Abstract
The putative black holes which may constitute all the dark matter are described by a Kerr metric with only two parameters, mass M and angular momentum J. There has been little discussion of J since it plays no role in the upcoming attempt at detection by microlensing. Nevertheless J does play a central role in understanding the previous lack of detection, especially of CMB distortion. We explain why bounds previously derived from lack of CMB distortion are too strong for primordial black holes with J non-vanishing. Almost none of the dark matter black holes can be from stellar collapse, and nearly all are primordial, to avoid excessive CMB distortion.
Highlights
The Milky Way galaxy in which we reside lies within a large approximately spherical halo of dark matter (DM) which does not experience the strong or electromagnetic interactions, nor as we shall assume here the weak interactions
The popular idea that the dark matter constituent is a WIMP with weak interactions was born out of supersymmetry which lacks any support from extensive LHC data on pp scattering which probed the energy regime where signs of SUSY were most expected
The plum pudding model for the dark halo proposed in [3] arose from a confluence of theoretical threads including study of the entropy of the universe and the knowledge of how to form PBHs with many solar masses as in Eqs. (1) and (5). It was the weakening of the argument for WIMPs which was most decisive, The strongest objection to the MACHOs in [3] has been based on the X-rays and the CMB distortion as calculated by ROM [9]
Summary
The Milky Way galaxy in which we reside lies within a large approximately spherical halo of dark matter (DM) which does not experience the strong or electromagnetic interactions, nor as we shall assume here the weak interactions. With no WIMP one is led to astrophysical MACHOs and confronted with the constraint from BBN that no more than 20% of the DM can be baryonic This means that to make 100% of the DM we cannot use compact objects such as white dwarfs, neutron stars, brown dwarfs and unassociated planets. We shall discuss the higher mass range Eq( 5) later in the paper For this Introduction, we recall that in a microlensing experiment, e.g. using the LMC or SMC for convenient sources, microlensing by halo PIMBHs, and assuming a typical transit velocity 200km.s−1, the time duration of the microlensing light curve can be estimated [7] to be approximately τ ≃ MP IMBH 2 years (6). The highest duration such light curve detected by the MACHO Collaboration which published in the year 2000 [1] corresponded to MP IMBH ≃ 20M⊙
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