Perturbations in the relaxation mechanism for a large cosmological constant

TL;DR

This paper analyzes perturbations in a relaxation mechanism for a large cosmological constant, showing that their evolution closely resembles the standard LCDM model, especially during the matter era.

Contribution

It provides an analytical study of perturbations in a relaxation model for the cosmological constant within the LXCDM framework, highlighting similarities to LCDM.

Findings

Perturbation evolution in the relaxation model is similar to LCDM.

The model exhibits tracking properties of vacuum energy.

Cosmological background evolution matches LCDM with fine-tuned CC.

Abstract

Recently, a mechanism for relaxing a large cosmological constant (CC) has been proposed [arxiv:0902.2215], which permits solutions with low Hubble rates at late times without fine-tuning. The setup is implemented in the LXCDM framework, and we found a reasonable cosmological background evolution similar to the LCDM model with a fine-tuned CC. In this work we analyse analytically the perturbations in this relaxation model, and we show that their evolution is also similar to the LCDM model, especially in the matter era. Some tracking properties of the vacuum energy are discussed, too.