139 research outputs found
Field theory simulation of Abelian-Higgs cosmic string cusps
We have performed a lattice field theory simulation of cusps in Abelian-Higgs
cosmic strings. The results are in accord with the theory that the portion of
the strings which overlaps near the cusp is released as radiation. The radius
of the string cores which must touch to produce the evaporation is
approximately in natural units. In general, the modifications to the
string shape due to the cusp may produce many cusps later in the evolution of a
string loop, but these later cusps will be much smaller in magnitude and more
closely resemble kinks.Comment: 9 pages, RevTeX, 13 figures with eps
Supersymmetry and primordial black hole abundance constraints
We study the consequences of supersymmetry for primordial black hole (PBH)
abundance constraints. PBHs with mass less than about 10^{11}g will emit
supersymmetric particles when they evaporate. In most models of supersymmetry
the lightest of these particles, the lightest supersymmetric particle (LSP), is
stable and will hence survive to the present day. We calculate the limit on the
initial abundance of PBHs from the requirement that the present day LSP density
is less than the critical density. We apply this limit, along with those
previously obtained from the effects of PBH evaporation on nucleosynthesis and
the present day density of PBHs, to PBHs formed from the collpase of
inflationary density perturbations, in the context of supersymmetric inflation
models. If the reheat temperature after inflation is low, so as to avoid the
overproduction of gravitinos and moduli, then the lightest PBHs which are
produced in significant numbers will be evaporating around the present day and
there are therefore no constraints from the effects of the evaporation products
on nucleosynthesis or from the production of LSPs. We then examine models with
a high reheat temperature and a subsequent period of thermal inflation. In
these models avoiding the overproduction of LSPs limits the abundance of low
mass PBHs which were previously unconstrained. Throughout we incorporate the
production, at fixed time, of PBHs with a range of masses, which occurs when
critical collapse is taken into account.Comment: 8 pages RevTeX file with 3 figures incorporated (uses RevTeX and
epsf). Version to appear in Phys. Rev. D: minor change to calculation and
added discussio
Evidence for two-step binding of reduced nicotinamide-adenine dinucleotide to aldehyde dehydrogenase
Relativistic Viscous Fluid Description of Microscopic Black Hole Wind
Microscopic black holes explode with their temperature varying inversely as
their mass. Such explosions would lead to the highest temperatures in the
present universe, all the way to the Planck energy. Whether or not a
quasi-stationary shell of matter undergoing radial hydrodynamic expansion
surrounds such black holes is been controversial. In this paper relativistic
viscous fluid equations are applied to the problem. It is shown that a
self-consistent picture emerges of a fluid just marginally kept in local
thermal equilibrium; viscosity is a crucial element of the dynamics.Comment: 11 pages, revte
NEUTRINOS FROM PRIMORDIAL BLACK HOLES
The emission of particles from black holes created in the early Universe has
detectable astrophysical consequences. The most stringent bound on their
abundance has been obtained from the absence of a detectable diffuse flux of
100 MeV photons. Further scrutiny of these bounds is of interest as they, for
instance, rule out primordial black holes as a dark matter candidate. We here
point out that these bounds can, in principle, be improved by studying the
diffuse cosmic neutrino flux. Measurements of near-vertical atmospheric
neutrino fluxes in a region of low geomagnetic latitude can provide a
competitive bound. The most favorable energy to detect a possible diffuse flux
of primordial black hole origin is found to be a few MeV. We also show that
measurements of the diffuse flux is the most promising to improve
the existing bounds deduced from gamma-ray measurements. Neutrinos from
individual black hole explosions can be detected in the GeV-TeV energy region.
We find that the kilometer-scale detectors, recently proposed, are able to
establish competitive bounds.Comment: 19 pages plus 9 uuencoded and compressed postscript figure
High Temperature Matter and Gamma Ray Spectra from Microscopic Black Holes
The relativistic viscous fluid equations describing the outflow of high
temperature matter created via Hawking radiation from microscopic black holes
are solved numerically for a realistic equation of state. We focus on black
holes with initial temperatures greater than 100 GeV and lifetimes less than 6
days. The spectra of direct photons and photons from decay are
calculated for energies greater than 1 GeV. We calculate the diffuse gamma ray
spectrum from black holes distributed in our galactic halo. However, the most
promising route for their observation is to search for point sources emitting
gamma rays of ever-increasing energy.Comment: 33 pages, 13 figures, to be submitted to PR
Investigation of Primordial Black Hole Bursts using Interplanetary Network Gamma-ray Bursts
The detection of a gamma-ray burst (GRB) in the solar neighborhood would have
very important implications for GRB phenomenology. The leading theories for
cosmological GRBs would not be able to explain such events. The final bursts of
evaporating Primordial Black Holes (PBHs), however, would be a natural
explanation for local GRBs. We present a novel technique that can constrain the
distance to gamma-ray bursts using detections from widely separated,
non-imaging spacecraft. This method can determine the actual distance to the
burst if it is local. We applied this method to constrain distances to a sample
of 36 short duration GRBs detected by the Interplanetary Network (IPN) that
show observational properties that are expected from PBH evaporations. These
bursts have minimum possible distances in the 10^13-10^18 cm (7-10^5 AU) range,
consistent with the expected PBH energetics and with a possible origin in the
solar neighborhood, although none of the bursts can be unambiguously
demonstrated to be local. Assuming these bursts are real PBH events, we
estimate lower limits on the PBH burst evaporation rate in the solar
neighborhood.Comment: Accepted to the Astrophysical Journal (9 Figures, 3 Tables
Spectral Lags of Gamma-Ray Bursts from Primordial Black Hole (PBH) Evaporations
Primordial Black Holes (PBHs), which may have been created in the early
Universe, are predicted to be detectable by their Hawking radiation. PBHs with
an initial mass of 5.0 * 10^14 g should be expiring today with a burst of high
energy particles. Evaporating PBHs in the solar neighborhood are candidate
Gamma-Ray Bursts (GRBs) progenitors. We propose spectral lag, which is the
temporal delay between the high energy photon pulse and the low energy photon
pulse, as a possible method to detect PBH evaporation events with the Fermi
Gamma-ray Space Telescope Observatory.Comment: 3 pages; Published in the proceedings of Huntsville 2008 symposium on
GRBs; Indices in Equation 7 and 8 correcte
Primordial black holes under the double inflationary power spectrum
Recently, it has been shown that the primordial black holes (PBHs) produced
by near critical collapse in the expanding universe have a scaling mass
relation similar to that of black holes produced in asymptotically flat
spacetime. Distinct from PBHs formed with mass about the horizon mass (Type I),
the PBHs with the scaling relation (Type II) can be created with a range of
masses at a given formation time. In general, only the case in which the PBH
formation is concentrated at one epoch has been considered. However, it is
expected that PBH formation is possible over a broad range of epochs if the
density fluctuation has a rather large amplitude and smooth scale dependence.
In this paper, we study the PBH formation for both types assuming the power
spectrum of double inflationary models in which the small scale fluctuations
could have large amplitudes independent of the CMBR anisotropy. The mass
spectrum of Type II PBHs is newly constructed without limiting the PBH
formation period. The double inflationary power spectrum is assumed to be of
double simple power-law which are smoothly connected. Under the assumed power
spectrum, the accumulation of small PBHs formed at later times is important and
the mass range is significantly broadened for both Types. The PBH mass spectra
are far smoother than the observed MACHO spectrum due to our assumption of a
smooth spectrum. In order to fit the observation, a more spiky spectrum is
required.Comment: 7 pages including 2 figures, to be published in Phys. Rev.
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