Rotational diffusion under torque: Microscopic reversibility and excess   entropy
  We consider rotational diffusion for two systems - a macrospin under external magnetic field, and a particle diffusing on the surface of a sphere under external torque. Microstates in the two cases transform differently under time-reversal. This results in Clausius like dependence of stochastic entropy production (EP) for macrospins, and an excess EP for diffusion of particles on sphere. The total EP in both the cases obey fluctuation theorems. For macrospins, we derive analytical expression for probability distribution of total EP in the adiabatic limit. Numerical simulations show that the distribution functions of EP agree well with theoretical predictions. 
Swarnali Bandopadhyay, Debasish Chaudhuri, and A. M. Jayannavar
cond-mat.stat-mech cond-mat.mes-hall