Sigh! Probably Because the Dark Matter IS Primordial Black Holes
Mike Hawkins has offered a cogent empirically-supported case for stellar-mass and planetary-mass ultracompacts (with primordial black holes being the most likely candidates) as the mystery objects causing microlensing events seen in bulge, halo and QSO research. [papers available for free at the arxiv preprint repository, 2011 and 2015]. A huge population of primordial black holes satisfies the non-baryonic constraint, might also explain where cosmic rays primarily come from, and might explain why the ARCADE-2 experiment found a unexplained factor-of-6 excess in cosmological radio emission. Primordial black holes also might constitute the sources of the approximately 6,000/day Fast Radio Bursts that have been discovered/inferred in the last few years by several astrophysical research groups (Science News, Aug. 9, 2014 issue; many papers subsequently posted to the arxiv preprint repository).
The recent detection of 2 (possibly 3) gravitational wave events suggests that there is a large population of stellar-mass black holes that has yet to be fully discovered. Some astrophysicists have again proposed that primordial stellar-mass black holes make an excellent candidate population for the dark matter.
Not long ago microlensing research (MOA group) identified at least 0.1 trillion unbound planetary-mass objects in unknown physical states (Suni et al, Nature, May, 2011). Astrophysicists have also discovered an estimated 70 billion brown dwarf objects in the thin disk of the Galaxy. Since the thin disk represents a very small fraction of the Galaxy’s volume, one can be reasonably sure that 70,000,000,000 is a lower limit. Recently we have also discovered 100s of thousands of ultracompact mystery objects in the Milky Way Galaxy central region. In addition researchers have just found evidence that a globular cluster of stars contains on the order of 100 stellar-mass black holes instead of the expected few (Pueten et al, Mon. Not. Royal Astr. Soc., 2016). That would possibly mean another 10,000 to 100,000 stellar-mass black holes per galaxy beyond those already accounted for.
So let’s see: trillions of unbound planetary-mass nomads and >70 billion brown dwarfs and 100s of billions of stellar-mass MACHO objects. That’s a significant percentage of the total dark matter population, and it is a minimum estimate! Can we understand why the majority of theoretical physicists and the scientific press ignore observed stellar scale dark matter candidates, and only emphasize mythical particles like WIMPs and axions that have never been observed? It seems like a dubious and unscientific obsession.
It is a scientific error to assume, as most theoretical physicists do, that the dark matter absolutely must be composed of hypothetical subatomic particles. A scientist maintains an open mind, in word and deed. Moreover, a scientist does not condone denial of important and confirmed empirical results.
R.L. Oldershaw
http://www3.amherst.edu/~rloldershaw
Discrete Scale Relativity/Fractal Cosmology
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