No evidence of kinetic screening in simulations of merging binary neutron stars beyond general relativity

TL;DR

This study uses advanced relativistic simulations to investigate scalar-tensor theories in binary neutron star mergers, finding that screening suppresses dipole but not quadrupole scalar emissions, with potential detectability comparable to Brans-Dicke theories.

Contribution

First comprehensive relativistic simulation of binary neutron star mergers in scalar-tensor theories with screening, revealing the behavior of scalar emissions during merger.

Findings

Screening suppresses dipole scalar emission.

Quadrupole scalar signals can be as large as in Brans-Dicke theories.

No evidence of kinetic screening in the simulated mergers.

Abstract

We have conducted fully relativistic simulations in a class of scalar-tensor theories with derivative self-interactions and screening of local scales. By using high-resolution shock-capturing methods and a non-vanishing shift vector, we have managed to avoid issues plaguing similar attempts in the past. We have first confirmed recent results by ourselves in spherical symmetry, obtained with an approximate approach and pointing at a partial breakdown of the screening in black-hole collapse. Then, we considered the late inspiral and merger of binary neutron stars. We found that screening tends to suppress the (subdominant) dipole scalar emission, but not the (dominant) quadrupole scalar mode. Our results point at quadrupole scalar signals as large as (or even larger than) in Fierz-Jordan-Brans-Dicke theories with the same conformal coupling, for strong-coupling scales in the MeV range that we can simulate.