Bulk Viscosity and Particle Creation in the Inflationary Cosmology

TL;DR

This paper investigates how bulk viscosity and particle creation influence early universe inflation, providing causal thermodynamic solutions that align with Lambda-CDM and recent observational data.

Contribution

It introduces a causal thermodynamic approach to particle creation with bulk viscosity, yielding analytical inflationary solutions free of initial singularities.

Findings

Analytical solutions match Lambda-CDM behavior

Inflation driven by bulk viscosity with particle creation

Model constrained by Planck data

Abstract

We study particle creation in the presence of bulk viscosity of cosmic fluid in the early universe within the framework of open thermodynamical systems. Since the first-order theory of non-equilibrium thermodynamics is non-causal and unstable, we try to solve the bulk viscosity equation of the cosmic fluid with particle creation through the full causal theory. By adopting an appropriate function for particle creation rate of "Creation of Cold Dark Matter" model, we obtain analytical solutions which do not suffer from the initial singularity and are in agreement with equivalent solutions of Lambda-CDM model. We constrain the free parameter of particle creation in our model based on recent Planck data. It is also found that the inflationary solution is driven by bulk viscosity with or without particle creation.