Speaker
Description
Understanding the relationship between fluctuations and response is a central problem in nonequilibrium statistical physics. While the fluctuation-dissipation theorem provides this connection near equilibrium, a general framework valid far from equilibrium remains incomplete. In this talk, I present a unified fluctuation-response framework for nonequilibrium Markovian dynamics. For discrete-state systems described by Markov jump processes, we derive fluctuation-response identities and inequalities that relate fluctuations of general observables to their responses to perturbations of transition rates. Extending these ideas to continuous-state systems, we establish a fluctuation-response theory for Langevin dynamics that connects global fluctuations of observables to their responses to perturbations in force, mobility, and temperature. Together, these results reveal a unified hierarchical structure linking various identities and inequalities, in particular clarifying the relationship between the fluctuation-dissipation theorem and thermodynamic uncertainty relations.
References
[1] E. Kwon, H.-M. Chun, H. Park, and J. S. Lee, Phys. Rev. Lett 135, 097101 (2025).
[2] H.-M. Chun, E. Kwon, H. Park, and J. S. Lee, preprint arXiv:2601.16387.