High Energy Physics Seminar Series

SPRING 2025 

 

MAY 7

“Puzzles in 3D Off-Shell Geometries via VTQFT”

CYNTHIA YAN – Stanford University

Abstract: 

We point out a difficulty with a naive application of Virasoro TQFT methods to compute path integrals for two types of off-shell 3-dimensional geometries. Maxfield-Turiaci proposed solving the negativity problem of pure 3d gravity by summing over off-shell geometries known as Seifert manifolds. We attempt to compute Seifert manifolds using Virasoro TQFT. Our results don’t match completely with Maxfield-Turiaci. We trace the discrepancies to not including the mapping class group properly. We also compute a 3-boundary torus-wormhole by extrapolating from an on-shell geometry. We encounter challenges similar to those observed in the comparison between the genuine off-shell computation of a torus-wormhole by Cotler-Jensen and the extrapolation from an on-shell configuration. https://arxiv.org/abs/2502.16686

 

APRIL 30

“Loop Soups and Solution of the  O(n) CFTs in 2 Dimensions”

HUBERT SALEUR – USC Physics and Astronomy and Institute of Theoretical Physics, Saclay

Abstract: 

Statistical Mechanics models are more often than not described by “complex” conformal field theories –  theories which are considerably more difficult to study than their well known minimal cousins. Geometrical problems such as percolation and self-avoiding walks, or the plateau transition in the integer quantum Hall effect, provide a good example of this situation. In this talk I will review work of the last many years aimed at solving the  O(n) loop soup model (conformal loop ensemble). I will explain why the  corresponding CFT is  non-unitary, non rational, and non quasi-rational, and discuss in simple terms how it can be solved using techniques ranging from pure algebra to the bootstrap.

 

APRIL 23

“Codimension-1 Defect in Free Scalar Field Theory”

SEOLHWA KIM – UCLA

Abstract: 

We consider a class of the codimension-1 defects in a free real and non-compact scalar theory, which are time translationally invariant and include some conformal and topological defects.  We describe the defect in two different ways—through a matching condition across it and through a localised interaction along its world volume.  The first description is suitable for the computations using the mode expansion of the fields.  The second description is useful for the perturbative computations, such as the Green’s function and defect anomalous dimension.  Using the Green’s function and the variation of the action, we’ll see that the two descriptions are equivalent.  I’ll describe the computation of the torus partition function in the presence of a time-like defect using the first description and that with a spacelike defect.  With an appropriate rescaling using the defect anomalous dimension, we will find the expected agreement.  I will talk about the density of states and comment on Cardy formula.  If time permits, I’ll sketch our computation of some of the following quantities: the SL(2,R) defect fusion algebra, bound states, monotonically decreasing defect g-function and spacelike quenches.

 

TUESDAY, APRIL 15 at 10:00 AM

* SSC 319*

“Exploring CFT Moments”

DAVID POLAND – Yale University

Abstract: 

I’ll discuss the reorganization of conformal field theory data into moment variables, which seems to be a useful language for describing CFT correlators with large scaling dimensions. In particular, one can analytically derive two-sided bounds on CFT moments in the heavy limit and more generally explore numerical bounds on the space of CFT moments.

 

APRIL 9

“Algebraic Probes of Emergent Spacetime”

SAM LEUTHEUSSER – IAS

Abstract: 

An important property for any candidate theory of quantum gravity is the emergence of classical geometry in an appropriate limit. We describe a framework to understand this emergence using von Neumann algebras as probes of local physics. In the context of the AdS/CFT correspondence, we demonstrate that many non-trivial “type III” algebras emerge in the limit where the number of local degrees of freedom of the boundary CFT becomes infinite. We argue that these non-trivial emergent boundary algebras: i) encode physical operations that can be performed in arbitrary local bulk subregions, ii) are responsible for the causal structure of bulk geometry, and iii) can be used to construct operators that correspond to in-falling time-evolution in an asymptotically AdS black hole.

 

APRIL 2

“Exploring G-ality defects in 2d QFT”

ZHENGDI SUN – UCLA

Abstract: 

Given an anomaly-free finite (non-invertible) 0-form symmetry in 2d QFT, one can consider gauging it. The theories invariant under such gauging admit additional non-invertible symmetries known as the G-ality defect. One famous example is the Tambara-Yamagami(TY) fusion categories describing the self-duality under gauging Abelian groups. To fully describe those non-invertible symmetries, one must also specify their categorical structure, which are nothing but the analog of the ’t Hooft anomaly of the finite group symmetry. In this talk, we will give an overview of the classification of categorical structures for G-ality defects; then we will provide a few concrete examples displaying novel features compared with the well-known TY categories, and demonstrate how the categorical structure can affect the implications of the symmetry.

 

MARCH 26

“Beyond the Supergraviton Elliptic Genus”

MARCEL HUGHES – Nagoya University

Abstract: 

The elliptic genus is an index for 1/4–BPS states in the 2d N=(4,4) symmetric orbifold theories Sym^N(M_4), where M_4 can be K3 or T4; theories that are relevant to type IIB string theory on AdS3 x S3 x M_4. A classic result is the matching of this elliptic genus with the index of the KK spectrum of supergravity on AdS3 x S3 for low enough conformal dimensions. We discuss a generalisation of this supergraviton elliptic genus which also includes boundary modes, as well as its relevance for defining a fortuitous index in these theories.

 

MARCH 19

Spring Break

 

FEBRUARY 26

“The Gravitational Index of 5d Black Holes and Black Strings”

LUCA ILIESIU – UC Berkeley

Abstract: 

In this talk, I will discuss how one can use the gravitational path integral to compute the supersymmetric index of black holes as well as other black objects in string theory. The saddles that I shall describe admit a non-zero temperature, consequently lacking an infinitely long AdS throat that separates the horizon from the asymptotic region, and also admit periodic boundary conditions for fermionic fields around the thermal circle, consequently counting bosonic and fermionic states with an opposite sign. Since the microscopic calculation of these indices is oftentimes well understood yet the saddles that I shall describe now lack the conventional decoupling limit taken in AdS/CFT, our analysis represents a first step towards understanding holography for supersymmetric observables in flat space.

 

FEBRUARY 19

“AdS_3/RMT_2 Beyond the Ramp “

GABRIELE DI UBALDO – UC Berkeley

Abstract: 

In 2307.03707 we introduced a framework for random matrix theory (RMT) in AdS_3 quantum gravity and chaotic 2D CFTs that is manifestly conformal and modular invariant. On the CFT side this leads to a 2d CFT trace formula, analogous to the Gutzwiller trace formula for chaotic quantum systems, which we use to derive necessary and sufficient conditions for an individual 2d CFT to have RMT statistics. Applied to pure 3D gravity, we obtained a microscopic CFT understanding of the off-shell Cotler-Jensen torus wormhole. This wormhole is shown to be exactly dual to RMT_2: the minimal modular invariant completion of the RMT two-point correlator. In work to appear soon, we construct and establish RMT_2 as a modular invariant RMT ensemble which minimally uplifts to 3D the near-extremal dynamics of 2D theories like JT gravity. We construct a modular invariant spectral form factor describing the full ramp-plateau transition. Seen as a candidate SFF of pure 3D gravity, it describes the chaos and discreteness of black hole microstates. We give predictions for n-boundary wormholes in pure 3D gravity and in the n=3 case we exhibit matching with a gravitational ansatz.

 

FEBRUARY 12

“String Perturbation Theory of Klebanov-Strassler Throat “

MANKI KIM – Stanford University

Abstract: 

In this talk, I will explain how to study string perturbation theory of the Klebanov-Strassler solution in the large radius approximation based on open-closed superstring field theory. Combining the large radius expansion and a double scaling limit, we find a perturbative background solution of open-closed superstring field theory that corresponds to the Klebanov-Strassler solution. To illustrate the utilities of this approach, we break supersymmetry of the background by placing a stack of anti-D3-branes at the tip of the throat. We then find a perturbative open string background solution to the third order in the large radius approximation, which agrees with the well-known supergravity analysis of Kachru-Pearson-Verlinde (KPV) on the stability of the anti- D3-brane supersymmetry breaking. The perturbative background solution to the open string field theory we found is expected to be dual to an NS5-brane probing the KS solution.

 

FEBRUARY 5

“Localized Black Holes in AdS3: Thermodynamics and Entanglement Entropy”

ZIXIA WEI – Harvard University

Abstract: 

A holographic conformal field theory (CFT) is a CFT whose low-energy behavior can be described by Einstein gravity in anti-de Sitter spacetime (AdS) with one higher dimension. For a 2D holographic CFT, modular invariance largely determines the spectrum at both low and high energies, leaving only a medium-energy range undetermined. In the corresponding 3D AdS, this implies that the low-energy statistics are described by global AdS plus matter, while the high-energy statistics are governed by the BTZ black hole, independent of the details of the underlying 2D CFT. The specific details of the spectrum are reflected only in the configurations within the medium-energy range, which are not well understood on the AdS3 side. In this talk, we present a class of non-supersymmetric localized black holes in Type IIB supergravity in AdS3 × S3 × T4, which is dual to a 2D CFT (the D1-D5 CFT) in the strong coupling limit. We first study the thermodynamics of these localized black holes and observe that they can dominate over the BTZ black hole and thermal AdS in the medium-energy range left undetermined by the modular bootstrap. This suggests that these solutions provide a pathway to analytically study this “enigmatic” energy window. We then estimate the holographic entanglement entropy associated with these solutions and, surprisingly, find that it is almost identical to that in the BTZ solutions at the same energy. This suggests that certain geometric details are obscured within the “entanglement shadow.” Finally, we will discuss their implications on the CFT side.

 

JANUARY 29

“Chiral Boson at the Edge of Lattice Chern-Simons Theory”

THEO JACOBSON – UCLA

Abstract: 

Regulating chiral quantum field theories on the lattice has been an outstanding problem since the inception of lattice gauge theory. In this talk, I describe a Hamiltonian lattice realization of the 1+1d chiral boson, which is one of the simplest examples of a chiral theory. This theory (both in the continuum and on the lattice) does not exist in isolation, but only as the boundary of a non-trivial topologically ordered 2+1d phase. We describe how to realize (Maxwell) Chern-Simons theory as a Hamiltonian lattice gauge theory, and show that it hosts a chiral edge mode on spatial lattices with boundary.

 

JANUARY 22 

“3D Modularity Revisited”

DAVIDE PASSARO – Caltech

Abstract: 

In this introductory, self-contained talk, I will present some recent developments concerning the modular properties of Ẑ invariants—quantum invariants of three-manifolds originally defined as half-indices of strongly coupled N=2 theories in three dimensions on a solid torus. After motivating the research, and a brief overview of their construction, I will focus on the intricate modular relations that emerge, with a focus on quantum modularity, mock modularity, and Weil representations. The discussion is based on results from arXiv:2403.14920 and aims to be accessible to a broad mathematical and physical audience.

 

______________________

FALL 2024

 

NOVEMBER 27 – 

THANKSGIVING HOLIDAY

 

*TUESDAY, NOVEMBER 19 – 

“Derivation of TQFT Gravity/Ensemble Holography”

TOLYA DYMARSKY– University of Kentucky

Abstract:

We outline a general derivation of holographic duality between “TQFT gravity” – the path integral of a 3d TQFT summed over different topologies – and an ensemble of boundary 2d CFTs. The key idea is to place the boundary ensemble on a Riemann surface of very high genus, where the duality trivializes. The duality relation at finite genus is then obtained by genus reduction. Our derivation is generic and does not rely on an explicit form of the bulk or boundary partition functions. It guarantees unitarity and suggests that the bulk sum should include all possible topologies. In the case of Abelian Chern-Simons theory with compact gauge group we show that the weights of the boundary ensemble are equal, while the bulk sum reduces to a finite sum over equivalence classes of topologies, represented by handlebodies with possible line defects.

 

NOVEMBER 13 – via ZOOM

“Conformally Invariant Chern-Simons Actions in 3+1 Dimensions: Holographic Shadows of 2T-Physics”

SOPHIA SINGH– Brown University

Abstract:

TBA

 

*TUESDAY, NOVEMBER 12 – 

“Classical Double Copy: Solutions, Horizons, and Penrose Limits”

CYNTHIA KEELER– Arizona State University

Abstract:

We will review the classical double copy, which maps exact solutions of classical gauge theories like electromagnetism, to solutions of general relativity. We will cover both the Kerr-Schild and Weyl formulations of this map.  Following a survey of known exact solutions, we will review why a position-space classical solution double copy is even feasible.  We will briefly discuss some perturbative approaches, and then close by relating several gravitational objects (including horizons and Penrose limits) to their gauge theory analogues.

 

NOVEMBER 6 – 

“Black Holes from Weak Jacobi Forms”

SUZANNE BINTANJA– UCLA

Abstract:

In this talk I will revisit the connection between modular forms and black hole entropy. I will introduce the notion of a weak Jacobi form (wJf), and use modular crossing kernels to extract asymptotic expansions of the Fourier coefficients of wJfs. When combined with conditions inspired by AdS/CFT we find a broad range of parameters in which the leading order behaviour is universal and Cardy-like, while the first sub-leading logarithmic correction depends on the “light” data of the wJf. When there is a dual gravity description we can match the asymptotic expansion to the black hole entropy. By doing so we find a precise microscopic interpretation to the logarithmic corrections to the entropy of BPS black holes in N=2,4 ungauged supergravity in four and five dimensions.

 

OCTOBER 30 – 

“A Bootstrap Principle for the Uniqueness of String Amplitudes”

AARON HILLMAN– Caltech

Abstract:

Ordinary consistency conditions on 2->2 scattering will not yield string amplitudes as the unique answer. This has motivated new work on the constraints from consistent multi-particle scattering. Still in the 2->2 world, one can ask whether there exists a principle which might uniquely constrain the spectrum and scattering of strings. We identify a principle dubbed level truncation which, when paired with the usual constraints, defines an infinite set of polynomial equations in terms of a set of free set of dual-resonant Ansatz parameters. The spectrum is unconstrained in the Ansatz and its unique solution is the Coon spectrum. When imposing superpolynomial boundedness and strict dual resonance, only Veneziano remains as a solution.  We present the generalization of this bootstrap to a closed-string type Ansatz, and the one-parameter deformation of the Virasoro-Shapiro amplitude that it admits. We discuss possible avenues for future work.

 

OCTOBER 23 – 

“Quantum Information Scrambling of Algebras and Quantum Mereology”

PAOLO ZANARDI– USC

Abstract:

I will give an informal and gentle whiteboard introduction to our work on quantum scrambling  of observable algebras and (perhaps, time permitting) to its application to quantum mereology. Here below a few references:

https://quantum-journal.org/papers/q-2022-03-11-666/

https://quantum-journal.org/papers/q-2024-07-11-1406/

https://journals.aps.org/pra/abstract/10.1103/PhysRevA.107.042217

 

OCTOBER 16 – 

“Bootstrapping BFSS at infinite N”

HENRY LIN – Stanford University

Abstract:

I will discuss analytical and numerical bootstrap bounds on simple correlators in the BFSS model/D0-brane quantum mechanics. I will present strong evidence that the bootstrap method is dramatically more efficient than Monte Carlo at large N and low temperatures. This talk is based on http://arxiv.org/abs/2302.04416 and work in progress with Zechuan Zheng.

 

*TUESDAY, OCTOBER 8 – 3:00 PM*

“Strings Near the Conformal Boundary of AdS3”

VIT SRIPRACHYAKUL – ETH Zurich

Abstract:

I will discuss recent development in AdS3/CFT2 duality with pure, non-minimal NSNS flux. This comes from adopting a certain approximation. I will describe how such an approximation allows us to calculate generic n-point ground state amplitudes in bosonic string theory. This then enables us to deduce the bosonic dual CFT. I will also discuss what happens when we add supersymmetry and when we consider excited states.

 

OCTOBER 2 – NO SEMINAR

 

SEPTEMBER 25 – 

“Quantum Scrambling, Operator Entanglement and Operator Algebras”

Faidon Andreadakis – USC

Abstract:

Complex quantum dynamics lead to the generation of non-local correlations that delocalize information initially stored in local degrees of freedom, a phenomenon referred to as scrambling. In this talk, I will motivate and describe the concept of quantum information scrambling, demonstrating the role of non-commutativity and entanglement. Some connections with quantum thermalization and information propagation in local quantum many-body systems will be briefly mentioned. Then, I will show how the on-average scrambling caused by a unitary evolution is directly related to information-theoretic properties of the dynamics, like operator entanglement and entropy production. Finally, a more general algebraic framework of scrambling will be discussed, which incorporates a wider range of properties of quantum evolutions, like coherence generation, depending on the algebra of observables of interest.

 

SEPTEMBER 18 – 

“Universality of 2D CFT Phase Diagram at Large Central Charge”

SRIDIP PAL – Caltech

Abstract:

In a modular invariant 2D CFT with a fixed central charge, the Cardy formula gives a universal density of states at asymptotically high energy (E \rightarrow\infty). Hartman, Keller, and Stoica (HKS) extended the regime of validity of this formula for states with E \propto c with c \rightarrow \infty, assuming a sparseness condition on the spectrum below E < 0. In the canonical ensemble, this is equivalent to the familiar statement, as expected from holography, that for \beta < 2\pi, the BTZ black hole dominates, and for \beta > 2\pi, thermal AdS dominates. Upon turning on the temperature for both the left and right movers, assuming the spectrum is sparse below twist ( = 2 min(h,\bar{h})) c/12, HKS conjectured and produced numerical evidence that the free energy is universal except for the hyperbola \beta_L \beta_R = 4\pi^2; i.e., for \beta_L \beta_R > 4\pi^2, thermal AdS dominates and for \beta_L \beta_R< 4\pi^2, the black hole dominates. We analyze the modular bootstrap equation at large central charge and prove this conjecture. Our formalism allows us to explore the consequence of sparseness by taking the spectrum to be sparse below twist \alpha (c-1)/12, where \alpha is a tunable parameter in (0,1]. The \alpha = 1 is the case related to the HKS conjecture. We show that for \alpha \rightarrow 0,, the region where the free energy is universal reduces in a quantifiable manner.

 

SEPTEMBER 11 – 

“Classification of Generalized Gaugings in 2d QFT”

CONGHUAN LUO – USC

Abstract:

Gaugings are powerful tools for creating new theories, studying general properties of symmetry and relating known theories that have very different appearances. Crucially, the notion of discrete gauging generalizes to various versions of generalized symmetries, especially non-invertible symmetry which I will briefly review. After that, I will introduce a way of systematically bootstrapping all the possible discrete generalized gaugings of a 2d QFT equipped with (non-invertible) global symmetry, which makes use of the relation between discrete gaugings and topological interfaces. As an example, I will briefly illustrate a specific symmetry in 2d c=1 CFT on the orbifold branch.

 

SPRING 2024

APRIL 24 – 

“Topological Interfaces and Gauging Generalized Symmetries”

YIFAN WANG – New York University

Abstract:

We’ll describe gauging generalized symmetries in two-dimensional quantum field theory in terms of topological interfaces. We will see that familiar properties one encounters in gauging conventional invertible symmetries generalize naturally to non-invertible symmetries in this physical perspective. We will discuss a bootstrap approach to classify such topological interfaces, and correspondingly the different ways of gauging. We illustrate this general procedure for concrete generalized symmetries realized by concrete 2d CFTs and explain the physical consequences.

 

APRIL 17

“Open-Closed String Duality and Topological Recursion”

ASHTON LOWENSTEIN – USC, Physics and Astronomy

Abstract:

A single family of differential equations, called string equations, has the ability to describe two classes of matrix models dual to non-supersymmetric and supersymmetric two-dimensional string theories. The string equations naturally contain information about both the open and closed string sectors of the theories, making them a useful tool to study open-closed duality. The perturbative solutions to these differential equations can be used to calculate all observables in the models, including asymptotic boundary partition functions and FZZT brane quantities. I will provide several examples of the utility of open-closed duality, including calculating the trumpet path integral and Weil-Petersson volumes in arbitrary topological gravity backgrounds, with and without supersymmetry.

 

APRIL 10

“Non-Perturbative Effects in 2D Conformal Field Theories via Resurgence”

VIRAJ MERULIYA – McGill University

Abstract:

In this talk, I will consider two-dimensional Conformal Field Theories (CFTs) in the semi-classical limit of large central charge-c. Observables within this regime are amenable to analysis via a 1/c expansion, revealing an asymptotic series that demands the inclusion of non-perturbative effects. Using techniques like Borel resummation, we can systematically study these effects. These ideas will be concretely applied to study the structure constants in Liouville theory using the DOZZ formula. We demonstrate how non-perturbative effects in this context correspond to complex solutions to the Liouville equation. Along the way, we show that the Borel transform has a much simpler expression than the original DOZZ formula. This can provide a better understanding of its analytic structure and applications.

 

APRIL 3

“A Synergy of Shockwaves, Edge Modes, and Infrared Physics”

TEMPLE HE – Caltech

Abstract:

In this talk, I will focus on two interesting directions of research in the infrared sector of gauge theories and gravity. First, we study the relationship between shockwave geometries and the gravitational memory effect in four-dimensional asymptotically flat spacetime. In particular, we show the ‘t Hooft commutation relations of shockwave operators are equivalent to the commutation relation between soft and Goldstone modes parametrizing a sector of the gravitational phase space. Second, we present a concrete connection between soft modes on the celestial sphere and entanglement edge modes in abelian gauge theory, paving the way to study entanglement properties of soft modes.

 

MARCH 27

“Unoriented Perturbative JT Gravity and Matrix Models”

WASIF AHMED – USC

Abstract:

We will explore the perturbative expansion of Jackiw-Teitelboim (JT) gravity on oriented surfaces in terms of multicritical matrix models. Expanding our horizons, we will see that to incorporate unoriented surfaces in the perturbative expansion, we need the double scaling limit of the multicritical matrix models in the $$\beta=1$$ Dyson-Wigner class. They capture the physics of 2D quantum gravity coupled to minimal matter on unorientable surfaces, otherwise called unoriented minimal strings. Through a similar framework as oriented JT gravity, we will derive a formula for the density of states valid to all orders in perturbation theory, show how to define an interpolation between the multicritical models and that a certain interpolation among an infinite number of them provides an alternative definition of unoriented JT gravity.

 

MARCH 20

“Bootstrap Meets Experimental Data”

NING SU – Caltech

Abstract: 

The bootstrap method explores fundamental consistency conditions to constrain physical observations. The consistency conditions often translate into highly non-trivial numerical problems. In this talk, I will show that, with advanced numerical techniques, formal constraints such as unitarity and crossing symmetries lead to precise predictions for experimental phenomena in condensed matter and particle physics. I will discuss two experiments: the He4 superfluid phase transition and pion scattering. In both cases, bootstrap results provide insights into the experimental analysis. 

 

FEBRUARY 28

“Holography and Regge Phases at Large U(1) Charge”

GIULIA FARDELLI – Boston University

Abstract:

 A single Conformal Field Theory (CFT) can have a rich phase diagram with qualitatively different emergent behaviors in a range of different regimes parameterized by the conserved charges of the theory. In this talk, I will consider a CFT with a global U(1) current and explore the phase diagram as a function of the U(1) charge Q and angular momentum J, particularly at large J and Q. By taking the large J limit first, we are able to employ a dual holographic interpretation in AdS_{d+1} to predict the energy spectrum of Q-particle states. This limit has been studied in detail for Q=2, yielding very general results applicable to unitary CFTs in d>2. When Q is also taken to be large, the description is more complicated; nevertheless, we can draw interesting conclusions about the energy spectrum under certain assumptions. I will conclude with a concrete example, the O(2) model in 3d, highlighting interesting connections with recent (and less recent) results in this context.

 

FEBRUARY 21

“Tauberian Theorems and High Energy Asymptotic Data in CFT”

SRIDIP PAL – Caltech

Abstract:

In this talk, I will introduce Tauberian techniques, a widely used tool in analytical number theory, to expound on the universality in the \textit{averaged} asymptotic data of 2D CFT, specifically to probe the granularity of the averaging process and learn about the asymptotic spacing of Virasoro primaries. In particular, we show that for a unitary modular invariant 2D CFT with fixed central charge $c>1$, having a nonzero twist gap in the spectrum of Virasoro primaries, for sufficiently large spin $J$, there always exist spin $J$ operators with twist falling in a vanishingly small interval $\left(\frac{c-1}{12} – \varepsilon , \frac{c-1}{12} + \varepsilon \right)$ with $\varepsilon=O(J^{-1/2}\log J)$ i.e the twist spectra is dense. We establish that the number of Virasoro primary operators in such a window has a Cardy-like i.e., $\exp\left[2\pi \sqrt{\frac{(c-1) J}{6}}\right]$ growth. A similar result is then proven for a family of holographic CFTs with the twist gap growing linearly in c and a uniform boundedness condition, in the regime $J>\!\!\!>c^3>\!\!\!>1$. Our result sheds light on the validity regime of Schwarzian approximation in describing the near-extremal rotating BTZ black holes (without electric charge). We make further conjectures on potential extension of the above results to CFTs with conserved currents.

 

FEBRUARY 14

“Universal Properties in ICFTs”

YUYA KUSUKI – Caltech

Abstract:

Conformal interfaces are not well-studied except for special interfaces called topological interfaces. This lack of study is due to general interfaces breaking symmetry, where some powerful tools in CFT are not applicable. On this background, AdS/CFT can be a powerful tool. In this talk, we make use of AdS/CFT to understand universal properties of conformal interfaces in 2D. Interestingly, we show that the generalized holographic c-theorem can be interpreted as the upper bound on the entanglement between two (possibly different) systems. Moreover, we also show its CFT proof by using the results on the gravity side as a hint. Finally, we give the higher-dimensional generalization of our results. The key is that methods on the gravity side generally do not depend on dimensions, unlike QFT methods. This is another advantage of AdS/CFT to explore quantum many-body systems.

 

FEBRUARY 7 

“AdS Bulk Locality from Dispersive CFT Functionals”

CYUAN-HAN CHANG – Caltech

Abstract:

It is a long-standing conjecture that any CFT with large N and a large gap in the higher-spin single trace spectrum should have a gravity dual in the AdS whose low energy effective field theory is local at the length scale much smaller than the AdS radius (suppressed by the large gap of the CFT). I will discuss how to establish a sharp form of this conjecture using analytic conformal bootstrap. The main tool is a special class of CFT functionals called dispersive functionals. I will explain how to systematically construct them using commutativity of null-integrated operators in CFT. If time permits, I will show that the action of dispersive functionals on conformal blocks with heavy dimensions, which is an important quantity in the bootstrap method, is dominated by a saddle configuration and can be precisely related to dispersion relations of scattering amplitudes in flat spacT Functionals”e.