes; comments on generalizations and other examples
Posted by: QMW
Wed
26 Feb 2020
Color Confinement, Bose-Einstein Condensation and Holographic Emergent Space
๐ London
Masanori Hanada
(Southampton U.)
Abstract:
We propose a unified description of two important phenomena: color confinement in large-\(N\) gauge theory, and Bose-Einstein condensation (BEC). The key lies in relating standard criteria, based on off-diagonal long range order (ODLRO) for BEC and the Polyakov loop for gauge theory: the constant offset of the distribution of the phases of the Polyakov loop corresponds to ODLRO. Indistinguishability associated with the symmetry group –- SU(N) or O(N) in gauge theory, and S_N permutations in the system of identical bosons –- is crucial in either case. This viewpoint may have implications for confinement at finite N, and for quantum gravity via gauge/gravity duality. As a byproduct, we obtain a characterization of the partially-confined/partially-deconfined phase at finite coupling: the constant offset of the distribution of the phases of the Polyakov loop is the order parameter.
We propose a unified description of two important phenomena: color confinement in large-\(N\) gauge theory, and Bose-Einstein condensation (BEC). The key lies in relating standard criteria, based on off-diagonal long range order (ODLRO) for BEC and the Polyakov loop for gauge theory: the constant offset of the distribution of the phases of the Polyakov loop corresponds to ODLRO. Indistinguishability associated with the symmetry group –- SU(N) or O(N) in gauge theory, and S_N permutations in the system of identical bosons –- is crucial in either case. This viewpoint may have implications for confinement at finite N, and for quantum gravity via gauge/gravity duality. As a byproduct, we obtain a characterization of the partially-confined/partially-deconfined phase at finite coupling: the constant offset of the distribution of the phases of the Polyakov loop is the order parameter.
Posted by: KCL
Tue
25 Feb 2020
Graduate Lectures: Black Holes in AdS/CFT
Seok Kim
(Seoul National University)
Abstract:
Indices and protected spectrum
Indices and protected spectrum
Posted by: QMW
Fri
21 Feb 2020
Graduate Lectures: Black Holes in AdS/CFT
Seok Kim
(Seoul National University)
Abstract:
Introduction: black hole thermodynamics; black holes in AdS; holographic viewpoint from (N=4 super) Yang-Mills
Introduction: black hole thermodynamics; black holes in AdS; holographic viewpoint from (N=4 super) Yang-Mills
Posted by: QMW
Thu
20 Feb 2020
AdS black holes and deconfinement
Seok Kim
(Seoul National University)
Abstract:
I will explain the physics of BPS black holes in AdS/CFT in 4 and 3 dimensions, focussing on the deconfined phases of the field theories.
I will explain the physics of BPS black holes in AdS/CFT in 4 and 3 dimensions, focussing on the deconfined phases of the field theories.
Posted by: QMW
Wed
19 Feb 2020
Polygon Seminar KCL: Symmetries and energy in general relativity
๐ London
Mahdi Godazgar
(QMUL)
Abstract:
I will review the relation between symmetries and charges and explain how this works in the context of gravity. I will then explain how dual charges can be derived from a similar procedure.
I will review the relation between symmetries and charges and explain how this works in the context of gravity. I will then explain how dual charges can be derived from a similar procedure.
Posted by: oxford
Wed
19 Feb 2020
t.b.a.
Volker Schomerus
(Desy)
Abstract:
t.b.a. –––- Part of the London Integrability Journal Club. If you are not already registered, please sign up at integrability-london.weebly.com/registration.html. The link will be emailed.
t.b.a. –––- Part of the London Integrability Journal Club. If you are not already registered, please sign up at integrability-london.weebly.com/registration.html. The link will be emailed.
Posted by: andrea
Tue
18 Feb 2020
Some impractical practicalities of the SMEFT
Michael Trott
(Niels Bohr Institute)
Abstract:
In recent years the use of effective field theory techniques has come to the fore when studyingรย the LHC data set. This approach constrains the possible effects of physics beyond the Standard Model, by constraining small modifications of Standard Model interactions in a theory known as the Standard Model Effective Field Theory. Although highly practical and agnostic, the presence of a Higgs field that takes on a background expectation value leads to some unique challenges in formulating this
effective field theory and interfacing the SMEFT with the data. We will review some of the successes of this approach and some of the problems that have appeared. A growing understanding of the physics of the SMEFT as emerging from the geometry of Higgs field space offers great potential to tackle some of the remaining challenges. We will also introduce and discuss this approach.
In recent years the use of effective field theory techniques has come to the fore when studyingรย the LHC data set. This approach constrains the possible effects of physics beyond the Standard Model, by constraining small modifications of Standard Model interactions in a theory known as the Standard Model Effective Field Theory. Although highly practical and agnostic, the presence of a Higgs field that takes on a background expectation value leads to some unique challenges in formulating this
effective field theory and interfacing the SMEFT with the data. We will review some of the successes of this approach and some of the problems that have appeared. A growing understanding of the physics of the SMEFT as emerging from the geometry of Higgs field space offers great potential to tackle some of the remaining challenges. We will also introduce and discuss this approach.
Posted by: IC
Tue
18 Feb 2020
TBA
Jose Edelstein
(Santiago de Compostela)
Mon
17 Feb 2020
Complete 1st post-Minkowskian potential from scattering amplitudes
Sangmin Lee
(Seoul National University)
Abstract:
Building upon recent progress in applying amplitude techniques to perturbative general relativity, we propose a closed-form formula for the conservative Hamiltonian of a spinning binary system at the 1st post-Minkowskian order. It is applicable for general spinning bodies with arbitrary spin multipole moments. It is linear in gravitational constant by definition, but exact to all orders in momentum and spin expansions. At each spin order, our formula implies that the spin-dependence and momentum dependence factorize completely. We compare our formula to a similar one derived in 2017 from a spinning test-body near a Kerr black hole and find perfect agreement.
Building upon recent progress in applying amplitude techniques to perturbative general relativity, we propose a closed-form formula for the conservative Hamiltonian of a spinning binary system at the 1st post-Minkowskian order. It is applicable for general spinning bodies with arbitrary spin multipole moments. It is linear in gravitational constant by definition, but exact to all orders in momentum and spin expansions. At each spin order, our formula implies that the spin-dependence and momentum dependence factorize completely. We compare our formula to a similar one derived in 2017 from a spinning test-body near a Kerr black hole and find perfect agreement.
Posted by: QMW
Thu
13 Feb 2020
O(d,d) covariant string cosmology to all orders in alpha'
Guilherme Franzmann
(NORDITA)
Abstract:
Recently, all duality invariant รยฑรขโฌยฒ (alpha-prime)-corrections to the massless NS-NS sector of string theory on time-dependent backgrounds were classified and the form of their contribution to the action were calculated. In this talk we will see how to introduce matter sources in the resulting equations of motion in an O(d,d) covariant way. Then we show that either starting with the corrected equations and sourcing them with matter or considering corrections to the matter sourced lowest order equations give the same set of equations that defines string cosmology to all orders in รยฑรขโฌยฒ. We also discuss perturbative and non-perturbative de Sitter solutions including matter, and explicitly show that de Sitter solutions are allowed non-perturbatively.
Recently, all duality invariant รยฑรขโฌยฒ (alpha-prime)-corrections to the massless NS-NS sector of string theory on time-dependent backgrounds were classified and the form of their contribution to the action were calculated. In this talk we will see how to introduce matter sources in the resulting equations of motion in an O(d,d) covariant way. Then we show that either starting with the corrected equations and sourcing them with matter or considering corrections to the matter sourced lowest order equations give the same set of equations that defines string cosmology to all orders in รยฑรขโฌยฒ. We also discuss perturbative and non-perturbative de Sitter solutions including matter, and explicitly show that de Sitter solutions are allowed non-perturbatively.
Posted by: QMW
Wed
12 Feb 2020
Amplitudes meet Cosmology
๐ London
Paolo Benincasa
(NBI)
Abstract:
The principles of Lorentz invariance, locality and unitarity highly
constrain the physics at accessible high energy: the type of
interactions allowed as well as most of the theorems known in particle
physics are instances of these principles. This is neatly seen in the
structure of scattering amplitudes in asymptotically flat space-times.
However, cosmology suggests that such principles may be just
approximate: Lorentz invariance is broken at cosmological scales and the
accelerated expansion of the universe seems to prevent a full-fledge
definition of quantum mechanical observables. If our fundamental ideas
in particle physics become somehow approximate in cosmology, what are
the fundamental rules governing cosmological processes?
In this talk I will report on a recent program which aims to address
this question, by bringing both philosophy and methods which have been
successful for scattering amplitudes to the analysis of cosmological
observables. In particular we investigate the analytic properties of the
perturbative wavefunction of the universe, how fundamental physics
is encoded into it, how the flat-space physics reflects into it, and how
all these features are encoded into new mathematical structures, which
can be used as a novel first principle definition of the perturbative
wavefunction.
The principles of Lorentz invariance, locality and unitarity highly
constrain the physics at accessible high energy: the type of
interactions allowed as well as most of the theorems known in particle
physics are instances of these principles. This is neatly seen in the
structure of scattering amplitudes in asymptotically flat space-times.
However, cosmology suggests that such principles may be just
approximate: Lorentz invariance is broken at cosmological scales and the
accelerated expansion of the universe seems to prevent a full-fledge
definition of quantum mechanical observables. If our fundamental ideas
in particle physics become somehow approximate in cosmology, what are
the fundamental rules governing cosmological processes?
In this talk I will report on a recent program which aims to address
this question, by bringing both philosophy and methods which have been
successful for scattering amplitudes to the analysis of cosmological
observables. In particular we investigate the analytic properties of the
perturbative wavefunction of the universe, how fundamental physics
is encoded into it, how the flat-space physics reflects into it, and how
all these features are encoded into new mathematical structures, which
can be used as a novel first principle definition of the perturbative
wavefunction.
Posted by: KCL
Wed
12 Feb 2020
TBA
Evgeny Sobko
(Southampton)
Abstract:
TBA
TBA
Posted by: IC
Tue
11 Feb 2020
Learning about the Planck scale: Marginal couplings and the predictive power of scale invariance
Aaron Held
(Imperial College London)
Abstract:
I will review the current status of the asymptotic safety program,
focusing on the predictive power of scale invariance, followed by a
collection of results on how the Standard-Model couplings may be used to
constrain physics at the Planck scale. At a time in which collider
measurements collect increasing evidence that the Standard Model as an
effective field theory is consistent up to the Planck scale, its
marginal couplings offer a unique opportunity to learn about quantum
gravity.
I will also briefly introduce a research program aimed at constraining
the marginal couplings of the gravitational sector, i.e.,
curvature-squared terms, via black-hole stability and binary mergers.
I will review the current status of the asymptotic safety program,
focusing on the predictive power of scale invariance, followed by a
collection of results on how the Standard-Model couplings may be used to
constrain physics at the Planck scale. At a time in which collider
measurements collect increasing evidence that the Standard Model as an
effective field theory is consistent up to the Planck scale, its
marginal couplings offer a unique opportunity to learn about quantum
gravity.
I will also briefly introduce a research program aimed at constraining
the marginal couplings of the gravitational sector, i.e.,
curvature-squared terms, via black-hole stability and binary mergers.
Posted by: IC
Thu
6 Feb 2020
Towards Structure Constants in N=4 SYM via Quantum Spectral Curve
Fedor Levkovich-Maslyuk
(Ecole Normale Superieure, Paris)
Abstract:
The Quantum Spectral Curve (QSC) is a powerful integrability-based framework capturing the exact spectrum of planar N=4 SYM. We present first evidence that it should also play an important role for computing exact correlation functions. We compute the correlator of 3 scalar local operators connected by Wilson lines forming a triangle in the ladders limit, and show that it massively simplifies when written in terms of the QSC. The final all-loop result takes a very compact form, suggesting its interpretation via Sklyanin's separation of variables (SoV). We discuss work in progress on extending these results to local operators. We also derive, for the first time, the SoV scalar product measure for gl(N) compact and noncompact spin chains.
Based on arXiv:1910.13442, 1907.03788, 1802.0423.
The Quantum Spectral Curve (QSC) is a powerful integrability-based framework capturing the exact spectrum of planar N=4 SYM. We present first evidence that it should also play an important role for computing exact correlation functions. We compute the correlator of 3 scalar local operators connected by Wilson lines forming a triangle in the ladders limit, and show that it massively simplifies when written in terms of the QSC. The final all-loop result takes a very compact form, suggesting its interpretation via Sklyanin's separation of variables (SoV). We discuss work in progress on extending these results to local operators. We also derive, for the first time, the SoV scalar product measure for gl(N) compact and noncompact spin chains.
Based on arXiv:1910.13442, 1907.03788, 1802.0423.
Posted by: IC
Wed
5 Feb 2020
D-instantons and the non-perturbative completion of c=1 string theory
Xi Yin
(Harvard)
Abstract:
I will discuss a systematic way of taking into account non-perturbative effects on the closed string scattering amplitudes in c=1 string theory, and present a recent proposal on the corresponding non-perturbative completion of the dual matrix quantum mechanics.
I will discuss a systematic way of taking into account non-perturbative effects on the closed string scattering amplitudes in c=1 string theory, and present a recent proposal on the corresponding non-perturbative completion of the dual matrix quantum mechanics.
Posted by: bogdan
Wed
5 Feb 2020
Revisiting long strings in c=1 string theory
Xi Yin
(Harvard)
Abstract:
I will discuss FZZT branes and long strings in c=1 string theory, and the dual description of the latter in non-singlet sectors of the matrix quantum mechanics. I will present highly nontrivial evidences for the duality at the level of perturbative scattering amplitudes, and discuss implications on black holes in c=1 string theory and their matrix model duals.
I will discuss FZZT branes and long strings in c=1 string theory, and the dual description of the latter in non-singlet sectors of the matrix quantum mechanics. I will present highly nontrivial evidences for the duality at the level of perturbative scattering amplitudes, and discuss implications on black holes in c=1 string theory and their matrix model duals.
Posted by: bogdan
Tue
4 Feb 2020
CFTs at Large Charge
Susanne Reffert
(University of Bern)
Abstract:
The large-charge approach consists in studying conformal field theories in sectors of fixed and large global charge. This allows performing a perturbative expansion of a generically strongly-coupled theory with the inverse charge acting as a controlling parameter. In this talk, I will present the basic idea of the large-charge expansion using the simplest example of the 3D O(2) model at the Wilson-Fisher fixed point, as well as its application to other models.
The large-charge approach consists in studying conformal field theories in sectors of fixed and large global charge. This allows performing a perturbative expansion of a generically strongly-coupled theory with the inverse charge acting as a controlling parameter. In this talk, I will present the basic idea of the large-charge expansion using the simplest example of the 3D O(2) model at the Wilson-Fisher fixed point, as well as its application to other models.
Posted by: IC
Tue
4 Feb 2020
Stochastic modeling of diffusion in dynamical systems: three examples
Rainer Klages
(QMUL)
Abstract:
Consider equations of motion yielding dispersion of an ensemble of particles. For
a given dynamical system an interesting problem is not only what type of diffusion
is generated but also whether the resulting diffusive dynamics matches to a known
stochastic process. I will discuss three examples of dynamical systems displaying
different types of diffusive transport: The first model is fully deterministic but nonchaotic
by showing a whole range of normal and anomalous diffusion under variation
of a single control parameter [1]. The second model is a soft Lorentz gas where a point
particles moves through repulsive Fermi potentials situated on a triangular periodic
lattice [2]. It is fully deterministic by displaying an intricate switching between
normal and superdiffusion under variation of control parameters. The third model
randomly mixes in time chaotic dynamics generating normal diffusive spreading with
non-chaotic motion where all particles localize [3]. Varying a control parameter the
mixed system exhibits a transition characterised by subdiffusion. In all three cases
I will show successes, failures and pitfalls if one tries to reproduce the resulting
diffusive dynamics by using simple stochastic models.
Joint work with all authors on the references cited below.
[1] L. Salari, L. Rondoni, C. Giberti, R. Klages, Chaos 25, 073113 (2015)
[2] R.Klages, S.S.Gallegos, J.Solanpรยจaรยจa, M.Sarvilahti, Phys. Rev. Lett. 122, 064102
(2019)
[3] Y.Sato, R.Klages, Phys. Rev. Lett. 122, 174101 (2019)
Consider equations of motion yielding dispersion of an ensemble of particles. For
a given dynamical system an interesting problem is not only what type of diffusion
is generated but also whether the resulting diffusive dynamics matches to a known
stochastic process. I will discuss three examples of dynamical systems displaying
different types of diffusive transport: The first model is fully deterministic but nonchaotic
by showing a whole range of normal and anomalous diffusion under variation
of a single control parameter [1]. The second model is a soft Lorentz gas where a point
particles moves through repulsive Fermi potentials situated on a triangular periodic
lattice [2]. It is fully deterministic by displaying an intricate switching between
normal and superdiffusion under variation of control parameters. The third model
randomly mixes in time chaotic dynamics generating normal diffusive spreading with
non-chaotic motion where all particles localize [3]. Varying a control parameter the
mixed system exhibits a transition characterised by subdiffusion. In all three cases
I will show successes, failures and pitfalls if one tries to reproduce the resulting
diffusive dynamics by using simple stochastic models.
Joint work with all authors on the references cited below.
[1] L. Salari, L. Rondoni, C. Giberti, R. Klages, Chaos 25, 073113 (2015)
[2] R.Klages, S.S.Gallegos, J.Solanpรยจaรยจa, M.Sarvilahti, Phys. Rev. Lett. 122, 064102
(2019)
[3] Y.Sato, R.Klages, Phys. Rev. Lett. 122, 174101 (2019)
Posted by: CityU2
January 2020
Thu
30 Jan 2020
Non-Hermitian extension of the Standard Model
Jean Alexandre
(King's College)
Abstract:
The work presented here explores the possibility of introducing non-Hermitian scalar and fermion mass terms, in addition to the usual Hermitian ones. The consistency of the resulting description requires a reworking of all the fundamental properties in Field Theory from the beginning, which is challenging but appears to be possible.
The work presented here explores the possibility of introducing non-Hermitian scalar and fermion mass terms, in addition to the usual Hermitian ones. The consistency of the resulting description requires a reworking of all the fundamental properties in Field Theory from the beginning, which is challenging but appears to be possible.
Posted by: QMW
Thu
30 Jan 2020
TBA
Konstantinos Sfetsos
(University of Athens)
Abstract:
TBA
TBA
Posted by: IC
Wed
29 Jan 2020
The O(N) S-matrix monolith
๐ London
Lucia Cordova
(ENS, Paris)
Abstract:
In this talk I will explore the space of two-to-two S-matrices in two-dimensional theories with a global O(N) symmetry, as restricted by the general principles of unitarity, crossing and analyticity. I will describe various features of the allowed space and identify some special points on its boundary with known integrable theories. Finally, I will present a useful dual formulation of the S-matrix bootstrap problem. Based on arXiv:1909.06495.
In this talk I will explore the space of two-to-two S-matrices in two-dimensional theories with a global O(N) symmetry, as restricted by the general principles of unitarity, crossing and analyticity. I will describe various features of the allowed space and identify some special points on its boundary with known integrable theories. Finally, I will present a useful dual formulation of the S-matrix bootstrap problem. Based on arXiv:1909.06495.
Posted by: KCL
Tue
28 Jan 2020
Table-top Testing of the Non-Classicality of Gravity: A Proposal and its Assumptions, Implications and Practicalities
Sougato Bose
(University College London)
Abstract:
A lack of empirical evidence has lead to a debate on whether gravity is a quantum entity. Motivated by this, I will present a feasible idea for such a test based on the principle that two objects cannot be entangled without a quantum mediator. I will show that despite the weakness of gravity, the phase evolution induced by the gravitational interaction of two micron size test masses in adjacent matter-wave interferometers can detectably entangle them even when they are placed far apart enough to keep Casimir-Polder forces at bay. A prescription for witnessing this entanglement, which certifies gravity as a quantum coherent mediator, is also provided and can be measured through simple spin correlations. Further, I clarify the assumptions underpinning the above proposal such as our reasonable definition of "classicality", as well as the crucial aspect of the locality of physical interactions. The role of off-shell processes is also highlighted. How the experiment sits within relativistic quantum field theory is clarified. Lastly, the practical challenges are noted. Time permitting other applications of superpositions of nano-crystals, such as in sensing classical gravity and how to detect nonclassicalities of such crystals without preparing superpositions at first, will be discussed.
A lack of empirical evidence has lead to a debate on whether gravity is a quantum entity. Motivated by this, I will present a feasible idea for such a test based on the principle that two objects cannot be entangled without a quantum mediator. I will show that despite the weakness of gravity, the phase evolution induced by the gravitational interaction of two micron size test masses in adjacent matter-wave interferometers can detectably entangle them even when they are placed far apart enough to keep Casimir-Polder forces at bay. A prescription for witnessing this entanglement, which certifies gravity as a quantum coherent mediator, is also provided and can be measured through simple spin correlations. Further, I clarify the assumptions underpinning the above proposal such as our reasonable definition of "classicality", as well as the crucial aspect of the locality of physical interactions. The role of off-shell processes is also highlighted. How the experiment sits within relativistic quantum field theory is clarified. Lastly, the practical challenges are noted. Time permitting other applications of superpositions of nano-crystals, such as in sensing classical gravity and how to detect nonclassicalities of such crystals without preparing superpositions at first, will be discussed.
Posted by: IC
Tue
28 Jan 2020
TBA
Jacopo de Nardis
(Ghent)
Thu
23 Jan 2020
Surface defects in 4d superconformal theories and chiral algebras
Madalena Lemos
(CERN)
Abstract:
We study symmetry constraints on BPS surface defects in four-dimensional superconformal field theories, showing how supersymmetry imposes relations on anomaly coefficients. Turning to dynamics, we analyze a protected subsector of N=(2,2) surface defects that is captured by a two-dimensional chiral algebra. We discuss how to compute observables of interacting defects from the chiral algebra, including the aforementioned anomaly coefficients.
We study symmetry constraints on BPS surface defects in four-dimensional superconformal field theories, showing how supersymmetry imposes relations on anomaly coefficients. Turning to dynamics, we analyze a protected subsector of N=(2,2) surface defects that is captured by a two-dimensional chiral algebra. We discuss how to compute observables of interacting defects from the chiral algebra, including the aforementioned anomaly coefficients.
Posted by: QMW
Wed
22 Jan 2020
Five-Point Functions in N=4 SYM
๐ London
Thiago Fleury
(International Institute of Physics UFRN)
Abstract:
The correlation functions (three and higher point) in N=4 SYM can be computed using integrability techniques.
One formalism is called hexagonalization and its main object is an integrable form-factor with hexagonal shape.
It was successfully used to compute a specific all loop four-point function for the first time.
However, it seems that new developments are needed to understand the five-point function and other kinds
of finite size corrections. In this talk, after a long review of the hexagonalization procedure, I will explain
the five-point calculation at weak coupling and its difficulties.
The correlation functions (three and higher point) in N=4 SYM can be computed using integrability techniques.
One formalism is called hexagonalization and its main object is an integrable form-factor with hexagonal shape.
It was successfully used to compute a specific all loop four-point function for the first time.
However, it seems that new developments are needed to understand the five-point function and other kinds
of finite size corrections. In this talk, after a long review of the hexagonalization procedure, I will explain
the five-point calculation at weak coupling and its difficulties.
Posted by: KCL
Wed
22 Jan 2020
TBA
Sergey Frolov
(Trinity College Dublin)
Abstract:
TBA
TBA
Posted by: IC
Tue
21 Jan 2020
A proposal for the CFT dual for superstrings on ADS3 at the string radius
Massimo Porrati
(New York University)
Abstract:
After a review of the spectrum of superstrings on the AdS3 WZW background, I will use a conjecture positing the existence of a phase transition, when the AdS radius becomes of order of the string length, to propose a holographic dual CFT that matches exactly the entire continuous spectrum of the superstring. I will conclude with a few observations on the role of interactions amd discrete, short-string states.
After a review of the spectrum of superstrings on the AdS3 WZW background, I will use a conjecture positing the existence of a phase transition, when the AdS radius becomes of order of the string length, to propose a holographic dual CFT that matches exactly the entire continuous spectrum of the superstring. I will conclude with a few observations on the role of interactions amd discrete, short-string states.
Posted by: IC
Tue
21 Jan 2020
Differential operators for superconformal correlation functions
Andrea Manenti
(EPFL)
Abstract:
I present a method to expand in components four dimensional superconformal multiplets in N=1 and N=2 superconformal field theories. The method consists in constructing a differential operator for each descendant, which can then be applied on any correlator in superspace. In particular I show how the action on three-point functions can be considerably simplified. An interesting application of the formalism is the proof that N=2 spinning chiral primaries (also called รขโฌหexoticรขโฌโข primaries) cannot exist in any local SCFT. The interest in constraining this particular kind of operator stemmed from a result in the literature that ruled them out from a very large class of theories. I also discuss the role of the differential operators in the computation of superconformal blocks.
I present a method to expand in components four dimensional superconformal multiplets in N=1 and N=2 superconformal field theories. The method consists in constructing a differential operator for each descendant, which can then be applied on any correlator in superspace. In particular I show how the action on three-point functions can be considerably simplified. An interesting application of the formalism is the proof that N=2 spinning chiral primaries (also called รขโฌหexoticรขโฌโข primaries) cannot exist in any local SCFT. The interest in constraining this particular kind of operator stemmed from a result in the literature that ruled them out from a very large class of theories. I also discuss the role of the differential operators in the computation of superconformal blocks.
Posted by: QMW
Tue
21 Jan 2020
TBA
Elli Pomoni
(DESY)
Mon
20 Jan 2020
Emergent diffusion and super-diffusion in quantum and classical chains.
๐ London
Jacopo de Nardis
(University of Ghent)
Abstract:
Finding a theoretical framework to explain how phenomenological transport laws on macroscopic scales emerge from
microscopic deterministic dynamics poses one of the most significant challenges of condensed matter physics.
In recent years, the advent of the generalized hydrodynamics in integrable quantum systems and more recent studies of quantum chaos and its relation to transport, reinvigorated
the field of nonequilibrium physics in spin chains. Numerous results were found: lower bounds to diffusion constants, exact expressions for diffusion coefficients and remarkable anomalous features of transport in quantum and classical chains, deeply related to the Kardar-Parisi-Zhang dynamical universality class.
I will present an overview of such results with a particular focus on anomalous transport and its relation to non-linear hydrodynamics.
Finding a theoretical framework to explain how phenomenological transport laws on macroscopic scales emerge from
microscopic deterministic dynamics poses one of the most significant challenges of condensed matter physics.
In recent years, the advent of the generalized hydrodynamics in integrable quantum systems and more recent studies of quantum chaos and its relation to transport, reinvigorated
the field of nonequilibrium physics in spin chains. Numerous results were found: lower bounds to diffusion constants, exact expressions for diffusion coefficients and remarkable anomalous features of transport in quantum and classical chains, deeply related to the Kardar-Parisi-Zhang dynamical universality class.
I will present an overview of such results with a particular focus on anomalous transport and its relation to non-linear hydrodynamics.
Posted by: KCL
Thu
16 Jan 2020
Exact structure constants of determinant operators
Edoardo Vescovi
(Imperial College London)
Abstract:
In this talk, based on [1906.07733] and [1907.11242] with Y. Jiang and S. Komatsu, we derive the first non-perturbative result for the structure constant of two determinant operators and a non-BPS single-trace operator of finite length in planar N=4 SYM.
First, we introduce an effective theory for such correlators at zero coupling. The form of the result supports the interpretation of the three-point function as an overlap between an integrable boundary state, which we determine using symmetry and integrability, and the state describing the single-trace operator. Second, we use thermodynamic Bethe ansatz to derive a non-perturbative expression for such overlap. Finally, we discuss applications that could be addressed with these methods.
In this talk, based on [1906.07733] and [1907.11242] with Y. Jiang and S. Komatsu, we derive the first non-perturbative result for the structure constant of two determinant operators and a non-BPS single-trace operator of finite length in planar N=4 SYM.
First, we introduce an effective theory for such correlators at zero coupling. The form of the result supports the interpretation of the three-point function as an overlap between an integrable boundary state, which we determine using symmetry and integrability, and the state describing the single-trace operator. Second, we use thermodynamic Bethe ansatz to derive a non-perturbative expression for such overlap. Finally, we discuss applications that could be addressed with these methods.
Posted by: QMW
Wed
15 Jan 2020
TBA
Hynek Paul
(Southampton)
Abstract:
TBA
TBA
Posted by: IC
Tue
14 Jan 2020
Moduli spaces of BPS Wilson loops in 3d and quiver varieties
Nadav Drukker
(King's College London)
Abstract:
In this talk I will reexamine the classification of BPS Wilson loops in 3d super Chern-Simons-matter theories. Over the last several years a large class of increasingly intricate constructions of such operators have been found. They involve both discrete and continuous parameters chosen to satisfy varied conditions. In my talk I will explain that the discrete parameters are related to choosing a graded quiver diagram, which may be a subquiver or a cover of the one defining the theory. The continuous parameters are then a singular limit of the variety, a complex manifold, associated to that quiver.
In this talk I will reexamine the classification of BPS Wilson loops in 3d super Chern-Simons-matter theories. Over the last several years a large class of increasingly intricate constructions of such operators have been found. They involve both discrete and continuous parameters chosen to satisfy varied conditions. In my talk I will explain that the discrete parameters are related to choosing a graded quiver diagram, which may be a subquiver or a cover of the one defining the theory. The continuous parameters are then a singular limit of the variety, a complex manifold, associated to that quiver.
Posted by: IC
Thu
9 Jan 2020
Impossible Theories of Gravity
Brando Bellazzini
(IPHT)
Abstract:
Not every effective theory of fields and gravitational interactions at low energy can be embedded into a consistent theory of gravity at short distances. I will discuss how fundamental properties of scattering amplitudes, such as unitarity and causality of the underlying fundamental theory, can be used to spot inconsistent theories of gravity at low-energy, and hence throw them in the so-called EFT ``swampland'รขโฌโข. I will focus on two main applications: the weak gravity conjecture for the physics of extremal black holes; and modified gravity theories such as Galileons, of interest for late-time cosmology.
Not every effective theory of fields and gravitational interactions at low energy can be embedded into a consistent theory of gravity at short distances. I will discuss how fundamental properties of scattering amplitudes, such as unitarity and causality of the underlying fundamental theory, can be used to spot inconsistent theories of gravity at low-energy, and hence throw them in the so-called EFT ``swampland'รขโฌโข. I will focus on two main applications: the weak gravity conjecture for the physics of extremal black holes; and modified gravity theories such as Galileons, of interest for late-time cosmology.
Posted by: QMW
Wed
8 Jan 2020
TBA
๐ London
Eliezer Rabinovici
(HUJ)
Abstract:
TBA
TBA
Posted by: KCL