An Accelerating Cosmology Without Dark Energy

TL;DR

This paper examines a cosmological model where particle creation drives acceleration without dark energy, testing its consistency with high-redshift CMB data and low-redshift supernova observations, revealing tensions between these constraints.

Contribution

It extends previous models by including baryons and radiation, and tests their viability against multiple cosmological constraints, highlighting challenges in reconciling data.

Findings

Tension between high-redshift CMB and low-redshift supernova data.

Inclusion of baryons and radiation affects model viability.

Model struggles to fit both early and late universe observations.

Abstract

The negative pressure accompanying gravitationally-induced particle creation can lead to a cold dark matter (CDM) dominated, accelerating Universe (Lima et al. 1996) without requiring the presence of dark energy or a cosmological constant. In a recent study Lima et al. (2008, LSS) demonstrated that particle creation driven cosmological models are capable of accounting for the SNIa observations of the recent transition from a decelerating to an accelerating Universe. Here we test the evolution of such models at high redshift using the constraint on z_eq, the redshift of the epoch of matter radiation equality, provided by the WMAP constraints on the early Integrated Sachs-Wolfe effect. Since the contribution of baryons and radiation was ignored in the work of LSS, we include them in our study of this class of models. The parameters of these more realistic models with continuous creation of CDM is tested and constrained at widely-separated epochs (z = z_eq and z = 0) in the evolution of the Universe. This comparison reveals a tension between the high redshift CMB constraint on z_eq and that which follows from the low redshift SNIa data, challenging the viability of this class of models.