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Primordial black holes as DM candidates 
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#1
Jan2213, 03:03 PM

Sci Advisor
PF Gold
P: 9,488

This paper, Constraints on primordial black holes as dark matter candidates from capture by neutron stars  http://arxiv.org/abs/1301.4984, appears to just about seal the coffin on primordial black holes as dark matter candidates. It does an admirable job summarizing the mass constraints on primordial black holes as a dark matter candidate that have appeared in the literature. Tiny black holes [<10^16 gm] were ruled out decades ago because they would have already evaporated, or be too few for consistency with observational limits on the cosmic gamma ray background. Microlensing surveys of the galactic halo have significantly constrained the number of PBH's in the mass range of 10^26 to 10^34 gm, and WMAP, COBE and FIRAS have severely constrained the number of PBH's at higher masses. Collectively, these date have left a window of opportunity for PBH's as dark matter in the range of 10^16  10^26 gm. The results of this paper trims the allowable mass range to within an order of magnitude of 10^25 gm. Obviously, such a narrow mass range for PBH's as dark matter candidates would invoke fine tuning problems to explain their origin.



#2
Jan2313, 01:39 AM

P: 157

...I guess we are heading more on MACHo's, wimps, hypothetical Neutralinos, axioms, Photinos again Or the other way around 'modification of gravity MOND'. Or Particles of matter and antimatter with gravitational opposites(assuming the crazy hypothetical outcomes in quantizing gravity) the closest we can assume of dark matter origin.



#3
Jan2313, 08:45 AM

Astronomy
Sci Advisor
PF Gold
P: 23,274

Since the mass is small the classical horizon structure can be expected to be unrealistic, and the classicallyderived evaporation scenario especially so. As time goes on, we can expect to hear more about nonsingular primordial black holes as dark matter candidates, where the model of the black hole takes account of quantum effects. Here is an examplea paper published in Physical Review D, in 2010, that has been cited by 21 other papers. http://arxiv.org/abs/arXiv:0912.1823 ("A model for nonsingular black hole collapse and evaporation") Here is a followup paper from last year, by the same authors:http://arxiv.org/abs/arXiv:1202.0412 ("Emission spectra of selfdual black holes") Naturally the radiation signature from these nonsingular BH is different from that of singular BH, and the calculated evaporation rates, and the lifetimes, and the expected distribution of masses, etc. Here's a seminal paper on this topic, which now has 34 cites. http://arxiv.org/abs/arXiv:0811.2196 


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