Horndeski theories self-tuning to a de Sitter vacuum

Abstract

We consider Horndeski cosmological models able to screen the vacuum energy coming from any field theory assuming that after this screening the space should be in a de Sitter vacuum with a particular value of the cosmological constant specified by the theory of gravity itself. The most general scalar-tensor cosmological models without higher than second order derivatives in the field equations that have a spatially flat de Sitter critical point for any kind of material content or vacuum energy are, therefore, presented. These models could allow us to understand the current accelerated expansion of the universe as the result of a dynamical evolution towards a de Sitter attractor.

V1: 5 pages. V2: 8 pages; 5 references added; 2 new appendixes; clarifications in the discussion; no physics changes. This version accepted for publication in Physical Review D