Impact of chaos and Brownian diffusion on irreversibility in Stokes flows.

We study a reversal process in Stokes flows in the presence of weak diffusion in order to clarify the distinct effects that chaotic flows have on the loss of reversibility relative to nonchaotic flows. In all linear flows, including a representation of the baker's map, we show that the decay of reversibility presents universal properties. In nonlinear chaotic and nonchaotic flows, we show that this universality breaks down due to the distribution of strain rates. In the limit of infinitesimal diffusivity, we predict qualitatively distinct behavior in the chaotic case.