33,922 research outputs found
White holes and eternal black holes
We investigate isolated white holes surrounded by vacuum, which correspond to
the time reversal of eternal black holes that do not evaporate. We show that
isolated white holes produce quasi- thermal Hawking radiation. The time
reversal of this radiation, incident on a black hole precursor, constitutes a
special preparation that will cause the black hole to become eternal.Comment: 5 pages, 2 figures, revtex; revised version to appear in Classical
and Quantum Gravit
Anomaly induced QCD potential and Quark Decoupling
We explore the anomaly induced effective QCD meson potential in the framework
of the effective Lagrangian approach. We suggest a decoupling procedure, when a
flavored quark becomes massive, which mimics the one employed by Seiberg for
supersymmetric gauge theories. It is seen that, after decoupling, the QCD
potential naturally converts to the one with one less flavor. We study the
and dependence of the mass.Comment: 11 pages, RevTe
Light weight fire resistant graphite composites
Composite structures with a honeycomb core and characterized by lightweight and excellent fire resistance are provided. These sandwich structures employ facesheets made up of bismaleimide-vinyl styrylpyridine copolymers with fiber reinforcement such as carbon fiber reinforcement. In preferred embodiments the facesheets are over layered with a decorative film. The properties of these composites make them attractive materials of construction aircraft and spacecraft
Metastable Cosmic Strings in Realistic Models
We investigate the stability of the electroweak Z-string at high
temperatures. Our results show that while finite temperature corrections can
improve the stability of the Z-string, their effect is not strong enough to
stabilize the Z-string in the standard electroweak model. Consequently, the
Z-string will be unstable even under the conditions present during the
electroweak phase transition. We then consider phenomenologically viable models
based on the gauge group and show
that metastable strings exist and are stable to small perturbations for a large
region of the parameter space for these models. We also show that these strings
are superconducting with bosonic charge carriers. The string superconductivity
may be able to stabilize segments and loops against dynamical contraction.
Possible implications of these strings for cosmology are discussed.Comment: 24 pages, 2 figures (available on request); HUTP-92/A032,
Fermilab-Pub-92/228-
Information, information processing and gravity
I discuss fundamental limits placed on information and information processing
by gravity. Such limits arise because both information and its processing
require energy, while gravitational collapse (formation of a horizon or black
hole) restricts the amount of energy allowed in a finite region. Specifically,
I use a criterion for gravitational collapse called the hoop conjecture. Once
the hoop conjecture is assumed a number of results can be obtained directly:
the existence of a fundamental uncertainty in spatial distance of order the
Planck length, bounds on information (entropy) in a finite region, and a bound
on the rate of information processing in a finite region. In the final section
I discuss some cosmological issues related to the total amount of information
in the universe, and note that almost all detailed aspects of the late universe
are determined by the randomness of quantum outcomes. This paper is based on a
talk presented at a 2007 Bellairs Research Institute (McGill University)
workshop on black holes and quantum information.Comment: 7 pages, 5 figures, revte
Tendency of spherically imploding plasma liners formed by merging plasma jets to evolve toward spherical symmetry
Three dimensional hydrodynamic simulations have been performed using smoothed
particle hydrodynamics (SPH) in order to study the effects of discrete jets on
the processes of plasma liner formation, implosion on vacuum, and expansion.
The pressure history of the inner portion of the liner was qualitatively and
quantitatively similar from peak compression through the complete stagnation of
the liner among simulation results from two one dimensional
radiationhydrodynamic codes, 3D SPH with a uniform liner, and 3D SPH with 30
discrete plasma jets. Two dimensional slices of the pressure show that the
discrete jet SPH case evolves towards a profile that is almost
indistinguishable from the SPH case with a uniform liner, showing that
non-uniformities due to discrete jets are smeared out by late stages of the
implosion. Liner formation and implosion on vacuum was also shown to be robust
to Rayleigh-Taylor instability growth. Interparticle mixing for a liner
imploding on vacuum was investigated. The mixing rate was very small until
after peak compression for the 30 jet simulation.Comment: 28 pages, 16 figures, submitted to Physics of Plasmas (2012
Multi-chord fiber-coupled interferometer with a long coherence length laser
This paper describes a 561 nm laser heterodyne interferometer that provides
time-resolved measurements of line-integrated plasma electron density within
the range of 10^15-10^18 cm^(-2). Such plasmas are produced by railguns on the
Plasma Liner Experiment (PLX), which aims to produce \mu s-, cm-, and
Mbar-scale plasmas through the merging of thirty plasma jets in a spherically
convergent geometry. A long coherence length, 320 mW laser allows for a strong,
sub-fringe phase-shift signal without the need for closely-matched probe and
reference path lengths. Thus only one reference path is required for all eight
probe paths, and an individual probe chord can be altered without altering the
reference or other probe path lengths. Fiber-optic decoupling of the probe
chord optics on the vacuum chamber from the rest of the system allows the probe
paths to be easily altered to focus on different spatial regions of the plasma.
We demonstrate that sub-fringe resolution capability allows the interferometer
to operate down to line-integrated densities of order 10^15 cm^(-2).Comment: submitted to Rev. Sci. Instrum. (2011
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