Quantum thermalization, Hydrodynamics and Gravity

Jun 1, 2026, 8:50 AM → Jun 5, 2026, 8:00 PM Asia/Tokyo

Panasonic Auditorium, Yukawa Hall (YITP, Kyoto University)

Taishi Kawamoto (Yukawa Institute for Theoretical Physics (Kyoto University from next Aprile)), Masataka Watanabe (Nagoya University), Rathindra Nath Das, Shoki Sugimoto, Hideaki Nishikawa, Tadashi Takayanagi (Yukawa Institute for Theoretical Physics, Kyoto University)

Quantum thermalization, Hydrodynamics and Gravity

 

 

Schedule and Venue

June 1-5, 2026 

Panasonic Auditorium, Yukawa Hall, YITP, Kyoto University, Japan

---

Scope

Non-equilibrium physics, compared to the equilibrium counterpart, has so far remained as an obvious frontier in physics. While the topic is considered difficult due to the lack of systematic methods of analysis, developing such methods would be extremely desirable. It will not only deepen our view on the world around us but could even enable diverse industrial applications.

Recently, there has been a surge of new ideas and techniques across various areas of physics related to non-equilibrium phenomena such fields include quantum many-body chaos, hydrodynamics, and surprisingly, quantum gravity. Moreover, these ideas seem to be mutually connected, hinting at an emergence of a more systematic understanding, for example, in the name of effective field theories and black holes.

Despite this, there has only been a few attempts at unifying our understanding of non-equilibrium phenomena across various fields. The purpose of the proposed conference is to tackle this; to share ideas and foster collaboration among different fields, so that we will develop a new systematic and quantitative method of studying non-equilibrium physics.

---

Confirmed Speakers (invited)

Ryusuke Hamazaki (RIKEN)

Michal P. Heller (Ghent University and Jagiellonian University)

Alexander Altland (University of Cologne)

Bruno Bertini (University of Birmingham)

Hugo A. Camargo
 (National Center for Theoretical Sciences)

Masaru Hongo (Niigata University)

Jong Yeon Lee (University of Illinois Urbana-Champaign)

Chihiro Matsui (The University of Tokyo)

Shiraz Minwalla (Tata Institute of Fundamental Research)

Kazuaki Takasan (The University of Tokyo)

Anatoly Dymarsky (University of Kentucky) [online]

 

---

Contributing Talks and Poster 

 We will have contributing talks and Posters.  The registration for talks and posters are close in 25th March. (CLOSED. the registration without talks and visa is open up to 20th Apr. in JST time)

Program

	2026/6/1	2026/6/2	2026/6/3	2026/6/4		2026/6/5
	Monday	Tuesday	Wednesday	Thursday		Friday
	Chair: AM Sigimoto/PM Kawamoto	Chair: AM:Das/ PM Nishikawa	AM Watanabe/Kawamoto	Watanabe	Friday_Schedule	Chair: AM Nishikawa/ PM Sugimoto
9:20-9:30	Opening (Kawamoto)				9:20-9:30
9:30-10:00	Tutorial Lecture 1(Hamazaki)	Tutorial Lecture 3(Heller)	Invite 3 (Lee)	Invite 5 (Dymarsky)[online]	9:30-10:00	Invite 7 (Hongo)
10:00-10:30					10:00-10:30
10:30-11:00	Coffee	Coffee	Coffee	Coffee	10:30-11:00	Coffee
11:00-11:30	Invite 1 (Matsui)	Invite 2 (Camargo)	Invite 4 (Altland)	Invite 6 (Minwalla)	11:00-11:30	Contributing Talk 8(Keisuke Fujii)
11:30-12:00					11:30-12:00	Short break
12:00-12:15	Short break	Short break	Group Photo	Short break	12:00-12:15	Invite 8 (Bertini)
12:15-12:45	Contributing Talk 1(Masaya Kunimi)	Contributing Talk 3(Michael Blake)	Lunch	Contributing Talk 5(Shuta Ishigaki)	12:15-12:45
12:45-14:30	Poster Instllation	Lunch		Lunch	12:45-14:30	Lunch
	Lunch
14:30-15:00	Tutorial Lecture 2 (Heller)	Tutorial Lecture 4 (Hamazaki)	Poster　2 (@Y306)	Invite 9(Takasan)	14:30-15:00	Contributing Talk 9(Tanay Pathak)
15:00-15:30			Poster　2 (@Y306)		15:00-15:30	Contributing Talk 10(Teruaki Nagasawa)
15:30-16:00	Coffee	Coffee	Poster　2 (@Y306)	Coffee	15:30-15:45	Shortbreak
16:00-16:30	Contributing Talk 2(Shin Nakamura)	Contributing Talk 4(Yuuya Chiba)	Poster　2 (@Y306)	Contributing Talk 6(Sumiran Pujari)	15:45-16:15	Contributing Talk 11(Shozo Yamada)
16:30-17:00		Poster 1 (@Y206)		Contributing  Talk7 (Jian Xian Sim)	16:15-16:25	Closing (Kawamoto)
17:00-17:30		Poster 1 (@Y206)	Banquet　at U. Cafeteria		17:00-17:30
17:30-18:00		Poster 1 (@Y206)	Banquet　at U. Cafeteria		17:30-18:00
18:00-18:30		Poster 1 (@Y206)	Banquet　at U. Cafeteria		18:00-18:30

---

Organizers

Taishi Kawamoto (Kyoto University) 
Masataka Watanabe (The University of Tokyo) 
Shoki Sugimoto (The University of Tokyo) 
Rathindra Nath Das (Weizmann, MIT, Würzburg) 
Hideaki Nishikawa (RIKEN center of Quantum Computing) 
Tadashi Takayanagi (YITP)

---

About this workshop

This workshop is "YITP International Workshop Led by Young Researchers" supported by YITP.   Also this workshop is supported by Taishi Kawamoto with The Hakubi Project in Kyoto University.

---

Acknowledgement

If your research was benefitted from discussions/talks/new collaborations during this workshop, please acknowledge YITP.

Example:
The authors thank Yukawa Institute for Theoretical Physics at Kyoto University.
 

 

Mon, June 1

8:50 AM Registraton

Participants attending the banquet are asked to pay 1,000 yen at the reception.

We would appreciate it if you could prepare a 1,000-yen bill in advance, as we cannot guarantee that change will be available.

Opening

Tutorial Lecture: Thermalization and its breakdown in closed quantum systems

Recent developments of quantum simulators and quantum computers have enabled us to realize and engineer quantum many-body dynamics in a highly controllable manner. This has motivated researchers to revisit the foundations of statistical mechanics from quantum mechanics, a subject that dates back to von Neumann's seminal work about a century ago. In this tutorial talk, I will give an introductory review of non-equilibrium dynamics in quantum many-body systems.

In the first part, I will review thermalization and its breakdown in closed quantum systems [1,2]. After reviewing how thermalization of pure states is justified by the eigenstate thermalization hypothesis (ETH), I will discuss the relationship between ETH, nonintegrability, and symmetry. I will then overview more exotic mechanisms for the breakdown of thermalization, such as many-body localization, quantum many-body scars, and Hilbert-space fragmentation. Finally, I will review how the second law of thermodynamics in closed systems, which cannot be understood solely in terms of thermalization, can be justified in quantum many-body systems.

In the second part, I will consider relaxation and its breakdown in open quantum systems, including systems subject to quantum measurement [3]. I will first explain the basics of measurement theory and the Gorini-Kossakowski-Sudarshan-Lindblad (GKSL) equation. Then, steady-state structures and relaxation toward them will be discussed from the viewpoint of Liouvillian spectra and strong symmetries. Finally, I will discuss measurement-induced transitions of quantum trajectories from the viewpoint of purification and the Lyapunov spectrum.

[1] L. D’Alessio et al., Advances in Physics 65.3 (2016).
[2] S. Moudgalya et al., Rep. Prog. Phys. 85 086501 (2022).
[3] RH, K Mochizuki, H Oshima, and Y Fuji, PTEP, ptag055 (2026).

Convener: Ryusuke Hamazaki (RIKEN)

Day_1_Hamazaki_1.mp4

YITP_thermalization_hamazaki - 濱崎立資.pdf

10:30 AM Coffee Break

1 Quantum many-body scars and symmetry-associated topological properties

Recent progress in statistical physics has revealed the emergence of nonthermal phenomena in otherwise ergodic systems. Quantum many-body scars (QMBS) are known to be one of the central ingredients underlying such atypical behaviors.
QMBS often appear as special eigenstates of ergodic quantum systems, forming a small but nontrivial invariant subspace. In this talk, we discuss the mathematical structure that stabilizes such subspaces under dynamics. At the same time, we demonstrate that the scar subspace can inherit properties of the underlying ground state, with particular emphasis on symmetry-associated topological properties.
This talk is based on recent joint work (arXiv:2512.11216).

Speaker: Chihiro Matsui (The University of Tokyo)

2026Jun01 - Chihiro Matsui.pdf

Day_1_Matsui.mp4

12:00 PM Short break

2 Systematic construction of asymptotic quantum many-body scar states and their relation to supersymmetric quantum mechanics

Quantum many-body scar (QMBS) states, which are special energy eigenstates that violate the eigenstate thermalization hypothesis in nonintegrable systems, have attracted much attention. Recently, asymptotic quantum many-body scar (AQMBS) states, which are closely related to QMBS states, have been proposed [1]. AQMBS states exhibit nonergodic behavior because their energy variance vanishes in the thermodynamic limit. Moreover, AQMBS states are related to Nambu-Goldstone modes, indicating a connection between thermalization in isolated quantum systems and spontaneous symmetry breaking [2]. However, existing constructions of AQMBS states are heuristic, and a systematic method for constructing them has not yet been established. In this work, we propose a systematic framework for constructing AQMBS states [3]. Within this framework, we assume a restricted spectrum-generating algebra [4,5], a symmetry-based formalism [6], and a specific structure of the Hamiltonian. Under these assumptions, AQMBS states arise as low-energy gapless excitations of a parent Hamiltonian whose ground states are QMBS states. Furthermore, we find that the algebraic relations of N=2 supersymmetric quantum mechanics naturally emerge in systems satisfying these assumptions. In this seminar, I will present the details of the method and its applications to several models.
[1]L. Gotta et al, Phys. Rev. Lett. 131, 190401 (2023).
[2]J. Ren et al., Phys. Rev. B 110, 245101 (2024).
[3]MK, Y. Kato, and H. Katsura, Phys. Rev. Res. 7, 043107 (2025).
[4]D. K. Mark et al, Phys. Rev. B 101, 195131 (2020).
[5]S. Moudgalya et al, Phys. Rev. B 102, 085140 (2020).
[6]N. O'Dea et al, Phys. Rev. Res. 2, 043305 (2020).

Speaker: Masaya Kunimi (Tokyo University of Science)

Day_1_Kunimi.mp4

slide_Kunimi - 國見昌哉.pdf

12:45 PM Lunch

Tutorial Lecture: Near-equilibrium dynamics of quantum fields

Convener: Michal P. Heller (Ghent University and Jagiellonian University)

3:30 PM Coffee Break

3 Fluctuation-response inequality and gravity

The fluctuation–response inequality (FRI), proposed by Dechant and Sasa, is a general relation between fluctuations and responses in nonequilibrium systems. For instance, the FRI states that the ratio of the effective temperature to the differential mobility of a test particle in a thermal bath is a non-decreasing function of the particle’s velocity. In this work, we compute both the effective temperature and the differential mobility of a probe in a thermal bath using gauge/gravity duality in various gravitational backgrounds. We find that the FRI is satisfied in most setups consistent with superstring theory, with the exception of a few ill-defined cases. We also discuss how the geometry on the gravity side is constrained by the FRI.

Speaker: Shin Nakamura (Chuo University)

Tue, June 2

Tutorial Lecture: Far-from-equilibrium dynamics of quantum fields

Convener: Michal P. Heller (Ghent University and Jagiellonian University)

10:30 AM Coffee Break

4 Quantum Signatures of Chaos from Free Probability

Free probability theory provides a rigorous framework for non-commutative random variables with free independence, and is the natural language for operator algebras in quantum mechanics. It has recently been explored as a tool for modeling aspects of quantum chaos, thermalization, and scrambling in regimes where random‑matrix or mean‑field behavior is expected. In this talk, I will provide an introduction to free probability theory and I will motivate and discuss its recent applications to describe quantum mixing in terms of emergent free independence between quantum observables in terms of operator statistics in models such as the mixed-field Ising, the q=2,4 SYK models and the RP model. This talk is based on 2503.20338 and 2506.04520.

Speaker: Hugo A. Camargo (National Center for Theoretical Sciences, Physics Division)

Day_2_Camargo.mp4

V4Condensed_Camargo_YITP_June2026.pdf

12:00 PM Short break

5 A holographic prescription for dissipative hydrodynamical actions and horizon symmetries

The last decade has seen significant interest in dissipative hydrodynamical actions in the Schwinger-Keldysh formalism. However there remain very few examples where such actions can be explicitly constructed. I will present a novel prescription that allows, for the first time, one to consistently compute such actions for holographic quantum field theories in general bulk dimension. The explicit construction of such actions allows us to test conjectured relations between hydrodynamical actions and quantum chaos – in particular I will discuss to what extent such actions realise horizon symmetries previously argued for by Knysh, Liu & Pinzani-Fokeeva.

Speaker: Michael Blake (University of Bristol (UK))

12:45 PM Lunch

Tutorial Lecture: Relaxation and its breakdown in open quantum systems: Tutorial Lecture

Recent developments of quantum simulators and quantum computers have enabled us to realize and engineer quantum many-body dynamics in a highly controllable manner. This has motivated researchers to revisit the foundations of statistical mechanics from quantum mechanics, a subject that dates back to von Neumann's seminal work about a century ago. In this tutorial talk, I will give an introductory review of non-equilibrium dynamics in quantum many-body systems.

In the first part, I will review thermalization and its breakdown in closed quantum systems [1,2]. After reviewing how thermalization of pure states is justified by the eigenstate thermalization hypothesis (ETH), I will discuss the relationship between ETH, nonintegrability, and symmetry. I will then overview more exotic mechanisms for the breakdown of thermalization, such as many-body localization, quantum many-body scars, and Hilbert-space fragmentation. Finally, I will review how the second law of thermodynamics in closed systems, which cannot be understood solely in terms of thermalization, can be justified in quantum many-body systems.

In the second part, I will consider relaxation and its breakdown in open quantum systems, including systems subject to quantum measurement [3]. I will first explain the basics of measurement theory and the Gorini-Kossakowski-Sudarshan-Lindblad (GKSL) equation. Then, steady-state structures and relaxation toward them will be discussed from the viewpoint of Liouvillian spectra and strong symmetries. Finally, I will discuss measurement-induced transitions of quantum trajectories from the viewpoint of purification and the Lyapunov spectrum.

[1] L. D’Alessio et al., Advances in Physics 65.3 (2016).
[2] S. Moudgalya et al., Rep. Prog. Phys. 85 086501 (2022).
[3] RH, K Mochizuki, H Oshima, and Y Fuji, PTEP, ptag055 (2026).

Convener: Ryusuke Hamazaki (RIKEN)

Day_2_Hamazaki_2.mp4

YITP_thermalization_hamazaki - 濱崎立資.pdf

3:30 PM Coffee Break

6 Second law of thermodynamics in closed quantum many-body systems

The second law of thermodynamics for adiabatic operations --- constraints on state transitions in closed systems under external control --- is one of the fundamental principles of thermodynamics. On the other hand, recent studies of thermalization have established that even pure quantum states can represent thermal equilibrium. However, pure quantum states do not satisfy the second law in that they are not passive, i.e., work can be extracted from them if arbitrary unitary operations are allowed, and that various entropy formulas, such as the von Neumann entropy, deviate from thermodynamic entropy in such states. It therefore remains unresolved how thermal equilibrium represented by a pure quantum state can be reconciled with thermodynamics. Here, based on our key quantum-mechanical notions of thermal equilibrium and adiabatic operations, we address the emergence of the second law of thermodynamics in closed quantum many-body systems. We first introduce infinite-observable macroscopic thermal equilibrium (iMATE); a quantum state, including pure states, is said to represent iMATE if the expectation values of all additive observables, which correspond to additive quantities in thermodynamics, agree with their equilibrium values. We also introduce a macroscopic operation as unitary evolution generated by a time-dependent additive Hamiltonian, which is regarded as corresponding to adiabatic operations. Employing these concepts, we show Planck's principle: no extensive work can be extracted from any quantum state representing iMATE through any macroscopic operations with the operation times independent of the system size. Furthermore, we introduce a quantum-mechanical form of entropy density such that it agrees with thermodynamic entropy density for any quantum state representing iMATE. We then prove the law of increasing entropy: for any initial state representing iMATE, this entropy density cannot be decreased by any macroscopic operations with the operation times independent of the system size, followed by a relaxation process governed by a time-independent Hamiltonian. Our theory thus proves two different forms of the second law, which are quantum mechanically inequivalent to each other, and demonstrates how thermodynamics emerges from quantum mechanics by adopting macroscopically reasonable classes of observables, equilibrium states, and operations. This presentation is based on arXiv:2602.06657.

Speaker: Yuuya Chiba (RIKEN)

0602_YuuyaChiba_SecondLaw - Yuuya Chiba.pdf

Day_2_Chiba.mp4

Poster Talk: Poster Talk 1

Poster Talk

Abstract

Wed, June 3

7 From Strong-to-Weak Symmetry Breaking to Hydrodynamics in Open Quantum Systems

Hydrodynamics in open quantum systems has recently been proposed to admit a new interpretation: hydrodynamic modes can be viewed as Goldstone modes associated with strong-to-weak spontaneous symmetry breaking (SWSSB) [1]. However, an important conceptual gap remains. SWSSB is defined using nonlinear, information-theoretic diagnostics of mixed states, whereas hydrodynamics is observed through linear response and equal-time correlation functions. In particular, a nontrivial static charge structure factor was identified in Ref. [1] as an additional ingredient linking SWSSB to hydrodynamics, but this point has often been obscured in subsequent discussions. In this talk, I will clarify this connection. I will show how SWSSB constrains the static structure factor, thereby identifying a necessary bridge between nonlinear mixed-state order and physically observable hydrodynamic behavior [2]. I will then present a hydrodynamic Nambu-Goldstone theorem [3] for charge-conserving Lindbladians, showing under what conditions conserved charges in open quantum dynamics necessarily give rise to long-lived hydrodynamic modes. Together, these results provide a sharper framework for understanding when and how hydrodynamics emerges in open quantum systems.
[1] O Ogunnaike, J Feldmeier, JY Lee, PRL 131, 220403 (2023)
[2] JY Lee, arXiv:2605.05288
[3] JY Lee, ongoing work (2026)

Speaker: Jong Yeon Lee (University of Illinois Urbana-Champaign)

Day_3_Lee.mp4

Slide_JYL - Jong Yeon Lee.pdf

10:30 AM Coffee Break

8 Field Theory in Circuit Dynamics

Recent years have witnessed major advances in the understanding of quantum circuit dynamics — progress essential to the success of the field as quantum hardware increasingly moves beyond the reach of classical simulation. The emerging “theory” of quantum devices is largely discrete in character, with prevalent concepts drawn from statistical mechanics, tensor networks, or the combinatorics of random matrices. At the same time, quantum field theory — physics’ established lingua franca for the understanding of complex many-body systems — remains strangely underrepresented, raising the question of why this is so.

In this talk we discuss two paradigmatic aspects of circuit dynamics, thermalization toward ergodic late-time regimes and entanglement generation, to suggest some answers. We argue that quantum field theory provides both access to system classes that may be difficult to approach otherwise and insight into non-perturbative aspects of irreversible circuit evolution. We further argue that these aspects can be relevant to the understanding of realistic hardware, substantiating this claim through comparison with exact diagonalization results for small-system prototypes.

Speaker: Alexander Altland (University of Cologne)

Day_3_Altland.mp4

FieldTheoryCircuits - Alexander Altland.pdf

Group Photo (even it is rainy)

12:20 PM Lunch

Poster Talk: Poster 2

Poster Talk

Abstract

Banquet

@ U.Cafeteria
https://www.kyoto-u.ac.jp/en/access/north-campus-map

Thu, June 4

9 Holographic Krylov complexity (ONLINE)

I will discuss how the Krylov space method can be formulated for holographic theories, and how it can help to define a dual holographic description for non-holographic systems.

Speaker: Anatoly Dymarsky (University of Kentucky)

Day_4_Dymarsky.mp4

10:30 AM Coffee Break

10 Level Rank Duality in Quantum Mechanics

We study Chern Simons theories coupled to massive matter fields in an energy regime in which the kinetic energy of all particles is small compared to their rest masses.
In this limit, the dynamics is described by a non relativistic Schrodinger equation. We present an explicit formulation of this Schrodinger equation. In situations in which the two Chern Simons theories are related by conjectured
Bose Fermi dualities, we find an explicit linear transformation of wave functions, that turns one Schrodinger equation into another, `proving' the duality in the limit under study.

Speaker: Shiraz Minwalla (Tata Institute of Fundamental Research)

Day_4_Minwalla.mp4

YITP-Chern-Simons26 - Shiraz Minwalla.pdf

12:00 PM Short Break

11 Quantum Mpemba effect in holography

The Mpemba effect is a counterintuitive phenomenon in which hotter substances cool down faster. This phenomenon can be observed under limited conditions. On the other hand, the quantum Mpemba effect (QME) is quantum analogue of it by replacing the temperature with other quantities. The QME may have various origins but it is helpful if we can understand its common mechanism. To shed light on it, we investigate the emergence of the QME by analyzing time evolution in the bottom-up holographic superfluid model. Our results indicate that the QME widely occurs in the holographic superfluid model under the probe limit.

Speaker: Shuta Ishigaki (Shanghai University)

12:45 PM Lunch

12 Active Matter, KPZ, and (possibly) Gravity

In this talk, I will discuss two recent developments in nonequilibrium phenomena in condensed matter physics and then touch on possible connections to quantum gravity.

The first topic is quantum active matter. Active matter consists of self-propelled constituents that consume energy locally and exhibit collective behavior far from equilibrium [1]. Although active matter has mostly been studied in classical soft-matter systems, recent work has begun to extend its concepts to quantum many-body systems. I will introduce our results on non-Hermitian quantum many-body systems that share key features with active matter [2,3].

The second topic is the emergence of the Kardar-Parisi-Zhang (KPZ) universality class in quantum spin chains. KPZ universality was originally found in stochastic classical nonequilibrium dynamics, such as interface growth. It is therefore striking that KPZ scaling can appear in the deterministic time evolution of isolated quantum systems [4]. I will present our numerical study showing that KPZ universality appears in certain two-point correlation functions, rather than in all aspects of the dynamics [5]. In this sense, it may be viewed as a partial, yet definite, emergence of KPZ physics.

I will conclude the talk by briefly commenting on possible connections to quantum gravity. In these comments, I will touch on links between non-Hermitian systems and curved-space physics [6], as well as a proposed JT/KPZ correspondence involving double-scaled SYK, open ASEP, and KPZ correlations [7].

References:
[1] e.g., M. C. Marchetti, J. F. Joanny, S. Ramaswamy, T. B. Liverpool, J. Prost, M. Rao, and R. A. Simha, Rev. Mod. Phys. 85, 1143 (2013).
[2] K. Adachi, KT, and K. Kawaguchi, Phys. Rev. Research 4, 013194 (2022).
[3] KT, K. Adachi, and K. Kawaguchi, Phys. Rev. Research 6, 023096 (2024).
[4] M. Ljubotina, M. Znidaric, and T. Prosen, Phys. Rev. Lett. 122, 210602 (2019).
[5] K. A. Takeuchi, KT, O. Busani, P. L. Ferrari, R. Vasseur, and J. De Nardis, Phys. Rev. Lett. 134, 097104 (2025).
[6] C. Lv, R. Zhang, Z. Zhai, and Q. Zhou, Nat. Commun. 13, 2184 (2022).
[7] M. Watanabe, arXiv:2511.02529 (2025).

Speaker: Kazuaki Takasan (The University of Tokyo)

Day_4_Takasan.mp4

YITP_gravity_2026 for sharing - Kazuaki Takasan.pdf

3:30 PM Coffee Break

13 Complex-CFT governed pseudocriticality in quantum spin chains

Weak first-order pseudocriticality with approximate scale invariance has been observed in a variety of settings, including the intriguing case of deconfined criticality in 2+1 dimensions. Recently, this has been interpreted as extremely slow flows ("walking behavior") for real-valued couplings in proximity to a bona fide critical point with complex-valued couplings, described by a complex conformal field theory (CFT). Here we study an SU(N) generalization of the the Heisenberg antiferromagnet, which is a familiar model for deconfined criticality in 2+1 dimensions. We show that in 1+1 dimensions the model is located near a complex CFT, whose proximity can be tuned as a function of N. We employ state-of-the-art quantum Monte Carlo simulations for continuous N along with an improved loop estimator for the Rényi entanglement entropy based on a nonequilibrium work protocol. These techniques allow us to track the central charge of this model in detail as a function of N, where we observe excellent agreement with CFT predictions. Notably, this includes the region N>2, where the CFT moves into the complex plane and pseudocritical drifts enable us to recover the real part of the complex central charge with remarkable accuracy. Since the present model with N=3 is also equivalent to the spin-1 biquadratic model, our work sheds new light on the dimerized phase of the spin-1 chain, demonstrating that it is pseudocritical and proximate to a complex CFT.

Speaker: Sumiran Pujari (Indian Institute of Technology Bombay)

2026_yitp_kyoto - Sumiran Pujari.pdf

Day_4_Pujari.mp4

14 Resonance-Suppression Principle for Prethermalization beyond Periodic Driving (https://arxiv.org/abs/2603.21540)

Non-equilibrium dynamics of strongly and rapidly driven quantum many-body systems is poorly understood beyond periodic driving, where heating is exponentially slow in the drive frequency (Floquet Prethermalization). In contrast, non-periodic drives were found to exhibit widely different heating scalings with no unifying principle. This work identifies a resonance-suppression principle governing slow heating up to a prethermal lifetime τ∗: When the drive's spectral arithmetic structure restricts multiphoton resonances, τ∗ is controlled by low-frequency spectral suppression. The principle distinguishes (i) Single-photon suppression, quantified by a low-frequency suppression law f(Ω) for the drive's Fourier Transform weight near Ω=0, from (ii) Multi-photon suppression, where nested commutators remain controlled if exceptional arithmetic structure satisfies a subadditive property. Remarkably, if multi-photon suppression holds, τ∗ scaling with drive speed λ is governed by f(Ω). This law of τ∗ is found through a small-divisor mechanism in this work's iterative rotating frame scheme. Multi-photon suppression breakdown separates λ-scaling of τ∗ in linear response and non-perturbative theory, shown by a case study of Quasi-Floquet driving. The principle is applied to (i) Resolve inconsistencies in literature on non-periodic driving, and (ii) Provide design principles for engineering prethermal phases of matter in programmable quantum simulators, exemplified by new non-periodic `Factorial' drives with tunable τ∗.

Speaker: Jian Xian Sim (Center for Quantum Technologies Singapore)

Day_4_Xian.mp4

Final Version Talk for Prethermalization - Jian Xian Sim.pdf

Fri, June 5

15 Modern field-theoretical approaches to hydrodynamics

Hydrodynamics is a universal low-energy effective field theory describing the macroscopic real-time dynamics of many-body systems. Over the past decade, remarkable progress has been made in reformulating hydrodynamics from the viewpoint of quantum field theory. In this talk, I will review these developments, focusing on both the imaginary-time and real-time formalisms of hydrodynamics and their connections to modern effective field theory.

Speaker: Masaru Hongo (Niigata Universiity)

10:30 AM Coffee Break

16 Hydrodynamic attractor in ultracold atoms

The hydrodynamic attractor is a concept that describes universal equilibration behavior in which systems lose microscopic details before hydrodynamics becomes applicable. We propose a setup to observe hydrodynamic attractors in ultracold atomic gases, taking advantage of the fact that driving the two-body s-wave scattering length causes phenomena equivalent to isotropic fluid expansions. We specifically consider two-component fermions with contact interactions in three dimensions and discuss their dynamics under a power-law drive of the scattering length in a uniform system. By explicit computation, we derive a hydrodynamic relaxation model. We analytically solve their dynamics and find the hydrodynamic attractor solution. Our proposed method using the scattering length drive is applicable to a wide range of ultracold atomic systems, and our results establish these as a new platform for exploring hydrodynamic attractors.

Speaker: Keisuke Fujii (Institute of Science Tokyo)

Day_5_Fujii.mp4

KF_202606_Kyoto - Kei F.pdf

11:30 AM Short Break (15min.)

17 Exact many-body dynamics in quantum circuits via space-time duality

In recent years, quantum circuits have emerged as useful effective models to understand generic quantum many-body dynamics, and as concrete platforms for quantum simulation. The most appealing feature of these systems is that, contrary to generic many-body systems in continuous time, the dynamics of quantum circuits are sometimes amenable to analytical treatment. In the talk I will present a fruitful route to achieve this goal based on imposing a duality symmetry between space and time. I will review how this symmetry allows to fully characterise interesting features of quantum many-body dynamics, such as entanglement spreading and operator growth, and examine its implications. I will then discuss how to systematically weaken this symmetry while retaining (some) solvability, and how an exchange of space and time can help characterising general aspects of quantum many-body dynamics.

Speaker: Bruno Bertini (University of Birmingham)

Day_5_Bertini.mp4

Kyoto - Bruno Bertini.pdf

12:45 PM Lunch

18 Mixed-State Entanglement in a Minimal Model of Quantum Chaos

We study the dynamics of mixed-state entanglement in a minimal model of quantum chaos, the kicked field Ising model, using a class of solvable initial states. By combining the replica trick with the space-time duality of the model, we show that the exact spectrum of the partially transposed reduced density matrix is flat at early times. This leads to exact relations between entanglement negativity, odd entropy and R´enyi mutual information. Extensive numerical simulations also demonstrate that this relation remains quantitatively valid for generic initial states and at late times, motivating the conjecture that it holds in general. Our results indicate that this relation extends beyond the present minimal model to more general Ising-type quantum spin chains.

Speaker: Tanay Pathak (Kyoto University)

Day_5_Pathak.mp4

TP_Talk_YITP_2026 - tanay pathak.pdf

19 An Observer-Based Approach to Thermalization

Thermalization and gravity have one thing in common: they do not align well with quantum mechanics. One possible explanation for this is that these phenomena are macroscopic rather than microscopic. So, what does it mean to be 'macro'? Furthermore, these phenomena may be characterized by the fact that they are described as relative to each observer. In order to address these questions, we will discuss a mathematical framework based on the concept of observer-dependent entropy. In particular, we will discuss how the increase in entropy occurs.

Speaker: Teruaki Nagasawa (Kanazawa University)

Day_5_Nagasawa.mp4

Thermalization - 長澤輝明.pdf

3:30 PM Short Break (15min)

20 Tunable many-body burst in isolated quantum systems

While thermalization in isolated quantum many-body systems can be explained by the eigenstate thermalization hypothesis, its process can be nonmonotonic depending on an initial state. In this talk, we propose a numerical method to construct a low-entangled initial state that creates a “burst”——a transient deviation of an expectation value of an observable from its thermal equilibrium value——at a designated time. Our method utilizes the density matrix renormalization group algorithm to find such a state within the matrix product state manifold. We apply this method to demonstrate that a burst of magnetization can be realized for a nonintegrable mixed-field Ising chain on a timescale comparable to the onset of quantum scrambling. Contrary to the typical spreading of information in this regime, the created burst is accompanied by a slow or even negative entanglement growth. Analytically, we employ a local random quantum circuit to show that a burst becomes probabilistically rare after a long time. Our results suggest that a nonequilibrium state is maintained for an appropriately chosen initial state until scrambling becomes dominant. Due to the low-entangled nature of the initial state, our predictions can be tested with programmable quantum simulators. Ref: S. Yamada, A. Hokkyo, and M. Ueda, arXiv:2602.09665 [quant-ph] (2026).

Speaker: Shozo Yamada (The University of Tokyo)

Day_5_Yamada.mp4

QTHG2026 - Shozo Yamada.pdf

Closing

Convener: Taishi Kawamoto (Yukawa Institute for Theoretical Physics (Kyoto University from next Aprile))