[ExI] Dark Matter

John Clark johnkclark at gmail.com
Tue Sep 6 00:49:23 UTC 2016

There are 2 recent papers
​about Primordial ​Black Holes and Dark Matter, both are in
Physical Review Letters
​. In one ​
John Hopkins University
​ scientists say the rate that LIGO discovered ​Black Hole mergers is
consistent with Dark Matter being made entirely of Primordial Black Holes.


In the other paper Kyoto University scientists say the discovery rate can
account for some but not all of Dark Matter, so there must be something
else in addition.


The difference between the 2 papers comes from different assumptions about
the very early universe less than a second after the Big Bang and the rate
Black Holes would be formed in pairs. Both agree that Primordial Black
Holes would tend to have more elliptical orbits than astrophysical ones
formed from dead stars which would usually be more circular, and LIGO can
tell the difference. We need more data and fortunately LIGO should come
back online any day now, and VIRGO in Italy too, so before long we should
know who is right.

Another Dark matter candidate is a hypothetical light particle, the Axion.
Recently Maurizio Giannotti suggested that the observed unexpected rapid
cooling of white dwarfs and neutron stars could be explained by the stars
radiating away energy in the form of Axions. One good thing about Axions is
that unlike WIMPS the Axions theory doesn't have a lot of wiggle room, so
within a few years the Axion Dark Matter Experiment (ADMX) should be able
to find Axions or prove they don't exist. Unlike WIMPS Axions react
(weakly) with a magnetic fields and cause a Axion to be converted to a
microwave photon which can be detected by ADMX, assuming Axions are not
just the figment of a physicist's imagination.

In another development that may or may not be related to Dark Matter there
is increasing evidence (although not yet proof) of a
fifth fundamental force that effects only electrons and neutrons and only
at very close range:


  John K Clark

While astrophysical black holes have circular orbits, those of primordial
black holes should be elliptical, which would provide a way to distinguish
between the two when their shudders of gravitational energy are detected on
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