Single field matter bounce with dark energy era: comparison with CMB Planck 2018 data and best fit parameters

TL;DR

This study uses Planck 2018 CMB data to evaluate a matter bounce cosmological model with a scalar field, finding it comparable to the standard inflationary Lambda-CDM model in fitting observations.

Contribution

The paper performs MCMC analyses on a matter bounce model with a scalar field and compares its fit to Planck data against the standard Lambda-CDM model, highlighting its viability.

Findings

Planck data alone cannot distinguish between the matter bounce model and Lambda-CDM.

The matter bounce model can produce a scalar spectral index compatible with observations.

The model's parameters are constrained by the data, showing its potential as an alternative cosmology.

Abstract

In this work, we perform Markov Chain Monte Carlo (MCMC) analyses using the Planck 2018 cosmic microwave background (CMB) datasets, including temperature, polarization, and lensing, in order to compare matter bounce models with observational data. The particular model we considered contains a scalar field with an exponential potential, which behaves as dust in the asymptotic past of the contracting phase, it realizes a quantum bounce, and then behaves as a transient dark energy field at large scales in the expanding phase. The parameter $\lambda$ appearing in the exponential potential is directly related to the model's scalar spectral index, $n_s$, which is set free in the MCMC analyses, as well as the deepness of the bounce, which controls the amplitude of the power spectrum. We provide constraints on the cosmological parameters and compare the model's performance against the standard inflationary $\Lambda$CDM scenario. Our results indicate that Planck data alone cannot favor one model with respect to the other, showing that the model we investigate can be a viable alternative to inflation.