Nonequilibrium steady state fluctuations in actively cooled resonators

TL;DR

This paper investigates heat and work fluctuations in a feedback-cooled resonator, demonstrating how nonequilibrium steady states can be characterized through fluctuation asymmetries, with experimental results aligning with theoretical Langevin models.

Contribution

It provides a detailed analysis of nonequilibrium fluctuations in a macroscopic resonator cooled by active feedback, linking experimental data with stochastic theoretical models.

Findings

Fluctuations agree with Langevin system predictions

Asymmetry in heat fluctuations indicates nonequilibrium state

Feedback cooling causes measurable departure from equilibrium

Abstract

We analyze heat and work fluctuations in the gravitational wave detector AURIGA, modeled as a macroscopic electromechanical oscillator in contact with a thermostat and cooled by an active feedback system. The oscillator is driven to a steady state by the feedback cooling, equivalent to a viscous force. The experimentally measured fluctuations are in agreement with our theoretical analysis based on a stochastically driven Langevin system. The asymmetry of the fluctuations of the absorbed heat characterizes the oscillator's nonequilibrium steady state and reveals the extent to which a feedback cooled system departs from equilibrium in a statistical mechanics perspective.