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String Theory Journal Club

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Zapraszamy do sali 5.42, ul. Pasteura 5 o godzinie 12:15

Jackson Fliss (University of Cambridge)

Keeping matter in the loop in 3d quantum gravity

Chern-Simons theory provides an attractive framework for quantizing 3d gravity without reference to holography. But how do we describe matter in CS gravity while retaining its useful features? In this talk, I will introduce a "Wilson spool," which provides an effective description of massive one-loop determinants directly as a gauge-invariant object. The spool can be heuristically viewed as a collection of Wilson loops winding in the Euclidean spacetime. I will illustrate its utility for reproducing one-loop determinants of massive scalar fields in both Anti-de Sitter and de Sitter backgrounds. In the context of de Sitter quantum gravity, exact results in Chern-Simons theory allow one to calculate the spool in the quantum gravity path-integral with finite G_N. This provides a method for investigating how dynamical gravity renormalizes the physics of massive matter. Zoom link: https://uw-edu-pl.zoom.us/j/98210507354

Zapraszamy do sali 5.42, ul. Pasteura 5 o godzinie 12:15

Stephan Stieberger (MPI Munich)

Scattering Amplitudes on Riemann Surfaces

Riemann surfaces are ubiquitous for a geometrical description of scattering amplitudes of particles. In particular their symmetries become simple manifestations of properties of complex analysis. As an example we will discuss relations between gauge and gravitational amplitudes by analyzing world-sheet properties of closed and open strings. Link: https://uw-edu-pl.zoom.us/j/92154293299

Zapraszamy do sali 5.42, ul. Pasteura 5 o godzinie 12:15

Jan Boruch (IFT UW)

Chords and the ground state sector of N=2 SYK

I will talk about the ground state sector of the supersymmetric N=2 SYK model in the double scaling limit. In this limit the model is exactly solvable using chord diagrams, which can be given a natural interpretation in terms of the bulk gravity dual. I will review the chord diagram technique and explain how it allows us to study the boundary SYK model from the bulk perspective.

Zapraszamy do sali 5.42, ul. Pasteura 5 o godzinie 12:15

Dmitry Noshchenko (University of Amsterdam)

Bailey pairs, Rogers-Ramanujan identities and conformal field theory

We will discuss the role of q-identities of Rogers-Ramanujan type played in conformal field theories. Another useful concept is Bailey pairs, which produce an infinite towers of such identities and are conjecturally related to RG flows for various rational CFTs. We note that the subject gained the most attention in the 80's and 90's, but since then has not been developing much. It is therefore interesting to argue about the prospectives and possible generalizations of this approach. Online link: meet.google.com/gbj-tmns-err

Zapraszamy do sali 5.42, ul. Pasteura 5 o godzinie 10:15

Michał Heller (Ghent University)

Resurgence in relativistic hydrodynamics 10 years after the first encounter

It is by now rather well studied that perturbative expansions in interacting quantum systems know about non-perturbative effects via their large order behavior. I will discuss progress in the last decade in understanding the origins of hydrodynamic behavior in quantum field theories (and their effective descriptions) that originates from adopting resurgence in this novel to it setting.

Zapraszamy do sali 5.42, ul. Pasteura 5 o godzinie 12:15

Abhigyan Saha (IFT UW)

Defining extended TFTs and a classification result

We will first try to motivate a category theoretic definition of an extended TFT from scratch and without pre requisites. The goal is to discuss a result classifying extended TFTs in the bicategorical case as a Frobenius algebra. The talk will be very light with mostly definitions, diagrams and examples; and without any involved computations. Online link: meet.google.com/gbj-tmns-err

Zapraszamy do sali 4.50, ul. Pasteura 5 o godzinie 10:15

Joao Caetano (CERN)

Large Charge 't Hooft Limit of N = 4 Super Yang-Mills

N=4 super-Yang-Mills (SYM) in four dimensions is integrable in the planar limit, allowing exact computations for a variety of observables. I will demonstrate that the large charge sector of N = 4 SYM with the SU(2) gauge group provides another interesting solvable corner, which is far from the planar limit but nevertheless exhibits similar structures. We study non-BPS operators obtained by small deformations of half-BPS operators with R-charge J in the double-scaling limit with J → ∞ and λ_J ≡ g^2 J/2 fixed. I will show thatthe spectrum and correlation functions in this large charge 't Hooft limit are constrained by the centrally-extended SU(2|2)^2 symmetry that played a crucial role in integrability in the planar limit. I will also show exact results in the large charge 't Hooft limit for certain three and four point functions. In the case of four point functions, I will be able to study integrated correlators for arbitrary SU(N) gauge groups by recasting results from supersymmetric localization to an 'emergent' matrix model of size J/2, and matchingit against the large charge analysis.

Zapraszamy do sali 5.42, ul. Pasteura 5 o godzinie 12:15

Dimitrios Patramanis (IFT UW)

The Krylov Panopticon

In recent years the notion of computational complexity has become the object of intensive study for physicists despite the fact that it is a concept originating from computer science. So why is the physics community so interested in this particular topic and what can we hope to learn from it? In my talk I will briefly address these questions in a general context and then proceed to discuss the measure called Krylov complexity in particular. This measure, although one of many, has become very popular because of its wide range of applicability and computability. I will elaborate on these qualities by reviewing its construction and highlighting certain aspects that in principle make it an interesting probe for any quantum system. Hence, it can be likened to a panopticon from which one can gain access to information about systems ranging from condensed matter to exotic QFTs and possibly holography. Finally, I will present some of the latest advancements and discuss how they shape our current understanding of Krylov complexity and its place in the “zoo” of complexity measures. Online link: meet.google.com/gbj-tmns-err

Zapraszamy do sali 4.50, ul. Pasteura 5 o godzinie 10:15

Watse Sybesma (University of Iceland)

An outsider's perspective on information recovery in de Sitter space

Entanglement islands play a crucial role in our understanding of how Hawking radiation encodes information in a black hole, but their relevance in cosmological spacetimes is less clear. In this talk, I review some aspects of entanglement islands in black holes, and present a protocol for information recovery in de Sitter space in two dimensions. This setup revolves around a two-dimensional model of gravity containing a domain wall that interpolates between de Sitter space and Rindler space. This talk is mainly based on the results of https://arxiv.org/abs/2210.12176. Online link: meet.google.com/gbj-tmns-err

Zapraszamy do sali 5.42, ul. Pasteura 5 o godzinie 12:15

Leszek Hadasz (Uniwersytet Jagielloński)

Making sense of the Root-$T\bar{T}$ deformation

Just over a year ago, several authors (Christian Ferko, Alessandro Sfondrini, Liam Smith, and Gabriele Tartaglino-Mazzucchelli) initiated studies of the consequences of introducing into two-dimensional field theories a one-parameter family of deformations, which they called the Root-$T\bar{T}$ deformation. Their work, as well as the subsequent papers extending their results, focus on classical theory. In my talk, I will present an idea how to analyze the consequences of Root-$T\bar{T}$ deformations for a quantum, two-dimensional conformal field theory.

Zapraszamy do sali 4.50, ul. Pasteura 5 o godzinie 10:15

Alexander Frenkel (Stanford University)

Entanglement Edge Modes in Noncommutative Matrix Backgrounds

I will talk about an upcoming paper on the general structure of entanglement edge modes in emergent noncommutative matrix backgrounds. In particular, I will show that for arbitrary subregions in arbitrary backgrounds the edge mode representation structure precisely contains the information about topology and geometry of the entanglement cut, and this area-law like structure holds to all energies despite nonlocal interactions and UV/IR mixing. There is also an intimate connection to how we think about entanglement in gauge theory tensor networks I can discuss.

Zapraszamy do sali 4.50, ul. Pasteura 5 o godzinie 14:00

Gerben Oling (Nordita)

Carroll limits, celestial CFTs and flat space holography

I will discuss recent advances in Carroll limits of field theories and their relation to celestial holography. Motivated by asymptotic symmetries and their relation to soft photons, celestial holography maps four-dimensional scattering amplitudes to correlators in a two-dimensional CFT. However, such celestial CFTs have several nonstandard features, and only few explicit examples are known. On the other hand, one can consider flat space limits of AdS/CFT which naturally lead to three-dimensional CFTs with Carroll symmetry. After reviewing some of the recent progress on applications of non-Lorentzian geometry in limits and expansions of Lorentzian theories such as general relativity and string theory, I will introduce a related geometric method for constructing Carroll CFTs from a limit of Lorentzian CFTs, and I will discuss their relation to celestial CFTs. Zoom link: https://uw-edu-pl.zoom.us/j/94454442398

Zapraszamy do sali 5.42, ul. Pasteura 5 o godzinie 12:15

Nikolai Iorgov (Bogolyubov Institute for Theoretical Physics, Kyiv, Ukraine)

Isomonodromic deformations and conformal field theory

This talk overviews recent results relating isomonodromic tau functions (including Painleve tau functions) and conformal blocks of 2D CFT with central charge c=1. Several directions generalizing this relation will be discussed. Link: meet.google.com/gbj-tmns-err

Zapraszamy do sali 5.42, ul. Pasteura 5 o godzinie 12:15

Miłosz Panfil (IFT UW)

Correlation functions in Integrable Quantum Field Theories at finite temperatures

I will provide an overview of our work on the Thermodynamic Bootstrap Program (TBP), which is a new tool for calculating form-factors between states that have a finite density of particles. TBP extends the vacuum bootstrap program and enables the computation of dynamic correlation functions at finite temperature. I will show our findings on the low-energy behaviour of two-point functions of local density operators. Online link: meet.google.com/gbj-tmns-err

Zapraszamy do sali 5.42, ul. Pasteura 5 o godzinie 12:15

Balázs Pozsgay (Eötvös Loránd University Budapest)

Exotic symmetries and breakdown of ergodicity from hard rod deformations

We treat a new mechanism for ergodicity breaking in one dimensional quantum many body systems. We treat spin chains with local Hamiltonians, which have a special fine tuned form: there is interaction in the system, nevertheless the models have a large non-commutative symmetry algebra, generated by Matrix Product Operators (MPO). Meanwhile, the models are NOT integrable, and not exactly solvable. The exotic symmetries cause exact degeneracies in the finite volume spectrum, leading to a breakdown of thermalization. The mechanism we treat is a special type of "Hilbert space fragmentation''. It appears that our models are the first ones, where non-commutative MPO symmetries are found, such that the models are not integrable. Transmisja online: https://uw-edu-pl.zoom.us/j/94797623941, meeting ID: 947 9762 3941.

Zapraszamy do sali 5.42, ul. Pasteura 5 o godzinie 10:15

Shaun Hampton (IPhT, Saclay)

Bootstrapping the effect of the twist operator in symmetric orbifold CFTs

In this talk I will discuss recent work on computing effects of the twist operator in symmetric orbifold CFTs. Traditionally, these effects can be understood by using the covering space method where one must use covering maps. More recently, we have developed a method which uses a Bogoliubov ansatz and conformal symmetry to bootstrap these effects. I will present results for the single twist case and discuss extensions to the multi-twist scenario. Zoom link: https://uw-edu-pl.zoom.us/j/92918049449, meeting ID: 929 1804 9449

Zapraszamy do sali 5.42, ul. Pasteura 5 o godzinie 12:15

Diego Liška (University of Amsterdam)

A principle of maximum ignorance for semiclassical gravity

Recent findings involving Euclidean and replica wormholes have shown that the path integral of semiclassical gravity in AdS provides a "coarse-grained" description of its holographic CFT. In this seminar, I will discuss a statistical interpretation of these results, exploring various notions of coarse-graining and state-averaging within a unified framework. I will establish a probability distribution on the space of density matrices that is maximally ignorant about the UV but can still reproduce low-energy observables. This approach is similar to the eigenstate thermalization hypothesis and can be described with a simple state-averaging ansatz. Finally, I will demonstrate how this ansatz reproduces several wormhole amplitudes in three and higher dimensions. The ideas presented in this seminar are based on upcoming work with Jan de Boer, Boris Post, and Martin Sasieta.

Zapraszamy do sali 4.50, ul. Pasteura 5 o godzinie 10:00

Felix Haehl (University of Southampton)

Effective theory of sub-maximal chaos

I will present progress on formulating an effective description of the quantum butterfly effect at late times. After discussing maximally chaotic examples, I will turn to a particular limit of the SYK model that displays sub-maximal chaos and discuss its effective description. The final results can be matched in detail to stringy corrections to the gravitational eikonal S-matrix in holographic CFTs, including a stringy Regge trajectory, bulk to boundary propagators, and multi-string effects that are unexplored holographically.

Zapraszamy do sali 5.42, ul. Pasteura 5 o godzinie 12:15

Diptarka Das (IIT Kanpur)

Virasoro blocks and quasimodular forms

We analyse Virasoro blocks as an expansion in heavy exchange dimension. For the one point torus block and the four point sphere block each order in the expansion can be written as polynomials in the Eisenstein series. These polynomials are further constrained to satisfy a recursion relation, which can be re-expressed as a noiseless KPZ equation for the blocks. This structure can be utilized along with the Zamolodchikov recursions to develop an algorithm to construct blocks in the heavy regime. We apply our results to find the corrections to averaged heavy-heavy-light OPE coefficients.

Zapraszamy do sali 5.42, ul. Pasteura 5 o godzinie 12:15

Helder Larraguivel (IFT UW)

A-polynomials, symmetries and permutohedra for quivers and knots

Supersymmetric theories and topological field theories are examples of exactly solvable quantum field theories. Although for very different reasons, it is possible to compute observables non-perturbatively. Surprisingly, string theory predicts that a certain class of supersymmetric theories characterised by a directed graph, called a quiver, are dual to certain topological field theories, which encode knot invariants. This duality is now known as the knots-quivers correspondence. We will explore this duality in two ways: First, we show that several quivers may be associated to the same knot. We find simple symmetry transformations relating all the quivers associated to the same knot. We further discover that this rich web of dualities is constructed from simple combinatorial objects known as permutohedra. Second, A-polynomials encode the leading classical behaviour of knot invariants. We then extend the notion of A-polynomials to quivers, and provide explicit formulas for various examples.

Zapraszamy do sali 5.42, ul. Pasteura 5 o godzinie 12:15

Marko Stosic (Instituto Superior Técnico, Lizbona)

HOMFLY-PT polynomials, homologies, and differentials

In this talk I will present some of the main ideas behind the quantum invariants of knots: mainly Jones and HOMFLY-PT polynomials, and their categorifications/refinements in the form of Khovanov and HOMFLY-PT homologies, with the emphasis on the rich structure of differentials on these homologies. The existence of such differentials were originally conjectured by Dunfield, Gukov and Rasmussen in 2005, by using physics insights, and since then many of these things have been proved, expanded and generalized. The goal of the talk is to present some basic ideas of this theory, with various examples (and pictures), possibly together with the overview of the some of the more recent results.

Zapraszamy do sali 5.42, ul. Pasteura 5 o godzinie 12:15

Maciej Kolanowski (IFT UW)

Extremal black holes – a few (classical) surprises

We investigate the geometry near the horizon of a generic, four-dimensional extremal black hole. When the cosmological constant is negative, we show that (in almost all cases) tidal forces diverge as one crosses the horizon, and this singularity is stronger for larger black holes. Moreover, nearly-extremal black holes have large tidal forces at the horizon. Holographically, this singularity is reflected in an anomalous scaling of the specific heat with temperature. The situation becomes even more drastic in five dimensions where (due to the same mechanism) the extremal RN AdS becomes an RG-unstable fixed point. We discover a plethora of new fixed points described by black holes' horizons – all of them are not stable. Based on 2210.02473 and 2211.01385. Joint work with Gary Horowitz and Jorge Santos.

Zapraszamy do sali 5.42, ul. Pasteura 5 o godzinie 12:15

Rui Wang (China University of Mining and Technology, Beijing)

Superintegrability for partition function hierarchies with W-representations

In this talk, I'll introduce our recent works on the construction of the (β-deformed) partition function hierarchies with W-representations. Based on the W-representations, we analyze the superintegrability property and present their character expansions with respect to the Schur polynomials and Jack polynomials, respectively. In addition, the construction of the super partition function hierarchies with W-representations and their character expansions with respect to the Jack superpolynomials will be introduced.

Zapraszamy do sali 5.42, ul. Pasteura 5 o godzinie 12:15

Ramadevi (Indian Institute of Technology Bombay)

Chern-Simons field theory invariants, double twist knots and quivers

I will briefly review knot invariants from Chern-Simons theory. Recent developments on knot-quiver correspondence motivated us to focus on obtaining quivers associated with a class of knots called double twist knots. I will present our results during this talk.

Zapraszamy do sali 5.42, ul. Pasteura 5 o godzinie 12:15

Dongsheng Ge (IFT UW)

Entanglement and geometry from subalgebras of the Virasoro

In this work we study families of generalised coherent states constructed from SL(2,R) subalgebras of the Virasoro algebra in two-dimensional conformal field theories. We derive the energy density and entanglement entropy and discuss their equivalence with analogous quantities computed in locally excited states. Moreover, we analyze their dual, holographic geometries and reproduce entanglement entropies from the Ryu-Takayanagi prescription. Finally, we outline possible applications of this universal class of states to operator growth and inhomogeneous quenches.

Zapraszamy do sali 5.42, ul. Pasteura 5 o godzinie 12:15

Suchetan Das (IIT Kanpur)

Driven CFTs: OTOC and holography

Studying the notion of scrambling or chaos in non-equilibrium systems is an active area of research which may uncover some interesting physics behind thermalization or ergodicity in an open system as well as dynamics of blackhole creation or evaporation in holography. Floquet CFTs provide us with an analytically tractable class of models for studying certain out of equilibrium properties. The most interesting feature of such floquet CFTs is the emergence of a rich phase structure in the parameter space of the theory – the so-called heating phase, non-heating phase, and a transition between them. I will summarize some of our recent results and new features on computations of Out of Time Ordered Correlators (OTOC) in Conformal Field Theories (CFTs) subjected to either discrete or continuous drive protocols and how they are different from the behavior of OTOCs in thermal equilibrium. I will also discuss some ongoing work on the holographic realizations of different phases in the same setup.

Zapraszamy do sali 5.42, ul. Pasteura 5 o godzinie 12:15

Souradeep Purkayastha (IFT UW)

Matrix Models, Random Partitions and Phase Transitions

Random matrix models have been known for a while to have connections to character theory and random partitions; using these, various phenomena on the matrix model side can be quantitatively studied. In this talk I will present some recent results and upcoming work in this direction. First, we take up the unitary Gross-Witten-Wadia model, and its orthogonal and symplectic generalizations, and describe the large N phase space structure for arbitrary coupling constants using the random partition approach. Second, we discuss how a random partition description can be made for other partition functions, taking the N=1 superconformal index for quiver gauge theories as an example.

Zapraszamy do sali 4.50, ul. Pasteura 5 o godzinie 12:15

Soo-Jong Rey (Korea Academy of Science & Technology, Korea)

Holography of Asymptotically Safe Gauge Theories

Safe theories are quantum field theories whose continuum limit is defined by a non-Gaussian ultraviolet fixed point when the ultraviolet cutoff is removed. In this talk, I put forward "safe" gauge-string correspondence program: d-dimensional safe gauge theories are holographically dual to (d+1)-dimensional noncritical string theories in asymptotically anti-de Sitter space. I present evidence for this correspondence. Safe theories can feature in the infrared both a weak coupling phase and a strong coupling phase on either side of the ultraviolet fixed point. They correspond respectively to dilaton and warp factors taking domain-wall or Liouville-wall profiles on asymptotically anti-de Sitter space. The weak coupling phase provides a solvable holographic renormalization group flow while the strong coupling infrared phase provides a runaway-free alternative to holographic QCD. I finally outline open issues for research program.

Zapraszamy do sali 5.42, ul. Pasteura 5 o godzinie 10:00

Andrew Rolph (University of Amsterdam)

Cost of holographic path integrals

[Note: the seminar will take place in 4.49 lecture room!] How complex is a path integral? In this talk, I will introduce proposals for the gravitational dual of computational cost in holographic field theories. To define terms, in Nielsen's geometric approach, complexity is the length of the shortest path between a reference and target state, while cost is the length of a general, not-necessarily-shortest path. To compare to holographic state complexity proposals, our proposals are different in that: (1) the boundary dual is cost, a quantity that can be optimised to state complexity, (2) our set of proposals is large: all functions on all bulk subregions of any co-dimension which satisfy the physical properties of cost, and (3) the proposals are by construction UV-finite. Lastly, I will explain how the path integrals, which we are proposing the cost of, fit in the framework of holographic $T\bar T$. The talk is based onarXiv:2203.08842.

Zapraszamy do sali 5.42, ul. Pasteura 5 o godzinie 12:15

Mayuko Yamashita (Kyoto University)

Classification of invertible QFTs via algebraic topology

Recently, there has been a growing interest in classification of quantum field theories (QFTs) using algebraic topology. Among all QFTs, invertible ones are the most basic class to study. Their classification is important because they arise in condensed matter physics as well as the study of anomaly. These theories are nicely classified by generalized cohomology theories. In this talk, I will give an overview of this topic and explain my related works on Anderson dual cohomology theories (joint work with Kazuya Yonekura) and an application to anomaly in heterotic string theory (joint work with Yuji Tachikawa).

Zapraszamy do sali 5.42, ul. Pasteura 5 o godzinie 12:15

Joaquin Turiaci (IAS Princeton)

Solvable models of quantum black holes: An overview of Jackiw-Teitelboim gravity

I will review recent developments in Jackiw-Teitelboim (JT) gravity. This is a simple solvable model of quantum gravity in two dimensions (that arises e.g. from the s-wave sector of higher dimensional gravity systems with spherical symmetry). Due to its solvability, it has proven to be a fruitful toy model to analyze important questions such as the relation between black holes and chaos, the role of wormholes in black hole physics and holography, and the way in which information that falls into a black hole can be recovered.