Phenomenology of wavelike vector dark matter nonminimally coupled to gravity

Abstract

We study three astrophysical/cosmological consequences of nonminimal couplings to gravity in wavelike vector dark matter. In the nonrelativistic limit, the nonminimal coupling with the lowest mass dimension leads to effective self-interactions that affect the mass-radius relation of vector solitons, growth of linear perturbations during structure formation, and the speed of gravitational waves (GWs). Based on the success of cold dark matter on large-scale perturbations and the current limits on GW speed, we constrain the dark matter mass and nonminimal coupling strength to be within the range |ξ 1|/m 2 ≪ 1050 eV-2 and -3 × 1046 eV-2 ≲ ξ 2/m 2 ≲ 8 × 1048 eV-2.

Vector dark matter, inflation, and non-minimal couplings with gravity

“…7 We note that following an effective fluid approach in the non-relativistic regime of vector DM, the speed of GWs has been shown to be modified for which constraints by the recent binary Neutron star merger event [54,55] applies, see eq. (3.16) in [25]. We note that these constraints do not effect the parameter space of our setup because for fA L → 1, (5.5) gives α/m ≃ 3 × 10 −22 eV −1 (m/eV) 1/4 satisfying eq.…”

“…We note that these constraints do not effect the parameter space of our setup because for fA L → 1, (5.5) gives α/m ≃ 3 × 10 −22 eV −1 (m/eV) 1/4 satisfying eq. (3.16) of [25] for all mass (5.6) and α (6.1) values that realize DM abundance in the form of longitudinal modes. 8 Recall that the longitudinal vector degrees of freedom correspond to iso-curvature fields, see section 3.3.…”

“…In this case, CDM perturbations may exhibit an instability for a certain combination of non-minimal couplings with the vector field, see e.g. [25]. Finding the evolution of the corresponding perturbations are outside the scope of this work, however the special form of the non-minimal coupling we consider might suggest that such instabilities are absent in our setup where 2ξ1 + ξ2 = 0 following the notation of [25].…”

“…[25]. Finding the evolution of the corresponding perturbations are outside the scope of this work, however the special form of the non-minimal coupling we consider might suggest that such instabilities are absent in our setup where 2ξ1 + ξ2 = 0 following the notation of [25]. 7 We note that following an effective fluid approach in the non-relativistic regime of vector DM, the speed of GWs has been shown to be modified for which constraints by the recent binary Neutron star merger event [54,55] applies, see eq.…”

“…The dark photon cosmological evolution has distinctive properties, see e.g. [20][21][22][23][24][25]. It can have testable effects when surrounding black holes, or forming cosmic strings, see e.g.…”