Experimental Measurement of the Persistence Exponent of the Planar Ising Model

Using a twisted nematic liquid crystal system exhibiting planar Ising model dynamics, we have measured the scaling exponent $\theta$ which characterizes the time evolution, $p(t) \sim t^{-\theta}$, of the probability $p(t)$ that the local order parameter has not switched its state by the time $t$. For 0.4 seconds to 200 seconds following the phase quench, the system exhibits scaling behavior and, measured over this interval, $\theta = 0.19 \pm 0.031$, in good agreement with theoretical analysis and numerical simulations.