Observational constraints on late-time Lambda(t) cosmology

TL;DR

This paper investigates a cosmological model with a decaying vacuum energy density proportional to the Hubble parameter, testing its viability against recent observational data to distinguish it from the standard Lambda Cold Dark Matter model.

Contribution

It introduces and tests a late-time Lambda(t) cosmology with a vacuum energy decaying linearly with the Hubble parameter using multiple observational datasets.

Findings

The model is consistent with current observational data.

It provides a potential alternative to the standard cosmological constant scenario.

The approach offers a way to address the cosmological constant problem.

Abstract

The cosmological constant, i.e., the energy density stored in the true vacuum state of all existing fields in the Universe, is the simplest and the most natural possibility to describe the current cosmic acceleration. However, despite its observational successes, such a possibility exacerbates the well known cosmological constant problem, requiring a natural explanation for its small, but nonzero, value. In this paper we study cosmological consequences of a scenario driven by a varying cosmological term, in which the vacuum energy density decays linearly with the Hubble parameter. We test the viability of this scenario and study a possible way to distinguish it from the current standard cosmological model by using recent observations of type Ia supernova (Supernova Legacy Survey Collaboration), measurements of the baryonic acoustic oscillation from the Sloan Digital Sky Survey and the position of the first peak of the cosmic microwave background angular spectrum from the three-year Wilkinson Microwave Anisotropy Probe.