Nonequilibrium fluctuation-response relations for state-current correlations

Area of Science:

• Statistical Mechanics
• Non-equilibrium Thermodynamics
• Physical Chemistry

Background:

• Exact fluctuation-response relations (FRRs) have been established for nonequilibrium steady states of Markov jump processes.
• These FRRs connect fluctuations of observables to their responses to perturbations in transition rates.

Purpose of the Study:

• To derive FRRs for mixed covariances involving one state and one current observable.
• To develop inverse FRRs that express individual responses using covariances.
• To investigate the conditions for Onsager symmetry breaking.

Main Methods:

• Derivation of generalized fluctuation-response relations for Markov jump processes.
• Analysis of mixed state-current covariances.
• Application of derived relations to understand Onsager symmetry.

Main Results:

• Analogous FRRs derived for mixed covariances of state and current observables.
• Inverse FRRs developed, expressing responses in terms of covariances.
• Demonstrated that state-current correlations are necessary for breaking Onsager symmetry.

Conclusions:

• The study extends FRRs to mixed state-current observables, providing deeper insights into non-equilibrium systems.
• The findings offer practical applications in understanding fluctuations in quantum dot devices and enzymatic reaction networks.