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The possibility of primordial black hole direct detection
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Advisor(s)
Abstract(s)
This thesis explores the possibility of directly detecting blackbody emission from
Primordial Black Holes (PBHs). A PBH might form when a cosmological density
uctuation with wavenumber k, that was once stretched to scales much larger than
the Hubble radius during ination, reenters inside the Hubble radius at some later
epoch. By modeling these uctuations with a running{tilt power{law spectrum
(n(k) = n0 + a1(k)n1 + a2(k)n2 + a3(k)n3; n0 = 0:951; n1 = 0:055; n2 and n3
unknown) each pair (n2,n3) gives a di erent n(k) curve with a maximum value
(n+) located at some instant (t+). The (n+,t+) parameter space [(1:20,1023 s) to
(2:00,109 s)] has t+ = 1023 s{109 s and n+ = 1:20{2:00 in order to encompass the
formation of PBHs in the mass range 1015 g{1010M (from the ones exploding at
present to the most massive known). It was evenly sampled: n+ every 0.02; t+ every
order of magnitude. We thus have 41 33 = 1353 di erent cases. However, 820 of
these ( 61%) are excluded (because they would provide a PBH population large
enough to close the Universe) and we are left with 533 cases for further study.
Although only sub{stellar PBHs ( 1M ) are hot enough to be detected at large
distances we studied PBHs with 1015 g{1010M and determined how many might have formed and still exist in the Universe. Thus, for each of the 533 (n+,t+) pairs we determined the fraction of the Universe going into PBHs at each epoch ( ), the PBH density parameter (PBH), the PBH number density (nPBH), the total number of PBHs in the Universe (N), and the distance to the nearest one (d). As a
rst result, 14% of these (72 cases) give, at least, one PBH within the observable
Universe, one{third being sub{stellar and the remaining evenly spliting into stellar,
intermediate mass and supermassive. Secondly, we found that the nearest stellar
mass PBH might be at 32 pc, while the nearest intermediate mass and supermassive
PBHs might be 100 and 1000 times farther, respectively.
Finally, for 6% of the cases (four in 72) we might have substellar mass PBHs within
1 pc. One of these cases implies a population of 105 PBHs, with a mass of 1018 g(similar to Halley's comet), within the Oort cloud, which means that the nearest
PBH might be as close as 103 AU. Such a PBH could be directly detected with a
probability of 1021 (cf. 1032 for low{energy neutrinos). We speculate in this
possibility.
Description
Keywords
Black hole physics Early universe Cosmological parameters Oort cloud Dark matter Galaxy: halo Mathematics, speciality of Mathematical-Physics . Faculdade de Ciências Exatas e da Engenharia