8,787 research outputs found
Data catalog series for space science and applications flight missions. Volume 3A: Descriptions of low- and medium-altitude scientific spacecraft and investigations
Earth orbits spacecraft whose apogees are well below geostationary altitude and whose primary purpose is to conduct investigations in the near-Earth environment are considered
Higher-dimensional resolution of dilatonic black hole singularities
We show that the four-dimensional extreme dilaton black hole with dilaton
coupling constant can be interpreted as a {\it completely
non-singular}, non-dilatonic, black -brane in dimensions provided
that is {\it odd}. Similar results are obtained for multi-black holes and
dilatonic extended objects in higher spacetime dimensions. The non-singular
black -brane solutions include the self-dual three brane of ten-dimensional
N=2B supergravity and a multi-fivebrane solution of eleven-dimensional
supergravity. In the case of a supersymmetric non-dilatonic -brane solution
of a supergravity theory, we show that it saturates a bound on the energy per
unit -volume.Comment: 27 pages, R/94/28, UCSBTH-94-35 (Comments added to the discussion
section
Growth of aerobic and anaerobic bacteria in agar subjected to freezing and diurnal freezing and thawing
Aerobic and anaerobic bacteria growth in agar after freezing and diurnal freezing and thawin
Black Holes with Multiple Charges and the Correspondence Principle
We consider the entropy of near extremal black holes with multiple charges in
the context of the recently proposed correspondence principle of Horowitz and
Polchinski, including black holes with two, three and four Ramond-Ramond
charges. We find that at the matching point the black hole entropy can be
accounted for by massless open strings ending on the D-branes for all cases
except a black hole with four Ramond-Ramond charges, in which case a possible
resolution in terms of brane-antibrane excitations is considered.Comment: 26 pages, harvmac, minor correction
Topology, Quantum Gravity and Particle Physics
It is argued that quantum gravity has an interpretation as a topological
field theory provided a certain constraint from the path intergral measure is
respected. The constraint forces us to couple gauge and matter fields to
gravity for space - time dimensions different from 3. We then discuss possible
models which may be relevant to our universe.Comment: 18 pages, LaTeX. Replaced version corrects typos and has additional
reference
Exact Supersymmetric Massive and Massless White Holes
We study special points in the moduli space of vacua at which supersymmetric
electric solutions of the heterotic string theory become massless. We
concentrate on configurations for which supersymmetric non-renormalization
theorem is valid. Those are ten-dimensional supersymmetric string waves and
generalized fundamental strings with SO(8) holonomy group. From these we find
the four dimensional spherically symmetric configurations which saturate the
BPS bound, in particular near the points of the vanishing ADM mass. The
non-trivial massless supersymmetric states in this class exist only in the
presence of non-Abelian vector fields.We also find a new class of
supersymmetric massive solutions, closely related to the massless ones. A
distinctive property of all these objects, either massless or massive, is the
existence of gravitational repulsion. They reflect all particles with
nonvanishing mass and/or angular momentum, and therefore they can be called
white holes (repulsons), in contrast to black holes which tend to absorb
particles of all kinds. If such objects can exist, we will have the first
realization of the universal gravitational force which repels all particles
with the strength proportional to their mass and therefore can be associated
with antigravity.Comment: 18 pages, minor corrections, version to be published in Phys.Rev.
An Equivalence Between Momentum and Charge in String Theory
It is shown that for a translationally invariant solution to string theory,
spacetime duality interchanges the momentum in the symmetry direction and the
axion charge per unit length. As one application, we show explicitly that
charged black strings are equivalent to boosted (uncharged) black strings. The
extremal black strings (which correspond to the field outside of a fundamental
macroscopic string) are equivalent to plane fronted waves describing strings
moving at the speed of light.Comment: 10 page
When Black Holes Meet Kaluza-Klein Bubbles
We explore the physical consequences of a recently discovered class of exact
solutions to five dimensional Kaluza-Klein theory. We find a number of
surprising features including: (1) In the presence of a Kaluza-Klein bubble,
there are arbitrarily large black holes with topology S^3. (2) In the presence
of a black hole or a black string, there are expanding bubbles (with de Sitter
geometry) which never reach null infinity. (3) A bubble can hold two black
holes of arbitrary size in static equilibrium. In particular, two large black
holes can be close together without merging to form a single black hole.Comment: 23 pages, 5 figures, v2: few comments on stability modifie
Extremal black holes as exact string solutions
We show that the leading order solution describing an extremal electrically
charged black hole in string theory is, in fact, an exact solution to all
orders in \a' when interpreted in a Kaluza-Klein fashion. This follows from
the observation that it can be obtained via dimensional reduction from a five
dimensional background which is proved to be an exact string solution.Comment: 13 pages, harvmac, Imperial/TP/93-94/51, UCSBTH-94-24 (references
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