Accelerating Horndeski cosmologies screening the vacuum energy

TL;DR

This paper develops the most general second-order scalar-tensor cosmological models within Horndeski theories that can dynamically screen vacuum energy, leading to a stable de Sitter universe consistent with accelerated expansion.

Contribution

It introduces a comprehensive class of Horndeski models capable of screening vacuum energy and achieving a stable de Sitter phase regardless of matter content.

Findings

Models allow for a fixed de Sitter critical point for any vacuum energy.

The universe's accelerated expansion can be explained as evolution towards an attractor.

Provides a framework for understanding dark energy within Horndeski theories.

Abstract

In the context of Horndeski cosmologies, we consider a dynamical adjustment mechanism able to screen any value of the vacuum energy of the matter fields leading to a fixed de Sitter geometry. Thus, we present the most general scalar-tensor cosmological models without higher than second order derivatives in the field equation that have a fixed spatially flat de Sitter critical point for any kind of material content or vacuum energy. These models allow us to understand the current accelerated expansion of the universe as the result of the evolution towards the critical point when it is an attractor.