Consequences of Fine-Tuning for Fifth Force Searches

TL;DR

This paper investigates how self-interactions in light bosonic fields affect constraints on fifth forces, revealing that natural interactions can both enhance detection prospects and impose new limits through vacuum stability considerations.

Contribution

It introduces the impact of natural self-interactions on fifth force constraints, highlighting new experimental and theoretical bounds, including effects on equivalence principle tests and vacuum decay.

Findings

Self-interactions can turn EP-preserving forces into EP-violating ones.

Stellar systems like PSR J0337+1715 provide strong constraints on fifth forces.

Self-interactions influence vacuum stability, leading to new decay constraints.

Abstract

Light bosonic fields mediate long range forces between objects. If these fields have self-interactions, i.e., non-quadratic terms in the potential, the experimental constraints on such forces can be drastically altered due to a screening (chameleon) or enhancement effect. We explore how technically natural values for such self-interaction coupling constants modify the existing constraints. We point out that assuming the existence of these natural interactions leads to new constraints, contrary to the usual expectation that screening leads to gaps in coverage. We discuss how screening can turn fundamentally equivalence principle (EP)-preserving forces into EP-violating ones. This means that when natural screening is present, searches for EP violation can be used to constrain EP-preserving forces. We show how this effect enables the recently discovered stellar triple system \textit{PSR J0337$+$1715} to place a powerful constraint on EP-preserving fifth forces. Finally, we demonstrate that technically natural cubic self-interactions modify the vacuum structure of the scalar potential, leading to new constraints from spontaneous and induced vacuum decay.