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## Seminars at

Found at least 20 result(s)

### 01.03.2021 (Monday)

#### Lonti: From spin chain to AdS/CFT with Mathematica

Regular Seminar Nikolay Gromov (KCL)

 at: 10:30 Otherroom Youtube abstract: The release of the youtube video for the London Theory institute seminar series https://youtu.be/jTRQTwBX9ek. In this introductory lecture we describe the XXX Heisenberg spin chain, study its spectrum, wavefunctions and discuss integrability of the system. Some examples are given with simple Mathematica code. We also discuss applications to AdS/CFT correspondence. Some derivations are formulated in the form of step-by-step exercises. They can be solved either with Mathematica or by hand. A quick introduction to Mathematica is provided in a separate video.

### 25.02.2021 (Thursday)

#### Integrable E-models, 4d Chern-Simons theory and affine Gaudin models

Journal Club Benoit Vicedo (University of York)

 at: 15:15 Otherroom Zoom, instructions in abstract abstract: Two-dimensional integrable field theories are characterised by the existence of infinitely many integrals of motion. Recently, two unifying frameworks for describing such theories have emerged, based on four-dimensional Chern-Simons theory in the presence of surface defects and on Gaudin models associated with affine Kac-Moody algebras. I will explain how these formalisms can be used to construct infinite families of two-dimensional integrable field theories. The latter can all naturally be formulated as so-called E-models, a framework for describing Poisson-Lie T-duality in sigma-models. The talk will be based on the joint work [arXiv:2008.01829] with M. Benini and A. Schenkel and [2011.13809] with S. Lacroix. ---- Please register using the form at integrability-london.weebly.com if you are a new participant. The link will be emailed.

### 18.02.2021 (Thursday)

#### Conformal Fourier Analysis and Gaudin Integrability

Journal Club Volker Schomerus (Desy)

 at: 15:15 Otherroom Zoom, instructions in abstract abstract: Conformal partial wave expansion provide Fourier-like decompositions of correlation functions in Conformal Field Theory. Despite their fundamental importance, conformal partial waves remain poorly understood, at least beyond the case of four local fields. In the last few years, a deep relation with integrable quantum mechanical models has emerged. It offers a wealth of powerful new algebraic methods to study and construct conformal partial waves e.g. for general supermultiplets, non-local (line-, surface-) operators and multi-point correlation functions. In my talk I will use ideas from harmonic analysis of the conformal group to embed conformal partial waves into the framework of Gaudin integrable models and then discuss several concrete ramifications as trigonometric and elliptic Calogero-Sutherland models. The latter are relevant for multi-point blocks of scalar fields. ----- Part of London Integrability Journal Club. Please register at integrability-london.weebly.com/registration.html if you are a new participant.

### 11.02.2021 (Thursday)

#### Modeling finite-entropy states with free fermions

Journal Club Oleksandr Gamayun (University of Amsterdam)

 at: 15:15 Otherroom Zoom, instructions in abstract abstract: The behavior of dynamical correlation functions in one-dimensional quantum systems at zero temperature is now very well understood in terms of linear and non-linear Luttinger models. The "microscopic" justification of these models consists in exactly accounting for the soft-mode excitations around the vacuum state and at most a few high-energy excitations. At finite temperature, or more generically for finite entropy states, this direct approach is not strictly applicable due to the different structure of soft excitations. To address these issues we study the asymptotic behavior of correlation functions in one-dimensional free fermion models. On the one hand, we obtain exact answers in terms of Fredholm determinants. On the other hand, based on "microscopic" numerical resummations, we develop a phenomenological approach that provides results depending only on the state-dependent dressing of the scattering phase. Our main example will be the sine-kernel and correlation functions in XY model. -------------------- Part of the London Integrability Journal Club. New participants please register using the form at integrability-london.weebly.com.

### 04.02.2021 (Thursday)

#### Wilson-'t Hooft lines as transfer matrices

Journal Club Junya Yagi (Tsinghua)

 at: 15:15 Otherroom Zoom, instructions in abstract abstract: Supersymmetric gauge theories in four dimensions have various interrelated connections to quantum integrable systems. I will present a new correspondence which identifies Wilson-'t Hooft lines in N=2 circular quiver theories with transfer matrices of trigonometric systems. I will explain how this correspondence is related to Costello's 4d Chern-Simons theory and other similar correspondences. This is based on my joint work with Kazunobu Maruyoshi and Toshihiro Ota. -------------------- Part of the London Integrability Journal Club. New participants please register using the form at integrability-london.weebly.com.

### 28.01.2021 (Thursday)

#### 2D dilaton-gravity, matrix models, and the minimal string

Journal Club Gustavo Turiaci (UC Santa Barbara)

 at: 15:15 Otherroom Zoom, instructions in abstract abstract: In the first part of this talk I will review the recent realization that a large class of two-dimensional theories of dilaton-gravity in asymptotically AdS space are holographically dual to a random matrix model. In this description the matrix represents a random boundary Hamiltonian, and its probability distribution depends on the dilaton potential in a specific way. In the second part of the talk I will explain the relation between two-dimensional dilaton-gravity and the minimal string theory. -------------------- Part of the London Integrability Journal Club. New participants please register using the form at integrability-london.weebly.com.

### 21.01.2021 (Thursday)

#### Overlaps and Fermionic Dualities for Integrable Super Spin Chains

Journal Club Charlotte Kristjansen (Niels Bohr Institute Copenhagen)

 at: 15:15 Otherroom Zoom, instructions in abstract abstract: The $\mathfrak{psu}(2,2|4)$ integrable super spin chain underlying the AdS/CFT correspondence has integrable boundary states which describe set-ups where $k$ D3-branes get dissolved in a probe D5-brane. Overlaps between Bethe eigenstates and these boundary states encode the one-point functions of conformal operators and are expressed in terms of the superdeterminant of the Gaudin matrix that in turn depends on the Dynkin diagram of the symmetry algebra. The different possible Dynkin diagrams of super Lie algebras are related via fermionic dualities and we determine how overlap formulae transform under these dualities. As an application we show how to consistently move between overlap formulae obtained for $k=1$ from different Dynkin diagrams. -------------------- Part of the London Integrability Journal Club. New participants please register using the form at integrability-london.weebly.com.

### 14.01.2021 (Thursday)

#### Integrability and Braided Tensor Categories

Regular Seminar Paul Fendley (Oxford)

 at: 15:15 Otherroom Zoom, instructions in abstract abstract: Many integrable critical classical statistical mechanical models and the corresponding quantum spin chains possess a fractional-spin conserved current. These currents have been constructed by utilising quantum-group algebras, fermionic and parafermionic operators, and ideas from discrete holomorphicity''. I define them generally and naturally using a braided tensor category, a topological structure familiar from the study of knot invariants, anyons and conformal field theory. Such a current amounts to terminating a lattice topological defect, and I will touch on related work on such done with Aasen and Mong. I show how requiring a current be conserved yields simple constraints on the Boltzmann weights, and that all of the many models known to satisfy these constraints are integrable. This procedure therefore gives a linear construction for Baxterising'', i.e. building a solution of the Yang-Baxter equation out of topological data. -------------------- Part of the London Integrability Journal Club. New participants please register using the form at integrability-london.weebly.com.

### 17.12.2020 (Thursday)

#### Integrability Gong Show

Journal Club seven speakers ()

 at: 15:15 Otherroom Zoom, instructions in abstract abstract: We will have seven 10 mins talks + discussions, with: 1) Sara Bonansea (INFN Florence and NBI) - "Wilson loop correlators in defect N=4 SYM" 2) Andrea Fontanella (Humboldt) - "Lie Algebra Expansion in Coset Sigma Models and Non-relativistic String Theory" 3) Suvajit Majumder (City) - "Protected states in AdS3xS3xT4 from integrability" 4) Gerben Oling (NBI) - "Non-relativistic strings and limits of AdS/CFT" 5) Chiara Paletta (TCD) - "Integrable open quantum systems" 6) Davide Polvara (Durham) - "From tree-level perturbation theory to the S-matrix bootstrap in two dimensions" 7) Anton Pribytok (TCD) - "Deformed AdS Integrability and Free Fermion Condition" ----------------------------------- Part of the London Integrability Journal Club. New participants are required to register using the form at integrability-london.weebly.com. The link will be emailed. Abstracts on the website.

### 10.12.2020 (Thursday)

#### An Operator Product Expansion for Form Factors

Journal Club Matthias Wilhelm (Niels Bohr Institute Copenhagen)

 at: 15:15 Otherroom Zoom, instructions in abstract abstract: In this talk, I discuss an operator product expansion for planar form factors of local operators in N=4 SYM theory. In this expansion, a form factor is decomposed into a sequence of known pentagon transitions and a new universal object - the form factor transition. This transition is subject to a set of non-trivial bootstrap constraints, which can be used to determine it at finite coupling. I demonstrate this for MHV form factors of the chiral half of the stress tensor supermultiplet, which in particular contains the chiral Lagrangian and the 20'. ---- Part of London Integrability Journal Club. If you are a new participant, please register filling the form at integrability-london.weebly.com. The link will be emailed.

### 03.12.2020 (Thursday)

#### Phases of unitary matrix models and lattice QCD in two dimensions

Journal Club Jorge Russo (University of Barcelona)

 at: 15:15 Otherroom Zoom, instructions in abstract abstract: We investigate the different large N phases of a deformed Gross-Witten-Wadia U(N) matrix model. The deformation, which leads to a solvable model, corresponds to the addition of characteristic polynomial insertions and mimicks the one-loop determinant of fermion matter. In one version of the model, the GWW phase transition is smoothed out and it becomes a crossover. In another version, the phase transition occurs along a critical line in the two-dimensional parameter space spanned by the 't~Hooft coupling $\lambda$ and the Veneziano parameter $\tau$. A calculation of the $\beta$ function shows the existence of an IR stable fixed point. ---- Part of London Integrability Journal Club. If you are a new participant, please register filling the form at integrability-london.weebly.com. The link will be emailed.

### 26.11.2020 (Thursday)

#### Integrability Gong Show

Journal Club six speakers ( )

 at: 15:15 Otherroom Zoom, instructions in abstract abstract: This Thursday we will have six speakers presenting a 10 mins talk each. 1) Stefano Baiguera (Niels Bohr Institute), "Non-relativistic near-BPS corners of N=4 super Yang-Mills with SU(1,1) symmetry". 2) Ilija Buric (Desy), "From Integrable Gaudin Models to Multipoint Conformal Blocks", 3) Julius Julius (King's College London), "Baxter Equation for Boundary Integrability", 4) Rob Klabbers (Nordita), "How coordinate Bethe ansatz works for Inozemtsev model", 5) Yuan Miao (University of Amsterdam), "On the Q-operator and the spectrum of the XXZ model at root of unity". 6) Anne Spiering (Trinity College Dublin), "Integrability and Quantum Chaos in N=4 SYM from the Spectral Rigidity". Join us to hear the latest news in integrability! Important: Please make sure your Zoom version is updated, in order to use the break-out rooms feature for discussions after the talks. See the journal club website for abstracts of the talks. ----------------------------- Part of the London Integrability Journal Club. New participants please register using the form which can be found on the webpage integrability-london.weebly.com. The link will be emailed.

### 19.11.2020 (Thursday)

#### Integrable Kondo line defect, 4D Chern Simons, and ODE/IM correspondence

Journal Club Jingxiang Wu (Perimeter Institute)

 at: 15:15 Otherroom Zoom, instructions in abstract abstract: I will discuss the integrability and wall-crossing properties of Kondo line defects in rational conformal field theories. It provides a large class of interesting defect RG flow starting from topological line defects. As a surprise, I will discuss new examples of the ODE/IM correspondence and our attempts towards its physical origin using 4d Chern Simons theory. This work is part of a multi-pronged exploration of studying 4D Chern-Simons theory as an overarching structure for integrable systems. ---- Part of London Integrability Journal Club. New participants can register using the form at integrability-london.weebly.com. The link will be emailed.

### 16.11.2020 (Monday)

#### Witten diagrams and the Mellin transform in AdS/CFT

Journal Club Congkao Wen (QMUL)

 at: 09:00 Otherroom Online abstract: AdS/CFT duality (or more general holographic principle) represents a major advance in understanding quantum gravity, and provides powerful tools for studying strongly coupled quantum field theories. This talk will give a basic introduction to AdS/CFT duality, with the focus on the computation of Witten diagrams and their Mellin transform. Witten diagrams, which play the role of Feynman diagrams, provide the means for computing correlation functions in AdS/CFT. We will show that CFT correlation functions obtained from Witten diagrams have much simpler structures after Mellin transform. Correlators in Mellin space are very analogous to the flat-space scattering amplitudes, and they are often called Mellin amplitudes. We will demonstrate the ideas by studying a few non-trivial examples.

### 14.11.2020 (Saturday)

#### t.b.a.

Regular Seminar Paul Fendley (Oxford)

 at: 15:15 Otherroom Zoom, instructions in abstract abstract: t.b.a. -------------------- Part of the London Integrability Journal Club. New participants please register using the form at integrability-london.weebly.com.

### 12.11.2020 (Thursday)

#### Superintegrable systems on moduli spaces of flat connections

Journal Club Nicolai Reshetikhin (Berkeley)

 at: 15:15 Otherroom Zoom, instructions in abstract abstract: Part of London Integrability Journal Club. New participants should register using the form at integrability-london.weebly.com. The link will be emailed.

### 09.11.2020 (Monday)

#### Branes and the moduli space of instantons

Journal Club Amihay Hanany (Imperial College)

 at: 10:30 Otherroom Online abstract: The first recorded lecture of the London Theory Institute for PhD Students. Link to recording and problems (to be solved in live Zoom session next Monday) as well as registration details at https://lonti.weebly.com/ and https://youtu.be/CGDNipeuVEs Instantons, or solutions to the self dual Yang Mills (SDYM) equations are well known solutions, introduced in the mid 70s and played a role in a host of applications in QFT and String Theory. This talk will show a simple brane construction which allows the computation of the moduli space of solutions to the SDYM equations, introduce the student to the world of quivers, and demonstrate simple computations which allow evaluations of these moduli spaces.

### 05.11.2020 (Thursday)

#### Non-planar N=4 SYM: from integrability to quantum chaos

Journal Club Tristan McLoughlin (Trinity College Dublin)

 at: 15:15 Otherroom Zoom, instructions in abstract abstract: In this talk we will consider the spectrum of anomalous dimensions in N=4 super-Yang-Mills and related theories. We will first discuss the emergence of quantum chaos as one goes from infinite to finite N and how the perturbative spectrum is described by GOE random matrix theory. We will then describe how the integrability of the planar-limit can be used to rewrite the computation of the leading 1/N corrections to the one-loop anomalous dimensions in terms of scalar products of off-shell Bethe states or, alternatively, hexagon-like functions.---- Part of London Integrability Journal Club. If you are a new participant, please register filling the form at integrability-london.weebly.com. The link will be emailed.

### 02.11.2020 (Monday)

#### Global symmetry, Euclidean gravity, and the black hole information problem

Journal Club Daniel Harlow (MIT)

 at: 15:00 Otherroom virtual abstract: Part of the London Black Hole Information Paradox Journal Club (for Zoom link, please subscribe here: https://forms.gle/wLYi4A72tEUwuzGK6)

### 29.10.2020 (Thursday)

#### The TTbar deformation and a promising 4D generalisation

Journal Club Roberto Tateo (University of Torino)

 at: 15:15 Otherroom Zoom, instructions in abstract abstract: Two-dimensional field theories deformed by Zamolodchikov's TTbar operator have recently attracted the attention of theoretical physicists due to the many important links with string theory and AdS/CFT. In this talk, I will describe various classical and quantum aspects of this particular irrelevant perturbation, including its geometrical interpretation at the classical level. I will also introduce a generalisation of this geometrical framework to 4D field theories, and discuss some of the interesting differences with the 2D case. ---- Part of London Integrability Journal Club. If you are a new participant, please register filling the form at integrability-london.weebly.com. The link will be emailed.