Impact of kinetic and potential selfinteractions on scalar dark matter
Abstract
We consider models of scalar dark matter with a generic interaction potential and noncanonical kinetic terms of the Kessence type that are subleading with respect to the canonical term. We analyze the lowenergy regime and derive, in the nonrelativistic limit, the effective equations of motions. In the fluid approximation they reduce to the conservation of matter and to the Euler equation for the velocity field. We focus on the case where the scalar field mass 10^{21}≪m ≲10^{4} eV is much larger than for fuzzy dark matter, so that the quantum pressure is negligible on cosmological and galactic scales, while the selfinteraction potential and noncanonical kinetic terms generate a significant repulsive pressure. At the level of cosmological perturbations, this provides a darkmatter densitydependent speed of sound. At the nonlinear level, the hydrostatic equilibrium obtained by balancing the gravitational and scalar interactions imply that virialized structures have a solitonic core of finite size depending on the speed of sound of the dark matter fluid. For the most relevant potential in λ_{4}ϕ^{4}/4 or Kessence with a (∂ϕ )^{4} interaction, the size of such stable cores cannot exceed 60 kpc. Structures with a density contrast larger than 1 0^{6} can be accommodated with a speed of sound c_{s}≲10^{6}. We also consider the case of a cosine selfinteraction, as an example of bounded nonpolynomial selfinteraction. This gives similar results in lowmass and lowdensity halos whereas solitonic cores are shown to be absent in massive halos.
 Publication:

Physical Review D
 Pub Date:
 July 2019
 DOI:
 10.1103/PhysRevD.100.023526
 arXiv:
 arXiv:1906.00730
 Bibcode:
 2019PhRvD.100b3526B
 Keywords:

 Astrophysics  Cosmology and Nongalactic Astrophysics;
 General Relativity and Quantum Cosmology
 EPrint:
 25 pages