Gravitational Collapse in Cubic Horndeski Theories

TL;DR

This paper investigates gravitational collapse within cubic Horndeski theories, analyzing conditions for global solutions, effective field theory validity, and employing numerical evolution techniques beyond spherical symmetry.

Contribution

It provides a detailed analysis of collapse dynamics in cubic Horndeski theories, including the parameter space for solutions and the regime of effective field theory validity.

Findings

Identified parameter regions allowing global solutions.

Determined the sub-region where effective field theory remains valid.

Used CCZ4 formulation for numerical evolution beyond spherical symmetry.

Abstract

We study spherically symmetric gravitational collapse in cubic Horndeski theories of gravity. By varying the coupling constants and the initial amplitude of the scalar field, we determine the region in the space of couplings and amplitudes for which it is possible to construct global solutions to the Horndeski theories. Furthermore, we identify the regime of validity of effective field theory as the sub-region for which a certain weak field condition remains small at all times. We evolve the initial data using the CCZ4 formulation of the Einstein equations and horizon penetrating coordinates without assuming spherical symmetry.