Abstract

We explore in detail the possibility that gravitational wave signals from binary inspirals are affected by a new force that couples only to dark matter particles. We discuss the impact of both the new force acting between the binary partners as well as radiation of the force carrier. We identify numerous constraints on any such scenario, ultimately concluding that observable effects on the dynamics of binary inspirals due to such a force are not possible if the dark matter is accrued during ordinary stellar evolution. Constraints arise from the requirement that the astronomical body be able to collect and bind at small enough radius an adequate number of dark matter particles, from the requirement that the particles thus collected remain bound to neutron stars in the presence of another neutron star, and from the requirement that the theory allows old neutron stars to exist and retain their charge. Thus, we show that any deviation from the predictions of general relativity observed in binary inspirals must be due either to the material properties of the inspiraling objects themselves, such as a tidal deformability, to a true fifth force coupled to baryons, or to a non-standard production mechanism for the dark matter cores of neutron stars. Viable scenarios of the latter type include production of dark matter in exotic neutron decays, or the formation of compact dark matter objects in the early Universe that later seed star formation or are captured by stars.

Highlights

  • We explore in detail the possibility that gravitational wave signals from binary inspirals are affected by a new force that couples only to dark matter particles

  • We show that any deviation from the predictions of general relativity observed in binary inspirals must be due either to the material properties of the inspiraling objects themselves, such as a tidal deformability, to a true fifth force coupled to baryons, or to a non-standard production mechanism for the dark matter cores of neutron stars

  • Stringent constraints exist on a new fifth force coupled to baryons, see for instance refs. [24,25,26,27,28] and references therein, which have motivated a particular focus on the possibility of a new long-range force, mediated by ultra-light bosons, that couples only to dark matter or other cosmologically stable hidden sector particles residing inside neutron stars

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Summary

Inspirals and fifth-forces

Before turning to the constraints on the interactions of any exotic hidden sector particle, we first illustrate the necessary conditions for an observable new physics signal at LIGO/VIRGO. We assume that the new force couples only to dark sector particles. In order for it to act over sufficiently long distances of order 100 km, the mediator must be ultra-light ( 10−12 eV), and the dark sector particles must neither significantly screen the new force nor efficiently self-annihilate. Let us consider a binary neutron star system, and let us assume that each of the binary partners contains a population of dark sector particles. These populations will affect the inspiral dynamics in two distinct ways: first, the exotic force acting between them will affect the time evolution of the distance between the neutron stars, their orbital frequency, and the time of the merger. Radiation of the new light force carriers provides an extra energy loss mechanism

Effects of a new Yukawa force
Ultra-light boson radiation
Constraints on repulsive forces
Binding potential for DM particles
Size of the dark core
Constraints on dark core production via particle accretion
Constraints on dark core production in supernovae
Constraints on dark core production via neutron decay
Constraints on attractive forces
Black hole formation
Expulsion of the dark core
Constraints on dark core production mechanisms
Conclusions
Findings
A Capture rate calculation
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