Workshop on Low-dimensional Gravity and SYK Model
March 24 - 28, 2025
@Shinshu University
March 24 - 28, 2025
@Shinshu University
Invited Speakers
Takanori Anegawa
Norihiro IIzuka
Elba Alonso Monsalve*
Pratik Nandy
Sunil Sake
Kenta Suzuki
Seiji Terashima
Tomonori Ugajin
Masataka Watanabe
Masaki Tezuka
Jiuci Xu*
Jan Boruch*
(* online)
Schedule
March 24 Mon
10:30-12:00 Registration and Free Discussion
14:00-15:00 Masaki Tezuka
Sparse SYK and SYK-like models
Reducing the implementation cost of quantum mechanical models with holographic correspondence to gravity may pave the way for simulating quantum gravity by early fault-tolerant quantum computing. The sparse Sachdev-Ye-Kitaev (SYK) model reproduces essential features of the original SYK model while reducing the number of disorder parameters. In this talk, we discuss possibilities of further simplifications.
[1] Masaki Tezuka, Onur Oktay, Enrico Rinaldi, Masanori Hanada, and Franco Nori, Phys. Rev. B 107, L081103 (2023). (arXiv:2208.12098)
[2] Yoshifumi Nakata and Masaki Tezuka, Phys. Rev. Research 6, L022021 (2024).
[3] Masanori Hanada, Antal Jevicki, Xianlong Liu, Enrico Rinaldi, and Masaki Tezuka, JHEP05(2024)280.
[4] Pratik Nandy, Tanay Pathak, and Masaki Tezuka, Phys. Rev. B 111, L060201 (2025). (arXiv:2406.11969)
15:15-16:15 Pratik Nandy
Physics of tridiagonal Hamiltonians: lessons from Double-Scaled SYK model
The eigenvalues of Hermitian matrices are fundamental to understanding the statistical and dynamical properties of quantum systems. Traditionally, this involves diagonalizing the Hamiltonian, with the diagonal elements representing its eigenvalues. In this talk, I propose an alternative method: tridiagonalizing the Hamiltonian. Utilizing the Krylov space approach, I will explore the characteristics and distributions of the tridiagonal matrix elements, namely the Lanczos coefficients within the framework of random matrix theory and the Double-Scaled SYK model. The spectrum of the bulk Lanczos coefficients governs the late-time boundary physics and provides insights into the non-perturbative aspects of bulk gravity theory.
16:45-17:45 Contributed talks ( 30 min)
Kanato Goto
De Sitter Holography, –Should We See It from the Side or the Bottom?–
In this talk, we discuss the holographic duality between the double-scaled SYK model and quantum gravity in higher-dimensional de Sitter spacetime in the classical limit. Using "apparatus" defined with the operators in the SYK model, we appropriately define diffeomorphism-invariant physical quantities along a worldline of an observer in the de Sitter spacetime. Their two-point functions can reproduce Green’s function for a QFT on the d-dimensional de Sitter spacetime in the Bunch-Davies vacuum. In this talk, we discuss at the operator level why the physical observables defined on the worldline can be regarded as operators of the QFTon the de Sitter spacetime. Additionally, we study the relationship between the conventional dS/CFT approach, which uses quantum systems on the infinite past (future), and this new holographic principle based on an observer’s worldline.
Sergio Ernesto Aguilar Gutiérrez
Wormhole dynamics from partially entangled thermal states in the double-scaled SYK
We study the semiclassical thermodynamic properties, correlation functions, phase space solutions, and especially Krylov complexity in the double-scaled SYK (DSSYK) model with arbitrarily many particle chords. A key point in our analysis is defining partially entangled thermal states from the double-scaled algebra of observables of Lin. We generalize the Lanczos algorithm to evaluate both state and operator Krylov complexity at once and including finite temperature effects. The scrambling time in the operator Krylov complexity is encoded from an out-of-time-order correlator, and it displays both hyperfast growth, and submaximal chaos away from the semiclassical limit. We show that both state and operator Krylov complexity in the semiclassical limit correspond to a wormhole length in a two-sided AdS_2 black hole background with different boundary conditions. In particular, we recover sine-dilaton gravity Hamiltonians from constrained quantization in the path integral of the DSSYK model with matter. We develop several applications elucidating the bulk description of our results. These include: end-of-the-world branes; a universal speed limit on Krylov complexity; the mutual Krylov complexity for a bi-partition of the chord space; and the proper radial momentum of a point particle in AdS_2 space dual to the growth of Krylov operator complexity. We also propose a natural generalization of precursor operators in the DSSYK model to address the switchback effect in operator Krylov complexity.
19:00-21:00 Dinner
March 25 Tue
10:00-11:00 Jiuci Xu*
Quantum Algebra and Geometry from Chords in DSSYK
In this talk, I will explore the underlying quantum group structure from the chord algebra in the double-scaled SYK model. I will show how the one-particle states of chords furnish the discrete series representations of $U_q(\mathfrak{su}(1,1))$ and how the combinatorial chord rules naturally correspond to the fusion rules of these representations. In particular, I will show how the quantum 6j-symbol arises in crossing configurations and how this generalizes to correlation functions with arbitrary matter insertions. Finally, I will discuss how the chord dynamics give rise to a quantum bulk geometry with discrete radial direction that exhibits the quantum symmetry.
11:15-12:15 Masataka Watanabe
14:30-15:30 Takanori Anegawa
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 〜1/√D. This implies a timescale for thermal dissipation 〜√D. At high temperatures dissipation is predominantly due to one of the two quartic couplings.
16:00-16:40 Contributed talks ( 10 min)
Kazuyoshi Yano
Late time behavior of codimension-0 observables in JT gravity
Recently, complexity has been studied intensively as a holographic dual of bulk quantities which grows for exponentially late time. Originally, the volume of wormhole was proposed as a complexity dual in bulk, but it has been pointed out that wide classes of bulk observables are candidate for gravitational dual of complexity. In this study, we focus on the codimension-0 observables in JT gravity, which are considered to be bulk duals of complexity as well as volume of wormholes, and evaluate the late time behavior. We will present current status and future directions of our work in progress.
Shono Shibuya
Non-perturbative overlaps in JT gravity
TBA
Nanami Nakamura
Large double trace deformation and AdS traversable wormhole
In this presentation, we will discuss the relationship between large double trace deformations in CFTs and the AdS traversable wormholes. We argue that we can connect two disconnected AdS spaces at zero temperature via a wormhole by large double trace deformations. We support this idea by computing holographic correlation functions. We will also discuss how the causality looks like in such a model.
Michitaka Kohara
Brane cosmology from AdS/BCFT
In this presentation, I would like to talk about the dynamics of an End-of-the-World brane with a scalar field localized on it. There are three topics. One is about conformal dimension of the scalar field in dS/CFT context. Second, there is a kind of g-theorem in AdS/BCFT. And third topic is about brane world cosmology, which behaves non-trivially because of the scalar field. This talk is based on the recent collaborative work with Kanda, Takayanagi and Fujiki (arXiv:2501.05036).
March 26 Wed
10:00-11:00 Jan Boruch*
Modular-invariant random matrix theory and AdS3 wormholes
We develop a non-perturbative definition of RMT2: a generalization of random matrix theory that is compatible with the symmetries of two-dimensional conformal field theory. Given any random matrix ensemble, its n-point spectral correlations admit a prescribed modular-invariant lift to RMT2, which moreover reduce to the original random matrix correlators in a near-extremal limit. Central to the prescription is a presentation of random matrix theory in Mellin space, which lifts to two dimensions via the SL(2, Z) spectral decomposition employed in previous work. As a demonstration we perform the explicit RMT2 lift of two-point correlations of the GUE Airy model. We propose that in AdS3 pure gravity, semiclassical amplitudes for off-shell n-boundary torus wormholes with topology Sigma_{0,n} x S^1 are given by the RMT2 lift of JT gravity wormhole amplitudes. For the threeboundary case, we identify a gravity calculation which matches the RMT2 result.
Based on arxiv:2503.00101 with Gabriele di Ubaldo, Felix M. Haehl, Eric Perlmutter, and Moshe Rozali.
11:15-12:15 Seiji Terashima
Bulk reconstruction and subregion in AdS/CFT
We investigate how the quantum gravity theory emerges from the CFT (bulk reconstruction) when considering a subregion in the context of AdS/CFT. The study of subregions is crucial for understanding quantum gravity, particularly in areas such as black hole physics. Notably, we demonstrate that even in simple subregions, such as the AdS-Rindler patch, bulk local operators cannot be fully reconstructed—an outcome that contradicts conventional wisdom. Specifically, while a bulk reconstruction reproducing the two-point function exists, we show that higher-point functions, such as the three-point function, become ill-defined.
14:30-18:00 Free discussion
March 27 Thu (Starts at 9am)
9:00-10:00 Elba Alonso Monsalve*
Phase space of JT gravity with positive cosmological constant
We construct the classical phase space of Jackiw-Teitelboim (JT) gravity with positive cosmological constant on spatial slices with circle topology. We identify solutions not previously discussed in the literature, and find the phase space has many singular points and is not even Hausdorff. Nonetheless, it admits a group-theoretic description which is quite amenable to quantization.
10:15-11:15 Kenta Suzuki
Dimensional Reduction of the S^3/WZW Duality
Recently proposed duality relates the critical level limit $\hat{k} \to -2$ of $SU(2)_{\hat{k}}$ WZW models to a classical three-dimensional Einstein gravity on a sphere. In this talk, we propose a dimensional reduced version of this duality. The gravity side is reduced to a Jackiw-Teitelboim (JT) gravity on $S^2$ with a non-standard boundary term, or a BF theory with $SU(2)$ gauge symmetry. At least in low temperature limit, these two-dimensional gravity theories completely capture the original three-dimensional gravity effect. The CFT side is reduced to a certain complex Liouville quantum mechanics (LQM) with $SU(2)$ gauge symmetry. We also discuss a higher-spin generalization with $SU(N)$ gauge symmetry.
11:30-12:00 Contributed talk ( 30 min)
Tsunehide Kuroki
Properties of the wormhole-dominant phase in two-dimensional quantum gravity
We study the Hermitian one-matrix model modified by the double-trace interaction. It is known that the coupling for the double-trace interaction can control the weight for the microscopic wormholes if interpreting the matrix model as the lattice model of random surface; tuning the coupling to its critical value, the effect of wormholes become substantial to change the critical behavior of the pure 2D quantum gravity, which is characterized by a certain positive value of the string susceptibility. In the large-N limit, we calculate the continuum limit of the disk amplitude in which the wormhole effects are important. The resulting continuum disk amplitude is the same as that of the pure 2D quantum gravity. We also introduce the renormalized coupling for the double-trace interaction, and show that the newly introduced renormalized coupling can alter the renormalized bulk cosmological constant effectively.
14:30-15:30 Norihiro IIzuka
Genuine multi-entropy and holography
Is bipartite entanglement sufficient for holography? Through the analysis of the Markov gap, it is known that the answer is no. In this talk, we give a new perspective on this issue from a different angle using a multi-entropy.
15:45-16:15 Contributed talk ( 30 min)
Akihiro Miyata
Differences between black hole states in non-gravitating and gravitating baths
We study the distinguishability between black hole states in non-gravitating and gravitating baths using the PSSY model and the doubled PSSY model, which are important for understanding the behavior of black hole entropy and Page curves. By comparing the entanglement entropies of black holes in these cases, we find that the leading results are the same, but the sub-leading results differ due to differences in partially-connected replica saddles. We qualitatively investigate these differences using relative entropy. In this talk, I will explain the behavior of the relative entropy and its possible interpretation.
16:15-18:00 Free discussion
March 28 Fri
10:00-11:00 Sunil Sake
11:15-12:15 Tomonori Ugajin
14:30-18:00 Free Discussion
Registration
Registration form:
Venue
Shinshu University, Faculty of Science, Lecture Room 1
https://www.shinshu-u.ac.jp/faculty/science/others/access.html
(marked red in the campus map)
wifi: You can receive a guest account at the registration desk. You can also use eduroam at the venue.
Organizers
Kazumi Okuyama, Masamichi Miyaji, Tokiro Numasawa, Kotaro Tamaoka