A Compendium of Chameleon Constraints

TL;DR

This paper consolidates astrophysical and laboratory constraints on the chameleon scalar field model, a dark energy candidate, revealing remaining viable parameter space and guiding future detection efforts.

Contribution

It provides the first combined analysis of astrophysical and laboratory constraints on the chameleon model, clarifying the remaining parameter space.

Findings

Identified the remaining viable regions of chameleon parameter space.

Combined constraints from diverse astrophysical and laboratory data.

Discussed implications for future cosmological and small-scale searches.

Abstract

The chameleon model is a scalar field theory with a screening mechanism that explains how a cosmologically relevant light scalar can avoid the constraints of intra-solar-system searches for fifth-forces. The chameleon is a popular dark energy candidate and also arises in $f(R)$ theories of gravity. Whilst the chameleon is designed to avoid historical searches for fifth-forces it is not unobservable and much effort has gone into identifying the best observables and experiments to detect it. These results are not always presented for the same models or in the same language, a particular problem when comparing astrophysical and laboratory searches making it difficult to understand what regions of parameter space remain. Here we present combined constraints on the chameleon model from astrophysical and laboratory searches for the first time and identify the remaining windows of parameter space. We discuss the implications for cosmological chameleon searches and future small-scale probes.