Generalised scalar-tensor theories and self-tuning

TL;DR

This paper investigates a class of generalized scalar-tensor theories that can self-tune to low-scale anti de Sitter vacua, potentially addressing the cosmological constant problem while remaining compatible with solar system tests.

Contribution

It introduces a novel family of scalar-tensor theories that achieve self-tuning through a subtle balance of scalar coupling and mass, avoiding reliance on non-linear screening mechanisms.

Findings

Self-tuning solutions exist in the proposed theories.

Compatibility with solar system tests is demonstrated.

Theories suggest a link between early universe inflation and vacuum energy cancellation.

Abstract

We explore a family of generalised scalar-tensor theories that exhibit self-tuning to low scale anti de Sitter vacua, even in the presence of a large cosmological constant. We are able to examine the linearised fluctuations about these vacua and compute the corresponding amplitude. Thanks to a subtle interplay between a weak scalar coupling and a low scalar mass, it is possible to exhibit self-tuning and compatibility with solar system tests of gravity without resorting to non-linearities and unreliable screening mechanisms. The weakness of the scalar coupling and the correspondingly slow response to vacuum energy phase transitions may present some interesting possibilities for connecting early universe inflation to the cancellation of vacuum energy.