Jonathan Harper (YITP)
Time: 10:00 - 11:00
Title: Multi-trace measure in AdS3/CFT2
Abstract: TBA
Slide: The multi-trace generalizes the trace of many copies of the reduced density matrix of a quantum state by considering tensor contractions of the various parties with respect to a general finite symmetry group. Analogous to the entanglement entropy, the multi-trace can then be used to define "multi-trace measures", potential measures of multi-party entanglement. I will highlight how this structure allows for an equivalent geometric description in terms of q-point functions of twist operators for 2d CFTs and provide several examples. Using this construction I will calculate all three-point functions with genus 0 replica surfaces and demonstrate that their bulk duals, particular solutions of back reacted AdS3, preserve replica symmetry. Using these three-point function I will provide a method for how they can be combined together to construct candidate measures of higher party which satisfy several necessary conditions to also be bulk replica symmetry preserving. This leads naturally to ongoing work to fully categorize the space of all replica symmetry preserving multi-trace measures. Throughout the talk I will emphasize several related mathematical techniques and frameworks including: Riemann surfaces, handlebody orbifolds, three-manifold topology, Kleinian groups, automorphic functions, Schottky uniformization and semi-classical Liouville theory.
Based on:arXiv:2401.04236 J. Harper, T. Takayanagi and T. Tsuda Work in progress A. Gadde, J. Harper, and V. Krishna
Slide:
Masamich Miyaji (Nagoya University)
Time: 11:00 - 12:00
Title: Ensemble Averaging, Wormholes and Black Hole Information
Abstract: Classically, black holes are featureless objects. Yet quantum mechanically, it has a huge entropy given by the Bekenstein-Hawking formula. There has been a challenge to correctly capture this finite entropy in terms of low energy effective theory of quantum gravity. The recent remarkable progress in this direction comes from introducing Euclidean wormholes to semiclassical gravity path integral, which can reproduce unitary Page curve for the Hawking radiation, partially resolving the notorious black hole information paradox. On the other hand, the gravitational path integral with Euclidean wormholes does not correspond to a path integral of an Hermitian quantum system, but rather an ensemble average over such theories. Thus the entropy of Hawking radiation and the information recovery are mere averages, thus typical answer can have large deviations. We study these deviations of entropy, entanglement fidelity, and relative entropy, and found that they are exponential suppressed by the entropy of the black hole. I will also explain the difference between the random pure state and the entangled black hole after the Page time. If the time allows, I will also comment our primitive results on the black hole interior at late time using Euclidean wormholes.
Slide:
Kenta Suzuki (Rikkyo University)
Time: 12:00 - 12:30
Title: Gauge Symmetries and Conserved Currents in AdS/BCFT
Abstract: The AdS/BCFT correspondence is a simple variation of the ordinary AdS/CFT correspondence, which claims a duality between a quantum gravity in AdS spacetime with an end-of-the-world brane and a conformal filed theory defined on a spacetime with a boundary. This AdS/BCFT correspondence recently found interesting applications for black hole information paradox, as well as strong coupling dynamics of boundary conformal field theory (BCFT).
In this talk, we study massless vector perturbations in AdS spacetime with an end-of-the-world brane. By imposing U(1) preserving Neumann boundary condition on the end-of-the-world brane, we study their spectrum and discuss their implications for dual BCFT operators. The dual BCFT operators conserved currents and we show that such operators indeed satisfy the U(1) preserving conformal boundary condition. We also find several brane-tension-independent modes, which are understood as boundary-condition-independent modes from the dual BCFT point of view.
Slide:
Seok Kim (Seoul National University)
Time: 14:00 - 15:00
Title: Black holes, matrices and fermions
Abstract: I will reformulate the unitary matrix models for the thermal partition functions of gauge theories as multi-fermion quantum mechanics. I will also discuss its implications to holographic black hole physics.
Slide:
Matthew Roberts (APCTP)
Time: 16:00 - 16:30
Title: TBA
Abstract: TBA
Slide:
Minjae Cho (Princeton University)
Time: 16:30 - 17:00
Title: A (non-)worldsheet description of strings in AdS and flux compactifications
Abstract: For backgrounds with known exact worldsheet theory descriptions, ordinary string perturbation theory can be employed to study observables such as spectrum and scattering. However, the majority of interesting string backgrounds, including AdS and flux compactifications, lack such descriptions, posing challenges in understanding their stringy physics. Since these backgrounds are typically described as solutions to low-energy supergravity theory, having a string-theoretic counterpart to this field theory is desirable. In this talk, we discuss how string field theory provides such a framework, along with its limitations. Despite such limitations, we illustrate its practical utility in examining physical observables, particularly in examples such as AdS and flux compactifications.
Slide:
Vinay Malvimat (APCTP)
Time: 17:00 - 17:30
Title: A new genuine tripartite entanglement measure from reflected entropy
Abstract: We introduce a novel measure for genuine tripartite entanglement, with potential applications to many-body systems and holography. While the Markov gap, derived from the lower bound of reflected entropy, has emerged as a new measure, it fails to capture the genuine tripartite entanglement in any GHZ-type states. In contrast, our measure, based on the upper bound of reflected entropy, exhibits maximal values for GHZ states and remains non-vanishing for any state with tripartite entanglement. We illuminate its intriguing behavior in spin chain models, the Sachdev-Ye-Kitaev (SYK) model, and explore its implications in holography.
Slide:
Sumit Das (University of Kentucky)
Time: 10:00 - 11:00
Title: Notions of Entanglement of Internal Degrees of Freedom
Abstract: I will give an overview of some notions of entanglement of internal degrees of freedom and its connections with the holographic correspondence.
Slide:
Shan-Ming Ruan (YITP)
Time: 11:00 - 12:00
Title: A Half de Sitter Holography
Abstract: To explore de Sitter holography, we consider a half dS spacetime in which a time-like boundary encloses the bulk spacetime. By analyzing the holographic entanglement entropy in this space, we argue that gravity on a half dS_{d+1} is dual to a highly non-local field theory residing on the dS_d boundary. This non-locality illustrates the violation of the subadditivity of the holographic entanglement entropy. To probe the half de Sitter space, we glue it with a non-gravitational bath spacetime. However, we show that the quantum extremal surface is generally absent in this situation due to the fact that the island anchored on de Sitter space cannot dominate. By applying double holography, we further illustrate that the island should be smeared over de Sitter space and the entanglement wedge will include whole de Sitter gravity region.
Slide:
Hugo Camargo (GIST)
Time: 12:00 - 12:30
Title: Spread and Spectral Complexity in Quantum Spin Chains: From Integrability to Chaos
Abstract: Spread and spectral complexity have received attention in recent years within the study of the black hole interior in holography. In this talk I discuss them in the context of chaotic quantum many-body systems. I will highlight their characteristic features and compare them with those of the spectral form factor. Talk based on 2405.11254.
Slide:
Yasuaki Hikida (Kyoto University/YITP)
Time: 14:00 - 15:00
Title: Semi-classical saddles of three-dimensional gravity via holography
Abstract: We find out the complex geometries corresponding to the semi-classical saddles of three dimensional quantum gravity by making use of the known results of dual conformal field theory (CFT), which is effectively given by Liouville field theory. We examine both the cases with positive and negative cosmological constants. We determine the set of semi-classical saddles to choose from the homotopy argument in the Chern-Simons formulation combined with CFT results and provide strong supports from the mini-superspace approach to the quantum gravity. For the case of positive cosmological constant, partial results were already obtained in our previous works, and they are consistent with the current ones. For the case of negative cosmological constant, we identify the geometry corresponding a semi-classical saddle with three-dimensional Euclidean anti-de Sitter space dressed with imaginary radius three-dimensional spheres. The geometry is generically unphysical, but we argue that the fact itself does not lead to any problems.
Slide:
Victoria Martin (University of North Florida)
Time: 16:00 - 16:30
Title: The Wilson Spool and the Selberg zeta function
Abstract: In this talk, we introduce and relate two recently developed methods of calculating quantum gravitational effects of matter coupled to gravity: 1) The Wilson Spool of Castro, Coman, Fliss and Zukowski and 2) The generalized Selberg zeta function of Bagchi, Keeler, Martin and Poddar. The backgrounds that we will focus on are the BTZ black hole and the 3-sphere, with a massive, complex scalar field as the matter content. The chief strength of the Wilson Spool construction is that one can systematically compute quantum corrections to the partition function to all orders of Newton's constant, but it is only viable in 3 dimensions. The chief strength of the generalized Selberg construction is that it is simple and easily extendable to higher dimensional spacetimes and matter of general spin, but it only captures 1-loop results. Our hope is that combining these approaches is a strong step toward systematically calculating higher-order quantum gravitational effects in a more general setting.
Slide:
Kanghoon Lee (APCTP)
Time: 16:30 - 17:00
Title: The Schwarzschild Black Hole from Perturbation Theory to all Orders
Abstract: Applying the quantum field theoretic perturbiner approach to Einstein gravity, we compute the metric of a Schwarzschild black hole order by order in perturbation theory. Using recursion, this perturbative calculation can be carried out in de Donder gauge to all orders in Newton’s constant. The result is a geometric series which is convergent outside a disk of finite radius, and it agrees within its region of convergence with the known de Donder gauge metric of a Schwarzschild black hole. It thus provides a first all-order perturbative computation in Einstein gravity with a matter source, and this series converges to the known non-perturbative expression in the expected range of convergence.
Slide:
Jun Nishimura (KEK)
Time: 10:00 - 11:00
Title: The type IIB matrix model with "gauge-fixed" Lorentz symmetry and the emergence of (3+1)-dimensional space-time
Abstract: The type IIB matrix model is a promising candidate of nonperturbative formulation of superstring theory. However, the partition function is divergent due to the Lorentz symmetry, which is represented by a noncompact group. Recently we have proposed (arXiv:2404. 14045) that the partition function should be made well defined by "gauge -fixing" the Lorentz symmetry in a fully nonperturbative manner instead of introducing a Lorentz symmetry breaking cutoff as has been done conventionally. In this talk, we show that the gauge-fixed model is indeed quite different from the cutoff model and discuss the possibility of the emergence of (3+1)-dimensional expanding space-time in the gauge- fixed model.
Slide:
Masanori Hanada (Queen Marry University of London)
Time: 11:00 - 11:30
Title: Wave packet in gauge theory and emergent holographic geometry
Abstract: TBA
Slide:
Jack Holden (Tsinghua University)
Time: 11:30 - 12:00
Title: BPS black hole phase diagram and instanton condensation
Abstract: Using the superconformal index, we explore the phase diagram of 1/16-BPS black holes and provide evidence for a new saddle that dominates in some regions of the microcanonical ensemble. This new saddle is indicated by the condensation of instantons. We suggest ideas for the interpretation of the configuration in the field theory and the bulk, and a possible connection to the partially confined phase of Yang-Mills theories
Slide:
Ido Ben-Dayan (Ariel University)
Time: 12:00 - 12:30
Title: TBA
Abstract: TBA
Slide:
Vladimir Narovlansky (Princeton University)
Time: 14:00 - 15:00
Title: TBA
Abstract: TBA
Slide:
Christoph Uhlemann (VUB)
Time: 16:00 - 17:00
Title: TBA
Abstract: TBA
Slide:
Justin Kaidi (Kyushu University)
Time: 10:00 - 11:00
Title: Selection Rules Revisited
Abstract: Selection rules are one of the most basic manifestations of symmetry in a quantum mechanical system. Standard selection rules are useful for proving the vanishing of certain scattering amplitudes to all orders in perturbation theory. However, there are also examples of scattering amplitudes that vanish at low orders in perturbation theory, but are non-zero at higher orders. In this talk I will introduce a generalized notion of selection rules that can account for such phenomenon. These selection rules do not have an underlying symmetry explanation in field theory, but they do have one in string theory.
Slide:
Fedor Popov (New York University)
Time: 11:00 - 12:00
Title: Majorana Scars as Group Singlets
Abstract: In some quantum many-body systems, the Hilbert space breaks up into a large ergodic sector and a much smaller scar subspace. It has been suggested [arXiv:2007.00845] that the two sectors may be distinguished by their transformation properties under a large group whose rank grows with the system size (it is not a symmetry of the Hamiltonian). The quantum many-body scars are invariant under this group, while all other states are not. Here we apply this idea to lattice systems containing M Majorana fermions per site. The Hilbert space for N sites may be decomposed under the action of the O(N)×O(M) group, and the scars are the SO(N) singlets. For any even M there are two families of scars. One of them, which we call the η states, is symmetric under the group O(N). The other, the ζ states, has the SO(N) invariance. For M=4, where our construction reduces to spin-1/2 fermions on a lattice with local interactions, the former family are the N+1 η-pairing states, while the latter are the N+1 states of maximum spin. We generalize this construction to M>4. For M=6 we exhibit explicit formulae for the scar states and use them to calculate the bipartite entanglement entropy analytically. For large N, it grows logarithmically with the sub-system size. We present a general argument that any group-invariant scars should have the entanglement entropy that is parametrically smaller than that of typical states. The energies of the scars we find are not equidistant in general but can be made so by choosing Hamiltonian parameters. For M>6 we find that with local Hamiltonians the scars typically have certain degeneracies. The scar spectrum can be made ergodic by adding a non-local interaction term. We derive the dimension of each scar family and show the scars could have a large contribution to the density of states for small N.
Slide:
Sanjaye Ramgoolam (Queen Marry University of London)
Time: 12:00 - 12:30
Title: Holography, symmetry and statistics in matrix models
Abstract: Matrix variables arise as random variables in statistical models of real world matrix data as well as quantum mechanical degrees of freedom in quantum matrix models. The quantum matrix models arise in physically interesting sectors of quantum field theories with holographic duals which are string theories of quantum gravity. Polynomial functions of the matrix variables, invariant under appropriate symmetry groups, play a central role in both types of applications of matrix models. I will describe recent work exploiting the properties of polynomial functions of matrix variables of size N, invariant under conjugation by the symmetric group $ S_N $ of all permutations of $N$ objects. The counting of these functions for polynomial degree $k$ less than $N/2$ has a super-exponential growth as a function of $k$, which changes qualitatively at degree $k$ comparable to $(N \log N )/2$. These properties of the counting have striking implications in the thermodynamics of gauged permutation invariant matrix quantum harmonic oscillators. These include negative specific heat capacities in the micro-canonical ensemble. There is an in-equivalence between the micro-canonical and canonical ensembles at temperatures below a Hagedorn-like transition. These thermodynamic features have also been identified in multi-matrix models and tensor models with continuous gauge symmetries.
Slide:
Frank Ferrari (ULB)
Time: 14:00 - 15:00
Title: The UV Complete Jackiw-Teitelboim Quantum Gravity Theory
Abstract: I will discuss a rigorous definition of JT quantum gravity (in negative, zero or positive curvature), both from a discretized formulation and from a continuous point of view. In negative curvature, the usual Schwarzian theory appears to be a long-distance effective description, valid on distance scales much larger than the curvature length scale.
Slide:
Josephine Suh (KAIST)
Time: 16:00 - 17:00
Title: Correlators of the Volume Element in Gravity
Abstract: We discuss correlators of the volume element in gravity as fine-grained geometric observables that can capture the dynamics of holographic degrees of freedom underlying a quantum theory of gravity. We motivate our discussion by casting the Ryu-Takayanagi formula as an operational relationship between geometry and degrees of freedom in a bottom-up quantized theory of gravity. We then discuss aspects of the computation of correlators of volume via perturbation theory.
Slide:
Sumit Das (University of Kentucky)
Time: 9:30 - 10:00
Title: ANTAL JEVICKI : THE FIRST FIFTY YEARS
Slide:
Tamiaki Yoneya (Tokyo University)
Time: 10:00 - 10:30
Title: TBA
Slide:
Joao Rodrigues (University of Witwatersrand)
Time: 10:50 - 11:20
Title: TBA
Slide:
Julian Lee (Soongsil University)
Time: 11:20 - 11:40
Title: Decoding complexity of life
Slide:
Sera Cremonini (Lehigh University)
Time: 11:40 - 12:00
Title: From Black Holes to Superconductors
Slide:
Ines Aniceto (Southampton University)
Time: 13:30 - 13:50
Title: TBA
Abstract: TBA
Slide:
Robert de Mello Koch (Huzhou University)
Time: 13:50 - 14:10
Title: TBA
Slide:
Sanjaye Ramgoolam (Queen Marry University of London)
Time: 14:10 - 14:40
Title: TBA
Abstract: TBA
Slide:
Minjae Cho (Princeton University)
Time: 15:00 - 15:20
Title: A place for an undergrad
Kenta Suzuki (Rikkyo University)
Time: 15:20 - 15:50
Title: Gauge Symmetries and Conserved Currents in AdS/BCFT (2)
Abstract: As a continuation from my previous talk, we study several perturbations in AdS/BCFT correspondence.
In this talk, we study massive vector perturbations in AdS spacetime with an end-of-the-world brane. For this case, in general, there exists non-vanishing perpendicular components of the dual BCFT operator, even in the massless limit. We explain this difference between massless and massive perturbations from the point of view of the bulk gauge symmetry, or equivalently from different structure of equations of motion. We also discuss a generalization with p-form perturbations.
Slide:
Masanori Hanada (Queen Marry University of London)
Time: 16:10 - 16:40
Title: TBA
Abstract: TBA
Slide:
Aristomenis Donos (Durham University) [Online]
Time: 16:40 - 17:00
Title: TBA
Slide:
Igor Klebanov (Princeton University) [Online]
Time: 17:15 - 17:45
Title: TBA
Abstract: TBA
Slide:
Jeff Murgan (University of Cape Town) [Online]
Time: 17:45 - 17:50
Title: TBA
Slide: