Gravitational Higgs Mechanism in Inspiraling Scalarized NS-WD Binary

Abstract

We investigate the gravitational Higgs mechanism in the inspiraling scalarized neutron star - white dwarf (NS-WD) binaries, whose dynamics are described by the scalar-tensor theory. Because of the difference in binding energy of NS and WD, the orbital decay of scalarized NS-WD system actually sources an emission of dipolar gravitational scalar radiation, in addition to the tensor gravitational waves, which breaks the Lorentz invariance constructed in the framework of general relativity. The resulted gravitational scalar radiation field obtains a scalar-energy-density-dependent effective mass, arising from a gravitational scalar potential that consists of a monotonically decreasing self-interactions of gravitational scalar field and an increasing exponential coupling between the scalar field and the NS/WD matter. Owing to a thin-ring-orbit effect, the gravitational interactions encoded by the massive scalar field is screened in the region of binary orbit, with high density of stars' scalar energy, which gives us the estimation for scalar masses of about $10^{-21} eV/c^2$ and leads to a Yulkawa-like correction to the Newtonian potential of the binary system. We demonstrate that the radiated gravitational tensor waves, propagating in the Yukawa type of potential, gain a scalar-background-dependent mass term of the order of $\sim 10^{-23} eV/c^2$.