Universality-class crossover by a nonorder field introduced to the pair contact process with diffusion

Area of Science:

• Statistical Mechanics
• Complex Systems
• Phase Transitions

Background:

• The universality class of the one-dimensional pair contact process with diffusion (PCPD) remains debated.
• Previous arguments suggested PCPD shares critical behavior with models in the directed percolation (DP) universality class.

Purpose of the Study:

• To investigate the critical behavior of the PCPD and its relation to the DP universality class.
• To determine if diffusing particles in PCPD exhibit the same critical phenomena as frozen particles.

Main Methods:

• Numerical simulation of a modified PCPD model.
• Introduction of a nonorder field associated with infinitely many absorbing states.
• Analysis of crossover phenomena and comparison with similar models.

Main Results:

• A crossover from PCPD to DP universality was observed upon introducing a nonorder field.
• The introduction of a nonorder field alone does not typically induce crossovers between models in the same universality class.
• The observed crossover is attributed to fundamental differences between the PCPD and DP universality classes.

Conclusions:

• The PCPD does not belong to the directed percolation universality class.
• Diffusing particles in PCPD do not behave identically to frozen particles concerning critical behavior.
• The study clarifies the distinct universality class of the PCPD through numerical investigation.