Program
YITP workshop
January 20 - January 24, 2025
Yukawa Institute for Theoretical Physics, Kyoto University
All times shown are in JST (Japan Standard Time)
(† online speakers)
10:30-12:00 Seok Kim (Seoul National U.)
Black holes and trace relations
I will explain a version of the BPS black hole microstate construction in AdS/CFT from maximal super-Yang-Mills theory, in terms of supercharge cohomologies. The role of trace relations will be empasized, with explicit examples at low N. I will also explain how these constructions shed lights to the hairy black hole microstates.
1:15-2:45 Mitsuhiro Nishida (National Institute of Technology, Yuge College)
Black Hole Multi-Entropy Curves
We investigate the multi-partite entanglement structure of an evaporating black hole and its Hawking radiation by dividing the radiation into finer subsystems. Using the multi-entropy of these configurations, we define a black hole multi-entropy curve, which describes how the multi-entropy changes during the black hole evaporation. This black hole multi-entropy curve is a natural generalization of the Page curve since the multi-entropy reduces to the entanglement entropy for the bi-partite case. The multi-entropy curve keeps increasing in the early time. It reaches the maximum value at the multi-entropy time, which is later than the Page time, and starts to decrease. However, it does not decrease to zero at the end of the black hole evaporation. This non-zero value of the multi-entropy represents the secret entanglement between Hawking particles.
3:10-4:25 Kotaro Tamaoka (Nihon U.)
Interior of Black Hole from Pseudo Entropy
We study pseudo entropy, a generalization of von Neumann (entanglement) entropy to the (reduced) transition matrix, as a holographic probe of the black hole interior. We consider two setups where the holographic screen is located at (1) the asymptotic boundary (i.e., the conventional setup in AdS/CFT) and (2) inside the black hole. For setup (1), the pseudo entropy for certain subsystems corresponds to the so-called timelike entanglement. We propose that timelike entanglement serves as a direct probe of the black hole singularity. For setup (2), we observe that the pseudo entropy can significantly exceed the black hole entropy in general dimensions. We discuss possible connections to the non-isometric nature of the black hole interior and the non-Hermitian realization of such a holographic screen through TTbar-deformation.
10:30-12:00 Simon Lin (New York U. Abu Dhabi)
TTbar and the black hole interior
It has been conjectured that TTbar deformations of 2d CFTs are dual to AdS3 gravity at a finite radial cutoff. In this talk I will describe a sequence of generalized TT deformations that appears to push the cutoff boundary into the black hole interior. We verify our claim by showing an agreement between the flowed CFT energy levels and the bulk quasi-local energy on fixed radial slices. We also provide a bulk gravitational path integral whose saddles describe bulk spacetimes with finite radial cutoffs in the BH interior. This talk is based on an upcoming work with Shadi Ali Ahmad and Ahmed Almheiri.
1:30-3:00 Masamichi Miyaji (Yukawa Institute for Theoretical Physics, Kyoto U.)
Non-perturbative Overlaps in JT Gravity
The maximal volume of the black hole interior and the timeshift at the event horizon, are two fundamental degrees of freedom of the two-sided black hole, playing the crucial role of the structure of the event horizon and the interior. In this talk, we study properties of the non-perturbative states corresponding to the bulk fixed maximal volume state and fixed timeshift state. In particular, we study the non-perturbative overlap between these states and the time-evolved TFD state. From this overlap we can obtain the generating function \( \langle e^{-\alpha l}\rangle \) for the length \( l \) of geodesic timeslice and \( \langle e^{-\alpha \delta}\rangle \) for the timeshift, which display the dip-ramp-plateau behavior around the Heisenberg time. We find the expression for these generating functions in terms of the spectrum of the microscopic Hamiltonian, giving rise to new probes for chaotic properties of generic systems. Interestingly, we find in the naive limit \( \alpha \rightarrow 0 \), which has been associated to the length of the ER bridge, does not lead to sensible results but rather various pathologies including divergence, absence of classical linear growth and dip-ramp-plateau structure, indicating that we should keep the regularization finite in order to probe the bulk faithfully.
3:30-4:45 Gong Show
10:30-12:00 Ping Gao (Rutgers U.)†
More is different: a path from integrability to quantum chaos
We construct a new family of quantum chaotic models by combining multiple copies of integrable commuting SYK models. As each copy of the commuting SYK model does not commute with others, this construction breaks the integrability of each commuting SYK and the family of models demonstrates the emergence of quantum chaos. We study the spectrum of this model analytically in the double-scaled limit. As the number of copies tends to infinity, the spectrum becomes compact and equivalent to the regular SYK model. For finite d copies, the spectrum is close to the regular SYK model in UV but has an exponential tail in the IR. We identify the reciprocal of the exponent in the tail as a critical temperature \( T_c \) , above which the model should be quantum chaotic. \( T_c \) monotonically decreases as d increases, which expands the chaotic regime over the non-chaotic regime. We propose the existence of a new phase around \( T_c \) , and the dynamics should be very different in two phases. We further carry out numeric analysis at finite d, which supports our proposal. I will also comment on the implication of the critical temperature to future quantum simulations of quantum chaos and quantum gravity.
1:30-3:00 Janet Hung (Tsing Hua U.)
Space-time BCFT legos and RG flows
TBA
3:30-4:45 Akihiro Miyata (Yukawa Institute for Theoretical Physics, Kyoto U.)
Quantum error correction and black hole interior with a gravitating bath system
We investigate quantum error correction properties in a setup where a black hole is entangled with a gravitating bath, modeled by the doubled PSSY model. When treating errors in the bath system without considering gravitational back-reaction, the quantum error correction properties remain quantitatively similar to those of a non-gravitating bath. However, when we include gravitational back-reaction from errors (treated as local operators) in the bath system, we find that the resulting quantum error correction properties significantly deviate from both the non-gravitating case and the gravitating case without back-reaction. In this talk, we will discuss these differences and their implications.
5:00-6:30 Shira Chapman (Ben Gurion U. of Negev)†
Chaos in deformed SYK models - or - the fall of Krylov complexity?
The SYK model has attracted a lot of attention in recent years due to its maximal chaotic properties, its relation to two dimensional holography and to strange metals. Different signatures have been proposed to diagnose chaos in this model including the out of time ordered correlation functions (OTOCs) and Krylov complexity. Both quantities behave exponentially at early times in chaotic systems, giving rise to characteristic exponents: the Lyapunov exponent (for the OTOC) and the Krylov exponent (for Krylov complexity). In this talk, I will study both quantities in a class of relevant deformations of the SYK model. This will include deformations which interpolate between two regions of near-maximal chaos and deformations that become nearly-integrable at low temperatures. I will show both analytic and numerical results for the OTOC as well as the Krylov complexity. In all cases, I will show that the Krylov exponent upper-bounds the Lyapunov exponent. However, while the Lyapunov exponent can have non-monotonic behaviour as a function of temperature, in all studied examples the Krylov exponent behaves monotonically and has no distinctive features at the transition between the different chaotic regimes. This provides an example which disfavors the Krylov complexity as a diagnostic tool for quantum chaos in quantum mechanical systems.
10:30-12:00 Huajia Wang (KITS, U. of Chinese Academy of Sciences)†
Resurgence of the TTbar deformed partition function
TTbar deformation is a special solvable irrelevant deformations for two-dimensional CFTs. The deformed spectrum feature either a Hagedorn growth density of states or a finite UV cut-off depending on the signs, which hints at its stringy features and relevance to quantum gravity. While important insights into the deformed theories were obtained using perturbative analysis, in this talk we discuss the non-perturbative aspects via the resurgence analysis of perturbative expansion of the deformed partition function. We provide and verify the saddle-point origin of the resurgence observations, and discuss associated non-perturbative effects -- in particular its implications regarding the spectrum.
1:30-3:00 Sandip P. Trivedi (Tata Institute)†
JT gravity in deSitter Space and Its extensions
We will discuss the canonical quantisation of JT gravity in deSitter space. A path integral understanding of the resulting states, extensions of the JT theory and aspects connected to Holography, will also be discussed.
3:30-4:45 Takanori Anegawa (National Institute of Technology, Yonago College)
Dissipation in the \( 1/D \) expansion for planar matrix models
We consider the thermal behavior of a large number of matrix degrees of freedom in the planar limit. We work in 0+1 dimensions, with matrices, and use \( D \) as an expansion parameter. This can be thought of as a noncommutative large-\(D\) vector model, with two independent quartic couplings for the two different orderings of the matrices. We compute a thermal two-point correlator to \( O(1/D) \) and find that the degeneracy present at large \(D\) is lifted, with energy levels split by an amount \( \sim 1/\sqrt{D} \). This implies a timescale for thermal dissipation \( \sim \sqrt{D} \). At high temperatures dissipation is predominantly due to one of the two quartic couplings.
10:30-12:00 Pengfei Zhang (Fudan U.)†
Operator Size Dynamics: Theory & Application
Information scrambling emerges as a cornerstone in understanding thermalization in most closed quantum systems. In such systems, the initial information, though fully preserved under the unitary evolution, is scrambled from local physical objects into those highly non-local, which gives rise to quantum thermalization of simple operators in a sufficiently long time. In this talk, I will present our studies on operator size dynamics, focusing both on the development of fundamental theory in closed and open systems, as well as applications in quantum algorithms, such as quantum neural networks and classical shadow tomography.
1:30-3:00 Chong-Sun Chu (National Tsing Hua U.)
A proposal for quantum gravity and quantum mechanics of black
hole
We propose a quantum mechanical theory of quantum spaces described by large N noncommutative geometry as a model for quantum gravity. The theory admits fuzzy sphere and fuzzy ellipsoid as solution.
We show that these solutions reproduces precisely the horizon radius of a Schwarzschild black hole and a Kerr black hole. Moreover our quantum mechanical description gives rise to a set of microstates over these geometries, which reproduces precisely the Bekenstein-Hawking entropy of black hole. These results provide support that our proposed theory of quantum spaces is a plausible candidate for the theory of quantum gravity. Further progress and directions will be discussed.
3:15-4:30 Masaki Shigemori (Nagoya U.)
Multi-center solutions and effective superstrata
Multi-center solutions are solutions of 5D supergravity that describe bound states of branes in string theory. When all centers are 1/2-BPS, the multi-center solution represents a microstate of a black hole. In the first half of this talk, we show how multi-center solutions can describe D1-P supertubes in \( \mathrm{AdS}_{3} \times S^3 \). These are S-dual to the F1-P configurations studied recently by Martinec et al. In the second half, we discuss how multi-center solutions can be used to effectively describe the 6D microstate geometries called superstrata. This effective description allows us to study complicated superstrata configurations, which is not possible in 6D.
4:45-5:45 Sunil Sake (Yukawa Institute for Theoretical Physics, Kyoto U.)
Aspects of JT gravity in general spacetimes
We discuss the canonical quantisation of JT gravity with a general potential for dilation. We solve the constraint to find all the gauge invariant states and explore their properties. With a view to understanding the holography of de Sitter, we discuss cases of various potentials, corresponding to those which asymptote to either AdS, with a dS bubble inside, or asymptote to dS. We also discuss specific cases of pure AdS potential or pure dS potential everywhere and examine the issue of the Problem of Time.
15:30 Sergio Aguilar (Qubits and Spacetime Unit, Okinawa Institute of Science and Technology OIST)
Bridging Krylov and holographic complexity from the Double-Scaled SYK model and Sine Dilaton-Gravity: One-particle chords, proper momentum, and superadditivity
15:45 Kosei Fujiki (Yukawa Institute for Theoretical Physics, Kyoto U.)
dS/CFT from AdS/BCFT with a localized scalar field
16:00 Taishi Kawamoto (Yukawa Institute for Theoretical Physics, Kyoto U.)
A Strategy for Proving the Strong Eigenstate Thermalization Hypothesis
16:15 Huges Marcel (Graduate School of Science, Nagoya U.)
Lifting in the D1-D5 CFT
16:30 Wei-Hsiang Shao (National Taiwan U.)
Revisiting Hawking Radiation After Scrambling Time