Observational tests for \Lambda(t)CDM cosmology

TL;DR

This paper tests a class of cosmological models where vacuum energy decays with the Hubble parameter, comparing their fit to observational data against standard models, and finds they are similarly consistent with current measurements.

Contribution

It introduces and evaluates observational tests for mbda(t)CDM models with vacuum decay, comparing their fit to data and analyzing differences due to SNe light-curve methods.

Findings

Both models fit the data well with similar hi^2 values.

SNe light-curve fitting methods influence parameter estimation.

The matter power spectrum analysis aligns with standard constraints.

Abstract

We investigate the observational viability of a class of cosmological models in which the vacuum energy density decays linearly with the Hubble parameter, resulting in a production of cold dark matter particles at late times. Similarly to the flat \Lambda CDM case, there is only one free parameter to be adjusted by the data in this class of \Lambda(t)CDM scenarios, namely, the matter density parameter. To perform our analysis we use three of the most recent SNe Ia compilation sets (Union2, SDSS and Constitution) along with the current measurements of distance to the BAO peaks at z = 0.2 and z = 0.35 and the position of the first acoustic peak of the CMB power spectrum. We show that in terms of $\chi^2$ statistics both models provide good fits to the data and similar results. A quantitative analysis discussing the differences in parameter estimation due to SNe light-curve fitting methods (SALT2 and MLCS2k2) is studied using the current SDSS and Constitution SNe Ia compilations. A matter power spectrum analysis using the 2dFGRS is also performed, providing a very good concordance with the constraints from the SDSS and Constitution MLCS2k2 data.