TR: Why Black Holes May Constitute All Dark Matter

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TR: Why Black Holes May Constitute All Dark Matter

Post by bystander » Mon Mar 22, 2010 4:07 pm

Why Black Holes May Constitute All Dark Matter
Technology Review: physics arXiv blog: 2010 March 22
No Earth-based experiments have spotted any sign of dark matter-type particles. Perhaps that's because dark matter is an entirely different kind thing.

Dark matter is the mysterious stuff that cosmologists believe fills our Universe. The evidence for its existence is that there is not enough visible mass to hold galaxies together. But since galaxies manifestly do not fly apart, there must be some invisible stuff, some missing mass, that generates the gravitational forces holding them together.

But there's a problem with this idea. Two of them actually. First, physicists' best guess at the laws of physics give a good description of all of the particles they've discovered so far and a few they expect to discover soon. The trouble is that none of these particles have the right kind of properties to be dark matter ie electrically neutral, long-lived and slow moving. But none of the known or reasonably hypothesised particles fits the bill. To make room for a dark matter particle, the laws of physics have to be changed in ways that many theorists feel uncomfortable with.

Second, despite a decade spent searching for dark matter with experiments costing tens of millions of dollars, nobody has laid eyes on the stuff. Most physicists think these experiments have found nothing: zip, zilch, zero.

It's hard to escape the conclusion that some other explanation for the missing mass is needed.
Primordial Black Holes as All Dark Matter
We argue that a primordial black hole is a natural and unique candidate for all dark matter. We show that, in a smooth-hybrid new double inflation model, a right amount of the primordial black holes, with a sharply-defined mass, can be produced at the end of the smooth-hybrid regime, through preheating. We first consider masses < 10^(-7)M_sun which are allowed by all the previous constraints. We next discuss much heavier mass 10^5 M_sun hinted at by entropy, and galactic size evolution, arguments. Effects on the running of the scalar spectral index are computed.
Black Holes Constitute All Dark Matter
  • > astro-ph > arXiv:1003.3356v1 > 2010 Mar 17
The dimensionless entropy , S S/k, of the visible universe, taken as a sphere of radius 50 billion light years with the Earth at its ”center”, is discussed. An upper limit (10112), and a lower limit (10102), for S are introduced. It is suggested that intermediate-mass black holes (IMBHs) constitute all dark matter, and that they dominate S.