Fluctuation Theorems for an Asymmetric Rotor in a Granular Gas

We investigate the validity of fluctuation theorems for an asymmetric rotor experiment in a granular gas. A first state, with a Gaussian distribution of the angular velocity, is found to be well described by a first order Langevin equation. We show that fluctuation theorems are valid for the injected work and for the total entropy production. In a second state, the angular velocity distribution is double peaked due to a spontaneous symmetry breaking: A convection roll develops in the granular gas, which strongly couples to the rotor. Surprisingly, in this case, similar symmetry relations hold, which lead to a good prediction for the height ratio of the two peaks.