8,836 research outputs found
Limit laws for k-coverage of paths by a Markov-Poisson-Boolean model
Let P := {X_i,i >= 1} be a stationary Poisson point process in R^d, {C_i,i >=
1} be a sequence of i.i.d. random sets in R^d, and {Y_i^t; t \geq 0, i >= 1} be
i.i.d. {0,1}-valued continuous time stationary Markov chains. We define the
Markov-Poisson-Boolean model C_t := {Y_i^t(X_i + C_i), i >= 1}. C_t represents
the coverage process at time t. We first obtain limit laws for k-coverage of an
area at an arbitrary instant. We then obtain the limit laws for the k-coverage
seen by a particle as it moves along a one-dimensional path.Comment: 1 figure. 24 Pages. Accepted at Stochastic Models. Theorems 6 and 7
corrected. Theorem 9 and Appendix adde
Workshop on gravitational waves
In this article we summarise the proceedings of the Workshop on Gravitational
Waves held during ICGC-95. In the first part we present the discussions on 3PN
calculations (L. Blanchet, P. Jaranowski), black hole perturbation theory (M.
Sasaki, J. Pullin), numerical relativity (E. Seidel), data analysis (B.S.
Sathyaprakash), detection of gravitational waves from pulsars (S. Dhurandhar),
and the limit on rotation of relativistic stars (J. Friedman). In the second
part we briefly discuss the contributed papers which were mainly on detectors
and detection techniques of gravitational waves.Comment: 18 pages, kluwer.sty, no figure
Variations in the Cyclotron Resonant Scattering Features during 2011 outburst of 4U 0115+63
We study the variations in the Cyclotron Resonant Scattering Feature (CRSF)
during 2011 outburst of the high mass X-ray binary 4U 0115+63 using
observations performed with Suzaku, RXTE, Swift and INTEGRAL satellites. The
wide-band spectral data with low energy coverage allowed us to characterize the
broadband continuum and detect the CRSFs. We find that the broadband continuum
is adequately described by a combination of a low temperature (kT ~ 0.8 keV)
blackbody and a power-law with high energy cutoff (Ecut ~ 5.4 keV) without the
need for a broad Gaussian at ~ 10 keV as used in some earlier studies. Though
winds from the companion can affect the emission from the neutron star at low
energies (< 3 keV), the blackbody component shows a significant presence in our
continuum model. We report evidence for the possible presence of two
independent sets of CRSFs with fundamentals at ~ 11 keV and ~ 15 keV. These two
sets of CRSFs could arise from spatially distinct emitting regions. We also
find evidence for variations in the line equivalent widths, with the 11 keV
CRSF weakening and the 15 keV line strengthening with decreasing luminosity.
Finally, we propose that the reason for the earlier observed anti-correlation
of line energy with luminosity could be due to modelling of these two
independent line sets (~ 11 keV and ~ 15 keV) as a single CRSF.Comment: 12 pages, 8 figures (4 in colour), 6 tables. Accepted for publication
in MNRAS. Typos corrected, Figure 8 changed and some changes to draf
The Frenet Serret Description of Gyroscopic Precession
The phenomenon of gyroscopic precession is studied within the framework of
Frenet-Serret formalism adapted to quasi-Killing trajectories. Its relation to
the congruence vorticity is highlighted with particular reference to the
irrotational congruence admitted by the stationary, axisymmetric spacetime.
General precession formulae are obtained for circular orbits with arbitrary
constant angular speeds. By successive reduction, different types of
precessions are derived for the Kerr - Schwarzschild - Minkowski spacetime
family. The phenomenon is studied in the case of other interesting spacetimes,
such as the De Sitter and G\"{o}del universes as well as the general
stationary, cylindrical, vacuum spacetimes.Comment: 37 pages, Paper in Late
First law of black hole mechanics in Einstein-Maxwell and Einstein-Yang-Mills theories
The first law of black hole mechanics is derived from the Einstein-Maxwell
(EM) Lagrangian by comparing two infinitesimally nearby stationary black holes.
With similar arguments, the first law of black hole mechanics in
Einstein-Yang-Mills (EYM) theory is also derived.Comment: Modified version, major changes made in the introduction. 14 pages,
no figur
Entropy of Constant Curvature Black Holes in General Relativity
We consider the thermodynamic properties of the constant curvature black hole
solution recently found by Banados. We show that it is possible to compute the
entropy and the quasilocal thermodynamics of the spacetime using the
Einstein-Hilbert action of General Relativity. The constant curvature black
hole has some unusual properties which have not been seen in other black hole
spacetimes. The entropy of the black hole is not associated with the event
horizon; rather it is associated with the region between the event horizon and
the observer. Further, surfaces of constant internal energy are not isotherms
so the first law of thermodynamics exists only in an integral form. These
properties arise from the unusual topology of the Euclidean black hole
instanton.Comment: 4 pages LaTeX2e (RevTeX), 2 PostScript figures. Small corrections in
the text and the reference
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