Angular Momentum of Dark Matter Black Holes
  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.
