809 research outputs found
Self-Dual Chern-Simons Solitons in (2+1)-Dimensional Einstein Gravity
We consider here a generalization of the Abelian Higgs model in curved space,
by adding a Chern--Simons term. The static equations are self-dual provided we
choose a suitable potential. The solutions give a self-dual
Maxwell--Chern--Simons soliton that possesses a mass and a spin
Topology from the Simulated Sloan Digital Sky Survey
We measure the topology (genus curve) of the galaxy distribution in a mock
redshift catalog designed to resemble the upcoming Sloan Digital Sky Survey
(SDSS). The catalog, drawn from a large N-body simulation of a Lambda-CDM cos-
mological model, mimics the anticipated spectroscopic selection procedures of
the SDSS in some detail. Sky maps, redshift slices, and 3-D contour maps of the
mock survey reveal a rich and complex structure, including networks of voids
and superclusters that resemble the patterns seen in the CfA redshift survey
and the Las Campanas Redshift Survey (LCRS). The 3-D genus curve can be
measured from the simulated catalog with superb precision; this curve has the
general shape predicted for Gaussian, random phase initial conditions, but the
error bars are small enough to demonstrate with high significance the subtle
departures from this shape caused by non-linear gravitational evolution. These
distortions have the form predicted by Matsubara's (1994) perturbative anal-
ysis, but they are much smaller in amplitude. We also measure the 3-D genus
curve of the radial peculiar velocity field measured by applying distance-
indicator relations (with realistic errors) to the mock catalog. This genus
curve is consistent with the Gaussian random phase prediction, though it is of
relatively low precision because of the large smoothing length required to
overcome noise in the measured velocity field. Finally, we measure the 2-D
topology in redshift slices, similar to early slices from the SDSS and to
slices already observed in the LCRS. The genus curves of these slices are
consistent with the observed genus curves of the LCRS, providing further
evidence in favor of the inflationary CDM model with Omega_M~0.4. The catalog
is publicly available at http://www.astronomy.ohio-state.edu/~dhw/sdss.html.Comment: ASTeX 4.0 Preprint Style, 5 GIF figures (Figs 1, 2, 3a, 3b, 6; see
http://cfa-www.harvard.edu/~wcolley/SDSS_Top/ for PostScript versions), 7
PostScript figures. Figure 5 and Table 1 have minor corrections since
publicatio
Catalog of selected heavy duty transport energy management models
A catalog of energy management models for heavy duty transport systems powered by diesel engines is presented. The catalog results from a literature survey, supplemented by telephone interviews and mailed questionnaires to discover the major computer models currently used in the transportation industry in the following categories: heavy duty transport systems, which consist of highway (vehicle simulation), marine (ship simulation), rail (locomotive simulation), and pipeline (pumping station simulation); and heavy duty diesel engines, which involve models that match the intake/exhaust system to the engine, fuel efficiency, emissions, combustion chamber shape, fuel injection system, heat transfer, intake/exhaust system, operating performance, and waste heat utilization devices, i.e., turbocharger, bottoming cycle
(2+1)-Gravity Solutions with Spinning Particles
We derive, in 2+1 dimensions, classical solutions for metric and motion of
two or more spinning particles, in the conformal Coulomb gauge introduced
previously. The solutions are exact in the -body static case, and are
perturbative in the particles' velocities in the dynamic two-body case. A
natural boundary for the existence of our gauge choice is provided by some
``CTC horizons'' encircling the particles, within which closed timelike curves
occur.Comment: 30 pages, LaTeX, no figure
Gott time machines in the Anti-de Sitter space
In 1991 Gott presented a solution of Einstein's field equations in 2+1
dimensions with that contained closed timelike curves (CTC's).
This solution was remarkable because at first it did not seem to be unphysical
in any other respect. Later, however, it was shown that Gott's solution is
tachyonic in a certain sense. Here the case is discussed. We show
that it is possible to construct CTC's also in this case, in a way analogous to
that used by Gott. We also show that this construction still is tachyonic.
means that we are dealing with Anti-de Sitter space, and since
the CTC-construction necessitates some understanding of its structure, a few
pages are devoted to this subject.Comment: 11 page
Quantization of Point Particles in 2+1 Dimensional Gravity and Space-Time Discreteness
By investigating the canonical commutation rules for gravitating quantized
particles in a 2+1 dimensional world it is found that these particles live on a
space-time lattice. The space-time lattice points can be characterized by three
integers. Various representations are possible, the details depending on the
topology chosen for energy-momentum space. We find that an
topology yields a physically most interesting lattice within which first
quantization of Dirac particles is possible. An topology also gives a
lattice, but does not allow first quantized particles.Comment: 23 pages Plain TeX, 3 Figure
Vortices in Bogomol'nyi Limit of Einstein Maxwell Higgs Theory with or without External Sources
The Abelian Higgs model with or without external particles is considered in
curved space. Using the dual transformation, we rewrite the model in terms of
dual gauge fields and derive the Bogomol'nyi-type bound. We examine
cylindrically symmetric solutions to Einstein equations and the first-order
Bogomol'nyi equations, and find vortex solutions and vortex-particle composites
which lie on the spatial manifold with global geometry described by a cylinder
asymptotically or a two sphere in addition to the well-known cone.Comment: LaTeX, 23 pages, 10 LaTeX figures included, KHTP-93-05, SNUTP-93-100,
DPNU-93-46. (A note and several references added
Cumulants as non-Gaussian qualifiers
We discuss the requirements of good statistics for quantifying
non-Gaussianity in the Cosmic Microwave Background. The importance of
rotational invariance and statistical independence is stressed, but we show
that these are sometimes incompatible. It is shown that the first of these
requirements prefers a real space (or wavelet) formulation, whereas the latter
favours quantities defined in Fourier space. Bearing this in mind we decide to
be eclectic and define two new sets of statistics to quantify the level of
non-Gaussianity. Both sets make use of the concept of cumulants of a
distribution. However, one set is defined in real space, with reference to the
wavelet transform, whereas the other is defined in Fourier space. We derive a
series of properties concerning these statistics for a Gaussian random field
and show how one can relate these quantities to the higher order moments of
temperature maps. Although our frameworks lead to an infinite hierarchy of
quantities we show how cosmic variance and experimental constraints give a
natural truncation of this hierarchy. We then focus on the real space
statistics and analyse the non-Gaussian signal generated by points sources
obscured by large scale Gaussian fluctuations. We conclude by discussing the
practical implementations of these techniques
Two Dimensional Topology of Large Scale Structure in the Las Campanas Redshift Survey
We have measured the topology (genus) of the density distribution of
large-scale structure observed in the Las Campanas Redshift Survey (LCRS). The
LCRS is complete to magnitude 17.5, and contains nearly 24000 galaxies with
median redshift of 30000 km/s. The large volume and large number of galaxies
allows sampling of nearly 100 independent structures with which to compute the
genus topology, a vast improvement over previous studies. We find that the
genus is consistent with a random-phase Gaussian distribution of initial
density fluctuations, as would be produced naturally in inflationary models.
When we combine these results with the genus measurements of the COBE microwave
background fluctuations, we find that two orthogonal projections of the
three-dimensional distribution of initial density fluctuations are consistent
with Gaussian random-phase behavior, in agreement with standard inflationary
models. Particular attention is given to statistical significance of the genus
test.Comment: AASTeX, v4, preprint, 11 pages including 2 PS figure
A Self-Consistent Vacuum for Misner Space and the Chronology Protection Conjecture
In this paper we find a self-consistent vacuum for Misner space. For this
"adapted" Rindler vacuum the renormalized stress-energy tensor is zero
throughout the Misner space. A point-like particle detector traveling on a
timelike geodesic in a Misner space with this vacuum detects nothing. Misner
space with this vacuum thus creates no problems for time travel in and of
itself but a time traveler may pose a danger to himself and to the spacetime.Comment: 5 pages, received September 5, 1997, with a note added November 24,
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