WIMPs and stellar-mass primordial black holes are incompatible

Abstract

We recently showed that postulated ultracompact minihalos with a steep density profile do not form in realistic simulations with enhanced initial perturbations. In this paper we assume that a small fraction of the dark matter consists of primordial black holes (PBHs) and simulate the formation of structures around them. We find that in this scenario halos with steep density profiles do form, consistent with theoretical predictions. If the rest of the dark matter consists of weakly interacting massive particles (WIMPs), we also show that WIMPs in the dense innermost part of halos surrounding the PBH would annihilate and produce a detectable gamma-ray signal. The non-detection of this signal implies that PBHs make up at most one billionth of the dark matter, provided that their mass is greater than one millionth of the mass of the Sun. Similarly, a detection of PBHs would imply that the remaining dark matter could not be WIMPs.

Generalized covariant prescriptions for averaging cosmological observables

“…(3.10)-(3.13), including in the geometry (expressed in GLC form) all contributions arising from the Bardeen potential ψ, up to first order. Following the procedure (and the results) of previous papers (see in particular [26], where similar computations have been performed by consistently including all second order perturbative contributions) we thus expand the coordinate transformation as y µ (x) = y µ (0) +y µ (1) +· · · , and linearize the perturbed GLC metric by defining Υ = Υ (0) +Υ (1) ,…”

“…Here Φ F LRW is the unperturbed value of Φ computed in the FLRW metric background, and the corresponding fractional correction f Φ (z) is given by [21] f Φ (z) = δΦ (2) 0 + δµ (1) δΦ (1) 0 − δµ (1) 0 δΦ (1) 0 , (4.9)…”

“…where δµ (1) is the same term appearing in Eq. (4.9), arising from the perturbations of the measure (3.12).…”

“…For instance, the possible impact of small scale inhomogeneities on the large scale dynamics cannot be properly addressed without using a well-posed prescription for averaging their contribution to the cosmological equations. In addition, recent results in the context of numerical relativity have stressed the need for a full theoretical control on the choice of the averaging procedure [1]. Starting with the right choice is crucial for reaching the sought level of precision (or, more ambitiously, for writing the correct numerical code) in the context of modern cosmological simulations [2][3][4][5].…”

The evolution of primordial black holes and their final observable spins

“…In such a mass range, there are already stringent bounds on the fraction of DM composed by PBHs, see for example [12]. Thus one is forced to consider the accretion onto PBHs in the presence of an additional DM component which forms a dark halo of mass M h , truncated at a radius r h given by (assuming a power law density profile ρ ∝ r −α , with approximately α 2.25) [53,54] which is plotted in Fig. 1 and obtained following the procedure reported in Appendix B, including the relevant estimate of the relative velocity v rel .…”