Product-form Poisson-like distributions and complex balanced reaction systems

TL;DR

This paper characterizes stochastically complex balanced biochemical reaction networks, linking their stationary distributions to deterministic properties, and proves a stochastic deficiency zero theorem showing product-form Poisson-like distributions arise in these systems.

Contribution

It introduces the concept of stochastically complex balanced systems, establishes their equivalence with deterministic complex balanced networks, and proves a stochastic deficiency zero theorem for reaction networks.

Findings

Stochastically complex balanced systems have product-form Poisson-like stationary distributions.

A network is stochastically complex balanced if and only if its deterministic counterpart is complex balanced.

Deficiency zero reaction networks exhibit Poisson-like stationary distributions across all irreducible components.

Abstract

Stochastic reaction networks are dynamical models of biochemical reaction systems and form a particular class of continuous-time Markov chains on $\mathbb{N}^n$. Here we provide a fundamental characterisation that connects structural properties of a network to its dynamical features. Specifically, we define the notion of `stochastically complex balanced systems' in terms of the network's stationary distribution and provide a characterisation of stochastically complex balanced systems, parallel to that established in the 70-80ies for deterministic reaction networks. Additionally, we establish that a network is stochastically complex balanced if and only if an associated deterministic network is complex balanced (in the deterministic sense), thereby proving a strong link between the theory of stochastic and deterministic networks. Further, we prove a stochastic version of the `deficiency zero theorem' and show that any (not only complex balanced) deficiency zero reaction network has a product-form Poisson-like stationary distribution on all irreducible components. Finally, we provide sufficient conditions for when a product-form Poisson-like distribution on a single (or all) component(s) implies the network is complex balanced, and explore the possibility to characterise complex balanced systems in terms of product-form Poisson-like stationary distributions.