7,957 research outputs found
Schwarzschild-de Sitter Spacetimes, McVittie Coordinates, and Trumpet Geometries
Trumpet geometries play an important role in numerical simulations of black
hole spacetimes, which are usually performed under the assumption of asymptotic
flatness. Our Universe is not asymptotically flat, however, which has motivated
numerical studies of black holes in asymptotically de Sitter spacetimes. We
derive analytical expressions for trumpet geometries in Schwarzschild-de Sitter
spacetimes by first generalizing the static maximal trumpet slicing of the
Schwarzschild spacetime to static constant mean curvature trumpet slicings of
Schwarzschild-de Sitter spacetimes. We then switch to a comoving isotropic
radial coordinate which results in a coordinate system analogous to McVittie
coordinates. At large distances from the black hole the resulting metric
asymptotes to a Friedmann-Lemaitre-Robertson-Walker metric with an
exponentially-expanding scale factor. While McVittie coordinates have another
asymptotically de Sitter end as the radial coordinate goes to zero, so that
they generalize the notion of a "wormhole" geometry, our new coordinates
approach a horizon-penetrating trumpet geometry in the same limit. Our
analytical expressions clarify the role of time-dependence, boundary conditions
and coordinate conditions for trumpet slices in a cosmological context, and
provide a useful test for black hole simulations in asymptotically de Sitter
spacetimes.Comment: 7 pages, 3 figures, added referenc
Approximate initial data for binary black holes
We construct approximate analytical solutions to the constraint equations of
general relativity for binary black holes of arbitrary mass ratio in
quasicircular orbit. We adopt the puncture method to solve the constraint
equations in the transverse-traceless decomposition and consider perturbations
of Schwarzschild black holes caused by boosts and the presence of a binary
companion. A superposition of these two perturbations then yields approximate,
but fully analytic binary black hole initial data that are accurate to first
order in the inverse of the binary separation and the square of the black
holes' momenta.Comment: 13 pages, 4 figures, added comparison to numerical calculations,
accepted to PR
Trumpet Slices in Kerr Spacetimes
We introduce a new time-independent family of analytical coordinate systems
for the Kerr spacetime representing rotating black holes. We also propose a
(2+1)+1 formalism for the characterization of trumpet geometries. Applying this
formalism to our new family of coordinate systems we identify, for the first
time, analytical and stationary trumpet slices for general rotating black
holes, even for charged black holes in the presence of a cosmological constant.
We present results for metric functions in this slicing and analyze the
geometry of the rotating trumpet surface.Comment: 5 pages, 2 figures; version published in PR
Finite-State Channel Models for Signal Transduction in Neural Systems
Information theory provides powerful tools for understanding communication
systems. This analysis can be applied to intercellular signal transduction,
which is a means of chemical communication among cells and microbes. We discuss
how to apply information-theoretic analysis to ligand-receptor systems, which
form the signal carrier and receiver in intercellular signal transduction
channels. We also discuss the applications of these results to neuroscience.Comment: Accepted for publication in 2016 IEEE International Conference on
Acoustics, Speech, and Signal Processing, Shanghai, Chin
Understanding the Interaction Between Cotton Ginning and Rural Economics in the Mid-South Under A Changing Cotton Environment
This study estimates economic impact of ginning on Mid-South states applying input-output analysis to gin cost data. Results indicated that cotton ginning activity in the Mid-South generated over 438 million in total effects with a multiplier of 2.39.cotton, cotton ginning, economic impact, multiplier, Mid-South, input-output, Agribusiness, Community/Rural/Urban Development, R15,
ECONOMICS OF ALTERNATIVE BEEF CATTLE GENOTYPE AND MANAGEMENT/MARKETING SYSTEMS
Livestock Production/Industries,
Trumpet slices of the Schwarzschild-Tangherlini spacetime
We study families of time-independent maximal and 1+log foliations of the
Schwarzschild-Tangherlini spacetime, the spherically-symmetric vacuum black
hole solution in D spacetime dimensions, for D >= 4. We identify special
members of these families for which the spatial slices display a trumpet
geometry. Using a generalization of the 1+log slicing condition that is
parametrized by a constant n we recover the results of Nakao, Abe, Yoshino and
Shibata in the limit of maximal slicing. We also construct a numerical code
that evolves the BSSN equations for D=5 in spherical symmetry using
moving-puncture coordinates, and demonstrate that these simulations settle down
to the trumpet solutions.Comment: 11 pages, 6 figures, submitted to PR
Distribution, movements, and habitat use of small striped bass (Morone saxatilis) across multiple spatial scales
Distribution, movements, and habitat use of small (<46 cm,
juveniles and individuals of unknown maturity) striped bass (Morone saxatilis) were investigated with multiple
techniques and at multiple spatial scales (surveys and tag-recapture in the estuary and ocean, and telemetry in the estuary) over multiple years to determine the frequency and duration of use of non-natal estuaries. These unique comparisons suggest, at least in New Jersey, that smaller
individuals (<20 cm) may disperse from natal estuaries and arrive in non-natal estuaries early in life and take up residence for several years. During this period of estuarine residence, individuals spend all seasons primarily in the low salinity portions of the estuary. At larger sizes, they then leave these non-natal estuaries
to begin coastal migrations with those individuals from nurseries in natal estuaries. These composite observations
of frequency and duration of habitat use indicate that non-natal estuaries may provide important habitat for a portion of the striped bass population
Modeling Uncertainty in Large Natural Resource Allocation Problems
The productivity of the world's natural resources is critically dependent on a variety of highly uncertain factors, which obscure individual investors and governments that seek to make long-term, sometimes irreversible investments in their exploration and utilization. These dynamic considerations are poorly represented in disaggregated resource models, as incorporating uncertainty into large-dimensional problems presents a challenging computational task. This study introduces a novel numerical method to solve large-scale dynamic stochastic natural resource allocation problems that cannot be addressed by conventional methods. The method is illustrated with an application focusing on the allocation of global land resource use under stochastic crop yields due to adverse climate impacts and limits on further technological progress. For the same model parameters, the range of land conversion is considerably smaller for the dynamic stochastic model as compared to deterministic scenario analysis. The scenario analysis can thus significantly overstate the magnitude of expected land conversion under uncertain crop yields
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