My latest preprint develops a parallel between equilibrium and equiaccessible steady states, culminating in a McLennan formula for the latter.

Abstract §

Near equilibrium, the Boltzmann distribution is corrected by the transient irreversible entropy flux, a result known as the McLennan formula. By expanding around equiaccessible steady states instead, we derive an analogue that can hold arbitrarily far from equilibrium. At zeroth order, steady-state occupation is determined solely by local escape rates, yielding a strong form of the active-matter principle of “low rattling.” The first-order correction measures the impact of traffic imbalances on the accessibility of each state, marking the onset of nonlocal determinants of relative occupation.