Gravitomagnetic tidal response of relativistic stars in partially screened scalar-tensor theories

TL;DR

This paper explores how partial Vainshtein screening in scalar-tensor theories affects the gravitomagnetic tidal response of relativistic stars, revealing deviations from general relativity that depend on specific model parameters.

Contribution

It introduces a calculation of gravitomagnetic tidal Love numbers in a higher-order scalar-tensor gravity model, highlighting the complexity of characterizing tidal responses beyond general relativity.

Findings

Deviations from GR increase with higher multipoles and compactness.

Parameters alone do not fully determine the tidal response.

Partial Vainshtein screening influences the gravitomagnetic tidal Love numbers.

Abstract

In scalar-tensor theories beyond Horndeski, the Vainshtein screening mechanism is only partially effective inside astrophysical bodies. We investigate the potential to detect this partial breaking of Vainshtein screening through the tidal response of fluid bodies. We calculate the gravitomagnetic tidal Love numbers in a specific model of degenerate higher-order scalar-tensor gravity and analyze how deviations from general relativity depend on parameters governing the breaking of Vainshtein screening in the weak-gravity regime. For fixed parameter values, the relative deviations increase with higher multipoles and larger compactness. However, we demonstrate that these parameters alone are insufficient to fully characterize the tidal response of relativistic bodies in scalar-tensor theories beyond Horndeski.