Speaker
Description
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).