Cosmological boost factor for dark matter annihilation at redshifts of z =10 100 using the power spectrum approach
Abstract
We compute the cosmological boost factor at high redshifts of z =10  100 by integrating the nonlinear matter power spectrum measured from highresolution cosmological N body simulations. An accurate boost factor is required to estimate the energy injection from dark matter annihilation, which may affect the cosmological reionization process. We combined various boxsize simulations (side lengths of 1 kpc10 Mpc) to cover a wide range of scales, i.e., k =1  10^{7} Mpc^{1} . The boost factor is consistent with the linear theory prediction at z ≳50 but strongly enhanced at z ≲40 as a result of nonlinear matter clustering. Although dark matter freestreaming damping was imposed at k_{fs}=10^{6} Mpc^{1} in the initial power spectrum, the damping disappears at later times of z ≲40 as a result of the power transfer from large to small scales. Because the simulations do not explore very smallscale clustering at k >10^{7} Mpc^{1}, our result is a lower bound on the boost factor at z ≲40 . A simple fitting function of the boost factor is also presented.
 Publication:

Physical Review D
 Pub Date:
 November 2021
 DOI:
 10.1103/PhysRevD.104.103518
 arXiv:
 arXiv:2107.00897
 Bibcode:
 2021PhRvD.104j3518T
 Keywords:

 Astrophysics  Cosmology and Nongalactic Astrophysics;
 General Relativity and Quantum Cosmology;
 High Energy Physics  Phenomenology
 EPrint:
 12 pages, 5 figures, accepted for publication in PRD