The phase transition of the diffusive pair contact process revisited

TL;DR

This paper revisits the critical behavior of the diffusive pair contact process, challenging recent claims of a new universality class, and suggests it may instead belong to the well-known directed percolation class.

Contribution

The study provides evidence that the critical behavior of the PCPD may not be a new universality class but aligns with directed percolation, contrary to recent proposals.

Findings

Effective exponents exhibit slow drift over time.

Numerical results are consistent with directed percolation.

The asymptotic critical behavior may be governed by a DP fixed point.

Abstract

The restricted diffusive pair contact process 2A->3A, 2A->0 (PCPD) and the classification of its critical behavior continues to be a challenging open problem of non-equilibrium statistical mechanics. Recently Kockelkoren and Chate [Phys. Rev. Lett. 90, 125701 (2003)] suggested that the PCPD in one spatial dimension represents a genuine universality class of non-equilibrium phase transitions which differs from previously known classes. To this end they introduced an efficient lattice model in which the number of particles per site is unrestricted. In numerical simulations this model displayed clean power laws, indicating ordinary critical behavior associated with certain non-trivial critical exponents. In the present work, however, we arrive at a different conclusion. Increasing the numerical effort, we find a slow drift of the effective exponents which is of the same type as observed in previously studied fermionic realizations. Analyzing this drift we discuss the possibility that the asymptotic critical behavior of the PCPD may be governed by an ordinary directed percolation fixed point.