Non-reciprocity drives a Brownian dimer out of equilibrium
arXiv:2607.27740
The paper analyzes a minimal two‑dimensional Brownian dimer whose two particles are coupled by a non‑reciprocal harmonic spring, showing that this non‑reciprocity alone can drive the system out of equilibrium and providing exact steady‑state distributions and currents for the zero‑rest‑length case and numerical results for finite rest length.
Abstract
We consider the minimal model of a two dimensional Brownian dimer consisting of two overdamped monomers, trapped in an isotropic harmonic potential and mutually coupled by a non-reciprocal harmonic spring that violates Newton's action-reaction principle. We have shown that the non-reciprocal interaction alone can drive the system far from equilibrium, in the absence of any external time dependent drive and being in contact with a single thermal bath. The exact steady state probability distribution and current are explicitly calculated for the zero-rest-length limit of the spring, which eventually maps our model to another non-equilibrium phenomenon, called Brownian gyration. For a spring with finite rest length, these quantities are calculated numerically.