Persistence exponents in a three-dimensional symmetric binary fluid mixture

The persistence exponent, θ, is defined by N_F~t^-θ, where t is the time since the start of the coarsening process and the ``no-flip fraction,'' N<sub>F</sub>, is the number of points that have not seen a change of ``color'' since t=0. Here we investigate numerically the persistence exponent for a binary fluid system where the coarsening is dominated by hydrodynamic transport. We find that N_F follows a power law decay (as opposed to exponential) with the value of θ somewhat dependent on the domain growth rate (L~t^α, where L is the average domain size), in the range θ=1.23+/-0.1 (α=2/3) to θ=1.37+/-0.2 (α=1). These α values correspond to the inertial and viscous hydrodynamic regimes, respectively.