Stellar Pulsations in Beyond Horndeski Gravity Theories

TL;DR

This paper investigates how beyond Horndeski gravity theories affect stellar pulsations, proposing that certain stars like brown dwarfs and Cepheids could serve as tests for these alternative gravity models.

Contribution

It derives and solves the wave equation for stellar oscillations within beyond Horndeski theories, identifying promising stellar candidates for testing deviations from general relativity.

Findings

Brown dwarfs and Cepheid stars are highly sensitive to gravity modifications.

Modified pulsation periods can serve as observational tests for the theory.

Preliminary survey suggests specific stars as optimal candidates for future experiments.

Abstract

Theories of gravity in the beyond Horndeski class recover the predictions of general relativity in the solar system whilst admitting novel cosmologies, including late-time de Sitter solutions in the absence of a cosmological constant. Deviations from Newton's law are predicted inside astrophysical bodies, which allow for falsifiable, smoking-gun tests of the theory. In this work we study the pulsations of stars by deriving and solving the wave equation governing linear adiabatic oscillations to find the modified period of pulsation. Using both semi-analytic and numerical models, we perform a preliminary survey of the stellar zoo in an attempt to identify the best candidate objects for testing the theory. Brown dwarfs and Cepheid stars are found to be particularly sensitive objects and we discuss the possibility of using both to test the theory.