Multi-Scaling of Correlation Functions in Single Species Reaction-Diffusion Systems

TL;DR

This paper derives multi-fractal scaling laws for particle distributions in single-species reaction-diffusion systems using renormalization group techniques, revealing exact and conjectured behaviors in different dimensions.

Contribution

It provides the first derivation of multi-fractal scaling laws for these systems and shows the absence of higher-order epsilon corrections for certain particle counts.

Findings

Derived scaling laws for binary and ternary reactions in different dimensions.

Confirmed the absence of higher-order epsilon corrections for N=1,2,3,4.

Conjectured the absence of epsilon^2 corrections for all N.

Abstract

We derive the multi-fractal scaling of probability distributions of multi-particle configurations for the binary reaction-diffusion system $A+A \to \emptyset$ in $d \leq 2$ and for the ternary system $3A \to \emptyset$ in $d=1$. For the binary reaction we find that the probability $P_{t}(N, \Delta V)$ of finding $N$ particles in a fixed volume element $\Delta V$ at time $t$ decays in the limit of large time as $(\frac{\ln t}{t})^{N}(\ln t)^{-\frac{N(N-1)}{2}}$ for $d=2$ and $t^{-Nd/2}t^{-\frac{N(N-1)\epsilon}{4}+\mathcal{O}(\ep^2)}$ for $d<2$. Here $\ep=2-d$. For the ternary reaction in one dimension we find that $P_{t}(N,\Delta V) \sim (\frac{\ln t}{t})^{N/2}(\ln t)^{-\frac{N(N-1)(N-2)}{6}}$. The principal tool of our study is the dynamical renormalization group. We compare predictions of $\ep$-expansions for $P_{t}(N,\Delta V)$ for binary reaction in one dimension against exact known results. We conclude that the $\ep$-corrections of order two and higher are absent in the above answer for $P_{t}(N, \Delta V)$ for $N=1,2,3,4$. Furthermore we conjecture the absence of $\ep^2$-corrections for all values of $N$.