Proportion of unaffected sites in a reaction-diffusion process
Proportion of unaffected sites in a reaction-diffusion process
We consider the probability $P(t)$ that a given site remains unvisited by any of a set of random walkers in $d$ dimensions undergoing the reaction $A+A\to0$ when they meet. We find that asymptotically $P(t)\sim t^{-\theta}$ with a universal exponent $\theta=\ffrac12-O(\epsilon)$ for $d=2-\epsilon$, while, for $d>2$, $\theta$ is non-universal and depends …