Exact Solution of Two-Species Ballistic Annihilation with General Pair-Reaction Probability

TL;DR

This paper provides an exact analytical solution for a two-species ballistic annihilation model with a general pair-reaction probability less than one, incorporating stochastic fluctuations in reaction and particle currents.

Contribution

It extends previous models by including probabilistic reactions and fluctuations, offering a comprehensive exact solution for the stochastic dynamics of ballistic annihilation.

Findings

Exact solution for reaction zone dynamics

Comparison of intrinsic and extrinsic fluctuation effects

Insights into stochastic behavior with non-unity reaction probability

Abstract

The reaction process $A+B->C$ is modelled for ballistic reactants on an infinite line with particle velocities $v_A=c$ and $v_B=-c$ and initially segregated conditions, i.e. all A particles to the left and all B particles to the right of the origin. Previous, models of ballistic annihilation have particles that always react on contact, i.e. pair-reaction probability $p=1$. The evolution of such systems are wholly determined by the initial distribution of particles and therefore do not have a stochastic dynamics. However, in this paper the generalisation is made to $p<1$, allowing particles to pass through each other without necessarily reacting. In this way, the A and B particle domains overlap to form a fluctuating, finite-sized reaction zone where the product C is created. Fluctuations are also included in the currents of A and B particles entering the overlap region, thereby inducing a stochastic motion of the reaction zone as a whole. These two types of fluctuations, in the reactions and particle currents, are characterised by the `intrinsic reaction rate', seen in a single system, and the `extrinsic reaction rate', seen in an average over many systems. The intrinsic and extrinsic behaviours are examined and compared to the case of isotropically diffusing reactants.