170 research outputs found
The form of cosmic string cusps
We classify the possible shapes of cosmic string cusps and how they transform
under Lorentz boosts. A generic cusp can be brought into a form in which the
motion of the cusp tip lies in the plane of the cusp. The cusp whose motion is
perpendicular to this plane, considered by some authors, is a special case and
not the generic situation.
We redo the calculation of the energy in the region where the string overlaps
itself near a cusp, which is the maximum energy that can be released in
radiation. We take into account the motion of a generic cusp and the resulting
Lorentz contraction of the string core. The result is that the energy scales as
instead of the usual value of , where is the
string radius and and is the typical length scale of the string. Since for cosmological strings, the radiation is strongly suppressed and could
not be observed.Comment: 15 pages, ReVTex, 2 postscript figures with eps
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
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
Constraints on Cosmic Strings due to Black Holes Formed from Collapsed Cosmic String Loops
The cosmological features of primordial black holes formed from collapsed
cosmic string loops are studied. Observational restrictions on a population of
primordial black holes are used to restrict , the fraction of cosmic string
loops which collapse to form black holes, and , the cosmic string
mass-per-unit-length. Using a realistic model of cosmic strings, we find the
strongest restriction on the parameters and is due to the energy
density in photons radiated by the black holes. We also find that
inert black hole remnants cannot serve as the dark matter. If earlier, crude
estimates of are reliable, our results severely restrict , and
therefore limit the viability of the cosmic string large-scale structure
scenario.Comment: (Plain Tex, uses tables.tex -- wrapped lines corrected), 11 pages,
FERMILAB-Pub-93/137-
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