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.
Highlights
Introduction and SummaryThe detections of gravitational waves produced in mergers of compact objects [1, 2] have revolutionised the field of gravitational physics, giving rise to the era of gravitational wave astronomy
In this paper we consider gravitational collapse in Horndeski theories using as initial data a spherically symmetric lump of scalar field (2.5)
Even though the initial data is spherically symmetric, we evolve it using a 3+1 evolution code based on GRChombo [44], without symmetry assumptions
Summary
The detections of gravitational waves produced in mergers of compact objects [1, 2] have revolutionised the field of gravitational physics, giving rise to the era of gravitational wave astronomy. One particular modified theory of gravity which is known to have a well-posed initial value problem is Horndeski theory [17,18,19].2 This is the most general theory of a metric tensor coupled to a scalar field with second order equations of motion arising from a diffeomorphism invariant action in four spacetime dimensions.. Our goal is to identify the region in the space of couplings for which the Horndeski theories under consideration are weakly coupled throughout the evolution Using these results, in a companion paper we study black hole binary mergers, treating the theory fully non-linearly while remaining the regime of validity of EFT in all phases of the binary. We summarise the main results in the present article, and refer the reader to the companion paper [43] for the results on black hole binaries
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