1,313 research outputs found
Scattering of Several Multiply Charged Extremal D=5 Black Holes
The moduli space metric for an arbitrary number of extremal D=5 black holes
with arbitrary relatively supersymmetric charges is found.Comment: 12 pages, ReVTeX. Minor typos corrected, including an unimportant
sign for which the corresponding comment was removed. One reference adde
Efficiency of a Brownian information machine
A Brownian information machine extracts work from a heat bath through a
feedback process that exploits the information acquired in a measurement. For
the paradigmatic case of a particle trapped in a harmonic potential, we
determine how power and efficiency for two variants of such a machine operating
cyclically depend on the cycle time and the precision of the positional
measurements. Controlling only the center of the trap leads to a machine that
has zero efficiency at maximum power whereas additional optimal control of the
stiffness of the trap leads to an efficiency bounded between 1/2, which holds
for maximum power, and 1 reached even for finite cycle time in the limit of
perfect measurements.Comment: 9 pages, 2 figure
Plane waves with weak singularities
We study a class of time dependent solutions of the vacuum Einstein equations
which are plane waves with weak null singularities. This singularity is weak in
the sense that though the tidal forces diverge at the singularity, the rate of
divergence is such that the distortion suffered by a freely falling observer
remains finite. Among such weak singular plane waves there is a sub-class which
do not exhibit large back reaction in the presence of test scalar probes.
String propagation in these backgrounds is smooth and there is a natural way to
continue the metric beyond the singularity. This continued metric admits string
propagation without the string becoming infinitely excited. We construct a one
parameter family of smooth metrics which are at a finite distance in the space
of metrics from the extended metric and a well defined operator in the string
sigma model which resolves the singularity.Comment: 22 pages, Added references and clarifying comment
Dynamic changes of the extracellular matrix after acute tako-tsubo cardiomyopathy
Funding Tenovus Scotland. Grant number G13/10.Peer reviewedPublisher PD
Statistical Entropy of Nonextremal Four-Dimensional Black Holes and U-Duality
We identify the states in string theory which are responsible for the entropy
of near-extremal rotating four-dimensional black holes in supergravity.
For black holes far from extremality (with no rotation), the Bekenstein-Hawking
entropy is exactly matched by a mysterious duality invariant extension of the
formulas derived for near-extremal black holes states.Comment: 9 pages, harvma
Computing and data processing
The applications of computers and data processing to astronomy are discussed. Among the topics covered are the emerging national information infrastructure, workstations and supercomputers, supertelescopes, digital astronomy, astrophysics in a numerical laboratory, community software, archiving of ground-based observations, dynamical simulations of complex systems, plasma astrophysics, and the remote control of fourth dimension supercomputers
Black Hole Hair Removal: Non-linear Analysis
BMPV black holes in flat transverse space and in Taub-NUT space have
identical near horizon geometries but different microscopic degeneracies. It
has been proposed that this difference can be accounted for by different
contribution to the degeneracies of these black holes from hair modes, --
degrees of freedom living outside the horizon. In this paper we explicitly
construct the hair modes of these two black holes as finite bosonic and
fermionic deformations of the black hole solution satisfying the full
non-linear equations of motion of supergravity and preserving the supersymmetry
of the original solutions. Special care is taken to ensure that these solutions
do not have any curvature singularity at the future horizon when viewed as the
full ten dimensional geometry. We show that after removing the contribution due
to the hair degrees of freedom from the microscopic partition function, the
partition functions of the two black holes agree.Comment: 40 pages, LaTe
Statistical Origin of Black Hole Entropy in Matrix Theory
The statistical entropy of black holes in M-theory is considered. Assuming
Matrix theory is the discretized light-cone quantization of a theory with
eleven-dimensional Lorentz invariance, we map the counting problem onto the
original Gibbons-Hawking calculation of the thermodynamic entropy.Comment: 9 pages, harvmac, (v2 References added, typo fixed), (v3 Some
clarifying comments added.
Higher spin quasinormal modes and one-loop determinants in the BTZ black hole
We solve the wave equations of arbitrary integer spin fields in the BTZ black
hole background and obtain exact expressions for their quasinormal modes. We
show that these quasinormal modes precisely agree with the location of the
poles of the corresponding two point function in the dual conformal field
theory as predicted by the AdS/CFT correspondence. We then use these
quasinormal modes to construct the one-loop determinant of the higher spin
field in the thermal BTZ background. This is shown to agree with that obtained
from the corresponding heat kernel constructed recently by group theoretic
methods.Comment: 47 page
Climate variability modulates western US ozone air quality in spring via deep stratospheric intrusions
Evidence suggests deep stratospheric intrusions can elevate western US surface ozone to unhealthy levels during spring. These intrusions can be classified as ‘exceptional events’, which are not counted towards non-attainment determinations. Understanding the factors driving the year-to-year variability of these intrusions is thus relevant for effective implementation of the US ozone air quality standard. Here we use observations and model simulations to link these events to modes of climate variability. We show more frequent late spring stratospheric intrusions when the polar jet meanders towards the western United States, such as occurs following strong La Niña winters (Niño3.4<−1.0 °C). While El Niño leads to enhancements of upper tropospheric ozone, we find this influence does not reach surface air. Fewer and weaker intrusion events follow in the two springs after the 1991 volcanic eruption of Mt. Pinatubo. The linkage between La Niña and western US stratospheric intrusions can be exploited to provide a few months of lead time during which preparations could be made to deploy targeted measurements aimed at identifying these exceptional events
- …