Cosmological consequences of an adiabatic matter creation process

TL;DR

This paper explores how continuous matter creation affects cosmology, analyzing models' impacts on the CMB spectrum, introducing a model-independent diagnostic, and testing thermodynamic laws within this framework.

Contribution

It presents three phenomenological models of adiabatic matter creation, introduces an $Om$ diagnostic to distinguish models from $ ext{Lambda}$CDM, and examines thermodynamic laws in this context.

Findings

Particle production rate is inversely proportional to $Om$.

The $Om$ diagnostic can differentiate cosmological models without precise matter density.

The generalized second law of thermodynamics holds at the apparent horizon.

Abstract

In this paper we investigate the cosmological consequences of a continuous matter creation associated with the production of particles by the gravitational field acting on the quantum vacuum. To illustrate this, three phenomenological models are considered. An equivalent scalar field description is presented for each models. The effects on the cosmic microwave background power spectrum are analyzed for the first time in the context of adiabatic matter creation cosmology. Further, we introduce a model independent treatment, $Om$, which depends only on the Hubble expansion rate and the cosmological redshift to distinguish any cosmological model from $\Lambda$CDM by providing a null test for the cosmological constant, meaning that, for any two redshifts $z_1$, $z_2$, $Om (z)$ is same, i.e. $Om (z_1)- Om (z_2)= 0$. Also, this diagnostic can differentiate between several cosmological models by indicating their quintessential/ phantom behavior without knowing the accurate value of the matter density, and the present value of the Hubble parameter. For our models, we find that particle production rate is inversely proportional to $Om$. Finally, the validity of the generalized second law of thermodynamics bounded by the apparent horizon has been examined.