FRW Cosmologies with Adiabatic Matter Creation

TL;DR

This paper explores cosmological models with adiabatic matter creation in FRW universes, deriving key relations, discussing inflation conditions, and proposing a modified hot big-bang model consistent with observations.

Contribution

It introduces a simple relation between particle number density and energy density for matter creation models and proposes a minimally modified hot big-bang scenario with observationally consistent ages.

Findings

Derived a universal relation between n and ρ for adiabatic matter creation.

Identified conditions under which inflation can occur in these models.

Showed that the models can produce ages compatible with observations despite high Hubble rates.

Abstract

Some properties of cosmological models with matter creation are investigated in the framework of the Friedman-Robertson-Walker (FRW) line element. For adiabatic matter creation, as developed by Prigogine and coworkers, we derive a simple expression relating the particle number density $n$ and energy density $\rho$ which holds regardless of the matter creation rate. The conditions to generate inflation are discussed and by considering the natural phenomenological matter creation rate $\psi =3 \beta nH$, where $\beta$ is a pure number of the order of unity and $H$ is the Hubble parameter, a minimally modified hot big-bang model is proposed. The dynamic properties of such models can be deduced from the standard ones simply by replacing the adiabatic index $\gamma$ of the equation of state by an effective parameter $\gamma_{*} = \gamma (1 - \beta)$. The thermodynamic behavior is determined and it is also shown that ages large enough to agree with observations are obtained even given the high values of $H$ suggested by recent measurements.