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DY: Fachverband Dynamik und Statistische Physik

DY 32: Nonlinear Stochastic Systems

DY 32.1: Hauptvortrag

Donnerstag, 20. März 2025, 09:30–10:00, H43

Fluctuation-Response Relations for Non-equilibrium Systems — •Benjamin Lindner — Institut für Physik, Humboldt-Universität Berlin

The fluctuations and the response of stochastic systems are related by fluctuation-dissipation theorems or, equivalently, fluctuation-response relations (FRRs). Originally introduced for systems in thermodynamic equilibrium, generalizations of such relations for non-equilibrium situations have been discussed since the 1970's and are particularly appealing for biological systems. FRRs may be used to e.g. (i) prove that a system is outside of equilibrium, (ii) prove that it does not follow Markovian dynamics, (iii) extract statistics of intrinsic noise sources. In my talk I report several FRRs in systems far from equilibrium. I discuss a nonlinear FRR for systems that can be perturbed by a step stimulus, which can be used as an efficient test of Markovianity. I present a universal description for stochastic oscillators, that results in a simple FRR in terms of a new complex-valued transform of the original oscillator variables. Last but not least, I derive a new class of FRRs for spiking neurons that relate the pronounced fluctuations of spontaneous neural firing to their average response to sensory stimuli, i.e. to the processing of sensory information that is the raison d'etre of neural systems.

Refs.: B. Lindner 129, 198101 Phys. Rev. Lett. (2022); A. Perez-Cervera et al. PNAS 120, e2303222120 (2023); K. Engbring et al. Phys. Rev. X 13, 021034(2023); J. Stubenrauch & B. Lindner Phys. Rev. X 14, 041047 (2024)

Keywords: Fluctuation-dissipation theorem; Stochastic systems and stochastic oscillators; Linear-response theory; Neural information transmission; Neural noise