Abstracts

Invited Lectures

• Abhishek Dhar (International Centre for Theoretical Sciences, TIFR): "Fluctuating hydrodynamics of one dimensional lattice models"
  The lectures will provide an introduction to the theory of nonlinear fluctuating hydrodynamics for one dimensional models of interacting particles. Applications of the theory to systems of coupled anharmonic oscillators and spin chains will be discussed.
• Luca Delacrétaz (The University of Chicago): "Effective Field Theories for Thermalizing Systems: Structure and Applications"
  Effective field theories (EFTs) offer a powerful framework to understand collective effects in many-body systems. I will present an EFT approach for thermalization and hydrodynamics, which systematically captures the late time dynamics of thermalizing systems. We will see how to identify the strong coupling scale of hydrodynamics, learn how the EFT can make controlled predictions below this scale in an expansion in loops (or hydrodynamic fluctuations), and finally study some of its surprising predictions including "diffuson cascades".
• Tomohiro Tanogami (Osaka University): "Thermal noise effects on turbulence"
  In this lecture, we review the effects of thermal noise on fully developed fluid turbulence from the perspective of Onsager’s “ideal turbulence” theory and information thermodynamics. First, we briefly review the basic experimental observations and phenomenology of turbulence. We then give a brief overview of Onsager’s theory and discuss its implications for the intrinsic unpredictability caused by thermal noise. Finally, we discuss our recent findings on scale-to-scale information flow in turbulence.
• Taiki Haga (Osaka Metropolitan University): "Introduction to functional renormalization group"
  The functional renormalization group (FRG) is an extension of the renormalization group techniques, designed to handle systems where the interactions are complex and strongly coupled. It provides a framework to study the evolution of entire correlation functions as an infrared cutoff scale varies. In this lecture, I will present the basic principles of FRG and its mathematical formulation, using the Ising model as a prototypical example.

Invited Talks

• Yukinao Akamatsu (Yukinao Akamatsu): "Hydrodynamic fluctuations and its kinetic descriptions"
  I review recent progress in hydrodynamic fluctuations in the context of relativistic heavy-ion collisions. Characteristic of this system is the expanding background flow, which enables us to separate the short wavelength fluctuations and the long wavelength background. I will explain how an effective kinetic description for the fluctuations on 1+1 dimensional expansion reproduces renormalization of pressure and viscous coefficients, and how it yields a new contribution associated with the long-time tail phenomena. Finally, if time allows, I will briefly talk about hydrodynamic fluctuations on general backgrounds.
• Keisuke Fujii (The University of Tokyo): "Hydrodynamics in strongly correlated quantum gases"
  Thanks to their high experimental controllability, ultracold atomic systems offer an ideal platform for investigating quantum many-body systems. In particular, the tunability of interaction strength enables us to study collective phenomena due to interactions in quantum gases, especially their hydrodynamic behavior, in a well-controlled manner.In this talk, I will briefly review the hydrodynamic behavior of strongly correlated quantum gases realized in ultracold atoms and discuss studies on hydrodynamic phenomena utilizing the experimental controllability of the systems.
• Harukuni Ikeda (Gakushuin University): "Minimum scaling model and exact exponents for the Nambu-Goldstone modes in the Vicsek Model"
  We investigate the scaling behavior of Nambu-Goldstone (NG) modes in the ordered phase of the Vicsek model, introducing a phenomenological equation of motion (EOM) incorporating a previously overlooked non-linear term. This term arises from the interaction between velocity fields and density fluctuations, leading to new scaling behaviors. We derive exact scaling exponents in two dimensions, which reproduce the isotropic scaling behavior reported in a prior numerical simulation.
• Yuki Minami (Gifu University): "Anomalous Heat Conduction in Anharmonic Chains with Space Reversal Symmetry"
  Molecular dynamics simulations reveal a non-trivial scaling exponent for the anomalous heat conduction in anharmonic chains with space reversal symmetry. However, a mode coupling theory predicts a trivial scaling exponent, and no theoretical framework currently accounts for the observed non-trivial exponent. To address this discrepancy, we investigate the anomalous heat conduction in anharmonic chains with space reversal symmetry using the renormalization group. Our findings indicate that nonlinear fluctuating hydrodynamics for the anharmonic chain possesses a non-trivial fixed point and scaling exponents. In addition, we perform numerical simulations of the fluctuating hydrodynamics, demonstrating that the naive scenario in the mode coupling theory fails and that nonlinear interactions are significant.
• Hiroyoshi Nakano (ISSP, The University of Tokyo): "Operational Estimation Method for Bare Viscosity in Fluctuating Hydrodynamics: Role of Ultraviolet Cutoff"
  Fluctuating hydrodynamics is an extension of deterministic hydrodynamics, used to describe macroscopic fluctuations arising from the thermal motion of molecules. This framework has been widely applied to study the fundamental nature of nonequilibrium fluctuations. In our study, we examine the basic properties of bare viscosity—a key parameter in fluctuating hydrodynamics. Since the 1970s, it has been recognized that the bare viscosity differs from the viscosity used in deterministic hydrodynamics. In particular, in low-dimensional fluids, the difference between the two viscosities is significant: the viscosity in deterministic hydrodynamics diverges with system size, whereas the bare viscosity remains independent of system size. However, until now, there has been no established method for determining the value of the bare viscosity. This limitation has significantly constrained the quantitative application of fluctuating hydrodynamics. Indeed, the fundamental issue of how accurately fluctuating hydrodynamics can describe natural phenomena remains unclear. Given these circumstances, we focus on two-dimensional fluids and propose an operational method for estimating the bare viscosity by examining fluid behaviors near solid walls. Our study consists of four parts:
  1. Review of the ultraviolet cutoff dependence of fluctuating hydrodynamics.
  2. Proposition of an operational estimation method for the bare viscosity.
  3. Numerical demonstration of the interdependence between the bare viscosity and the ultraviolet cutoff.
  4. Numerical demonstration of the predictive ability of fluctuating hydrodynamics at the atomic scale.
• Yusuke Nishida (Tokyo Institute of Technology): "Nonrelativistic conformality, contact correlation, and duality in one dimension"
  I will discuss some aspects of the bulk viscosity in nonrelativistic quantum gases, such as nonrelativistic conformal invariance and its implication for the hydrodynamics, Kubo formula for the bulk viscosity and contact correlation function, and Bose-Fermi duality in one dimension interchanging weak and strong couplings.
• Makiko Sasada (The University of Tokyo): "Macroscopic scaling limits of the box ball system"
  The box-ball system (BBS) is a one-dimensional cellular automaton introduced by Takahashi and Satsuma, which exhibits solitonic behaviour, and is known as a discrete counterpart of the KdV equation. We deduce a generalized hydrodynamic limit for the BBS, which explains how the densities of solitons of different sizes evolve macroscopically under Euler space-time scaling. For smooth initial conditions, we further show that the resulting evolution of the soliton densities in space can be characterized by a partial differential equation, which naturally links the time-derivatives of the soliton densities and the ‘effective speeds’ of solitons locally. The equation is consistent with the so-called generalized hydrodynamic equation. We also study the space-time scaling limits of tagged solitons under shift-ergodic invariant distributions. In particular, we prove the large deviation principle in Euler space-time scaling and the invariance principle in diffusive space-time scaling under the Bernoulli product measures and Markov measures. The first part of the talk is based on a joint work with David Croydon, and the second part is based on a joint work in progress with Stefano Olla and Hayate Suda.

Topic Contributions

• Masaru Hongo (Niigata University): "Fluctuating hydrodynamics and renormalization"
• Ryo Araki (Tokyo University of Science): "Information Perspectives on Turbulent Cascade"
• Ken Hiura (The University of Tokyo): "Thermal Transport in 2D Rotor Model"
• Hisao Hayakawa (YITP, Kyoto University): "Quantum Mpemba effect"
• Yuta Kuroda (Nagoya University): "Hyperuniformity in chiral active fluids"
• Masataka Watanabe (Nagoya University): "A unified look at Asymmetric Simple Exclusion Processes and their variants"
• Yutaro Kado (Kyoto University): "Microscopic cut-off dependence of an entropic force in interface propagation of stochastic order parameter dynamics"
• Hiromu Ushihara (The University of Tokyo): "Quantum master equations and tensor networks toward thermal transport"
• Hideaki Nishikawa (Kyoto University): "Anomalous Diffusion and Fluctuating Hydrodynamics in Long-range Interacting Systems"