Primordial black holes

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Primordial black holes

• B. Czerny
• Copernicus Astronomical Center, Warsaw
• on behalf of collaboration D. Cline, B. Czerny,
  A. Dobrzycki, A. Janiuk, C. Matthey, M.
  Nikolajuk, S. Otwinowski

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Introduction
The existence of the primary black holes is an
unproved but a very interesting possibility.
Their detection, or their absence, will impose
important constraints on the physics of the early
Universe, nature of the dark mass constituting
the dominant part of the matter, the origin of
the high energy radiation and cosmic rays, and
finally on the quantum gravity. Primary black
holes were supposed to form during the early
stage of the Big Bang. In standard 4-dimensional
approach their formation epoch t_0, their
expected lifetime, t_1, and the temperature of
their Hawking emission are given by the following
expressions
The existence of higher dimensions modify this
predictions. Therefore, in our search for
primordial black holes we have to allow for a
broad range of their properties.
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Scenarios of PBH formation

• Several possibilities are discussed in the
  literature (see eg. Carr 2005)
• inhomogeneities formed during the inflation
  epoch
• epoch of soft equation of state
• collapse of cosmic loops
• bubble collisions
• collapse of domain walls
• All these mechanisms give different expectations
  as for the range of masses produced. For example,
  soft state phase and bubbles of broken symmetry
  creates black holes with a narrow mass range,
  domain walls lead to brod range of masses with
  fractal structure while inhomogeneities give
  broad power law distributions.

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Where can we see now PBH?

• Several plausible hypothesis were brought in so
  far
• PBH constiture the dark mass, i.e. are seen
  through its gravitational effect
• some PBH evaporate now and
• are seen as some
  type gamma of ray emission
• produce cosmic
  rays
• On the other hand, PBH are by no means the only
  explanation of these phenomena so carefull
  analysis is needed in order to establish whether
  PBH can contribute, or must contribute, to these
  phenomena. Several results were already obtained
  with respect to this issue.

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Present observational constraints on PBH

• Mmin 1 g from the CMB quadrupole moment limit
  to the reheat temperature
• Dark mass PBH in the mass range 1017-1020 g are
  excluded by lack of femtolensing in gamma-ray
  bursts
• Dark mass PBH in the mass range 1026-1034 g are
  excluded by lack of microlensing in LMC stars
  (Alcock et al. 2001)
• Present evaporation rate of 1015 g PBH consistent
  with COMPTEL and EGRET data is 2.5 x 10-14 ? pc-3
  yr-1 (Green et al. 2001). The local overdensity
  factor consistent with PBH constituting dark halo
  is ?2x105.

We plan to estimate the density of the more
massive black holes at the basis of their X-ray
and gamma-ray radiation due to accretion of the
interstellar/intergalactic material. Preliminary
formula for a total luminosity of the dark halo
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Are any of GRB caused by PBH?

• We have found that a significant fraction of the
  Very Short Gamma Ray Bursts (T90 lt 0.1 s) show
  very peculiar properties
• they concentrate strongly in 1/8 of the sky in
  the BATSE data
• they are much harder, with emission extending
  beyond 5 MeV
• they probably do not have strong X-ray
  afterglow, unlike (some) SWIFT VSB events
• Many such events are seen in KONUS data but
  without localization.

Enhanced number of VSB in BATSE data are comming
from the anticenter region, unlike SWIFT/HETE2
events with afterglows (Cline et al. in
preparation).
Cline et al. 1999, 2005
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Are any of GRB caused by PBH?
V/Vmax test shows that this class of bursts is
not located at cosmological distances. Spectral
properties are consistent with expectation of the
evaporation of PBH. If so, the bursts are located
at a distance of about 100 pc, for a 4-d black
hole mass. Emission must be slightly beamed to
satisfy the occurance frquency of Green et al.
(2001). Anisotropy is an interesting aspect,
consistent with the results of the Millenium
cosmological simulations of the dark matter
perturbations which predict significant
clumpiness of dark matter.
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Tests based on dark matter structure

• There are plans to perform detailed studies of
  the dark matter distribution in galaxies using
  the SALT ground telescope facility.
• The target classes of objects
• dwarf galaxies (Lokas et al.)
• Low Surface Brightness Galaxies (Czerny et al.)