The onset of spontaneous scalarization in generalised scalar-tensor theories

TL;DR

This paper investigates the conditions under which spontaneous scalarization occurs in generalized scalar-tensor theories, identifying the key factors and thresholds that trigger the transition from general relativity-like behavior to scalarized states.

Contribution

It identifies the complete set of terms controlling the onset of scalarization and determines the thresholds in generalized scalar-tensor theories based on coupling constants and object properties.

Findings

Thresholds for scalarization depend on specific coupling constants.

Scalarization occurs when compactness or curvature exceeds certain values.

The study clarifies the linear perturbation conditions for scalarization onset.

Abstract

In gravity theories that exhibit spontaneous scalarization, astrophysical objects are identical to their general relativistic counterpart until they reach a certain threshold in compactness or curvature. Beyond this threshold, they acquire a non-trivial scalar configuration, which also affects their structure. The onset of scalarization is controlled only by terms that contribute to linear perturbation around solutions of general relativity. The complete set of these terms has been identified for generalized scalar-tensor theories. Stepping on this result, we study the onset on scalarization in generalized scalar-tensor theories and determine the relevant thresholds in terms of the contributing coupling constants and the properties of the compact object.