Failure of the fluctuation-dissipation relation to ensure equilibrium

Abstract

Fluctuation-dissipation relation ensures thermodynamic equilibrium of a particle immersed in a heat bath. We will show that, under certain circumstances, the fluctuation-dissipation relation fails to ensure equilibrium between the immersed system and the heat bath. We consider a symmetry broken dimer, constrained to move in one dimension, is in compliance with the requirements of fluctuation-dissipation relation. An exact analytic result shows a nonzero average velocity of the center of mass of the dimer indicating that the state of the system is a nonequilibrium one. Based on this new physical observation, we propose an alternative paradigm for a Brownian motor which would extract useful energy directly from the heat bath unlike the ones based on Brownian Ratchet principle.