1,691 research outputs found
Evaporation of Schwarzschild Black Holes in Matrix Theory
Recently, in collaboration with Susskind, we proposed a model of
Schwarzschild black holes in Matrix theory. A large Schwarzschild black hole is
described by a metastable bound state of a large number of D0-branes which are
held together by a background, whose structure has so far been understood only
in 8 and 11 dimensions. The Hawking radiation proceeds by emission of small
clusters of D0-branes. We estimate the Hawking rate in the Matrix theory model
of Schwarzschild black holes and find agreement with the semiclassical rate up
to an undetermined numerical coefficient of order 1.Comment: 9 pages, harvma
Schwarzchild Black Holes in Matrix Theory II
We present a crude Matrix Theory model for Schwarzchild black holes in
uncompactified dimension greater than . The model accounts for the size,
entropy, and long range state interactions of black holes. The key feature of
the model is a Boltzmann gas of D0 branes, a concept which depends on certain
qualitative features of Matrix Theory which have not previously been utilized
in studies of black holes.Comment: 20 pages,harvmac,big, Some Typos corrected, 1 reference adde
Light Sheets and the Covariant Entropy Conjecture
We examine the holography bound suggested by Bousso in his covariant entropy
conjecture, and argue that it is violated because his notion of light sheet is
too generous. We suggest its replacement by a weaker bound.Comment: 5 pages, to appear in Classical and Quantum Gravit
Fractal Holography: a geometric re-interpretation of cosmological large scale structure
The fractal dimension of large-scale galaxy clustering has been demonstrated
to be roughly from a wide range of redshift surveys. If correct,
this statistic is of interest for two main reasons: fractal scaling is an
implicit representation of information content, and also the value itself is a
geometric signature of area. It is proposed that the fractal distribution of
galaxies may thus be interpreted as a signature of holography (``fractal
holography''), providing more support for current theories of holographic
cosmologies. Implications for entropy bounds are addressed. In particular,
because of spatial scale invariance in the matter distribution, it is shown
that violations of the spherical entropy bound can be removed. This holographic
condition instead becomes a rigid constraint on the nature of the matter
density and distribution in the Universe. Inclusion of a dark matter
distribution is also discussed, based on theoretical considerations of possible
universal CDM density profiles.Comment: 13 pp, LaTeX. Revised version; to appear in JCA
A covariant entropy conjecture on cosmological dynamical horizon
We here propose a covariant entropy conjecture on cosmological dynamical
horizon. After the formulation of our conjecture, we test its validity in
adiabatically expanding universes with open, flat and closed spatial geometry,
where our conjecture can also be viewed as a cosmological version of the
generalized second law of thermodynamics in some sense.Comment: JHEP style, 9 pages, 1 figure, typos corrected, accepted for
publication in JHE
Charged Black Holes in Two-Dimensional String Theory
We discuss two dimensional string theories containing gauge fields introduced
either via coupling to open strings, in which case we get a Born-Infeld type
action, or via heterotic compactification. The solutions to the modified
background field equations are charged black holes which exhibit interesting
space-time geometries. We also compute their masses and charges.Comment: 39 page
Central Venous Catheter Infection with Brevibacterium sp. in an Immunocompetent Woman: Case Report and Review of the Literature
Brevibacterium spp. were considered apathogenic until a few reports of infections in immunocompromised patients were published. Herein, we present a case of a catheter-related septicemia with Brevibacterium casei in an immunocompetent patient receiving continuous iloprost infusion for pulmonary arterial hypertension and review the clinical presentation of this mainly emerging opportunistic pathoge
Electromagnetic Contributions to the Schiff Moment
The Schiff moment, \smij, is a parity and time reversal violating
fermion-fermion coupling. The nucleus-electron Schiff moment generically gives
the most important contribution to the electric dipole moments of atoms and
molecules with zero net intrinsic electronic spin and nuclear spin . Here, the electromagnetic contribution to the Schiff moment, \emij, is
considered. For a nucleon, the leading chirally violating contribution to this
interaction is calculable in the chiral limit in terms of the parity and time
reversal violating pion-nucleon coupling. For the Schiff moment of heavy
nuclei, this chiral contribution is somewhat smaller than the finite size
effect discussed previously in the literature.Comment: 7 pages, 1 figure (not included), Tex file, requires phyzzx, preprint
SCIPP 93/4
A Non-Supersymmetric Open String Theory and S-Duality
A non-supersymmetric ten-dimensional open string theory is constructed as an
orbifold of type I string theory, and as an orientifold of the bosonic type B
theory. It is purely bosonic, and cancellation of massless tadpoles requires
the gauge group to be SO(32)xSO(32). The spectrum of the theory contains a
closed string tachyon, and open string tachyons in the (32,32) multiplet. The
D-branes of this theory are analyzed, and it is found that the massless
excitations of one of the 1-branes coincide with the world-sheet degrees of
freedom of the D=26 bosonic string theory compactified on the SO(32) lattice.
This suggests that the two theories are related by S-duality.Comment: 23 pages, LaTeX; minor changes, version to be published in Nucl.
Phys.
Hologrphy and holographic dark energy model
The holographic principle is used to discuss the holographic dark energy
model. We find that the Bekenstein-Hawking entropy bound is far from saturation
under certain conditions. A more general constraint on the parameter of the
holographic dark energy model is also derived.Comment: no figures, use revtex, v2: use iop style, some typos corrected and
references updated, will appear in CQ
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