Thermodynamic variational relation

Abstract: In systems far from equilibrium, the statistics of observables are connected to entropy production, leading to the Thermodynamic Uncertainty Relation (TUR). However, the derivation of TURs often involves constraining the parity of observables, such as considering asymmetric currents, making it unsuitable for the general case. We propose a Thermodynamic Variational Relation (TVR) between the statistics of general observables and entropy production, based on the variational representation of $f$-divergences. From this result, we derive a universal TUR and other relations for higher-order statistics of observables.