2,044 research outputs found
Possible observation of energy level quantization in an intrinsic Josephson junction
Energy level quantization (ELQ) is studied to clarify the macroscopic quantum
dynamics of the d-wave Josephson junction (JJ). The influences of the nodal
quasiparticles of d-wave superconductivity on the damping effect are
numerically evaluated on the basis of a phenomenological model. The
calculation, based on realistic parameters for a Bi2Sr2CaCu2O8+d (Bi2212)
intrinsic JJ, shows that the observation of ELQ is possible when the sweep rate
of the bias current exceeds 10 A/sec. High-sweep- rate measurements (121A/sec)
performed on a Bi2212 intrinsic JJ result in the appearance of multiple peaks
in the switching current distribution suggesting the realization of ELQ in the
d-wave JJ.Comment: 5 pages, 3 figure
Gravitational radiation from infall into a black hole: Regularization of the Teukolsky equation
The Teukolsky equation has long been known to lead to divergent integrals
when it is used to calculate the gravitational radiation emitted when a test
mass falls into a black hole from infinity. Two methods have been used in the
past to remove those divergent integrals. In the first, integrations by parts
are carried out, and the infinite boundary terms are simply discarded. In the
second, the Teukolsky equation is transformed into another equation which does
not lead to divergent integrals. The purpose of this paper is to show that
there is nothing intrinsically wrong with the Teukolsky equation when dealing
with non-compact source terms, and that the divergent integrals result simply
from an incorrect choice of Green's function. In this paper, regularization of
the Teukolsky equation is carried out in an entirely natural way which does not
involve modifying the equation.Comment: ReVTeX, 23 page
Temperature Variation in the Cluster of Galaxies Abell 115 Studied with ASCA
Abell 115 exhibits two distinct peaks in the surface brightness distribution.
ASCA observation shows a significant temperature variation in this cluster,
confirmed by a hardness ratio analysis and spectral fits. A linking region
between main and sub clusters shows a high temperature compared with other
regions. Two possibilities are examined as the cause of the temperature
variation: cooling flows in the main cluster and a shock heating due to the
collision of the subcluster into the main system. Spectral fits with cooling
flow models to the main-cluster data show a mass-deposition rate less than 419
solar-mass/yr. Temperatures in the main cluster, the linking region, and the
subcluster are estimated by correcting for the effects of X-ray telescope
response as 4.9 (+0.7/-0.6), 11 (+12/-4), and 5.2 (+1.4/-1.0) keV,
respectively. The high temperature in the linking region implies that Abell 115
is indeed a merger system, with possible contribution from cooling flows on the
temperature structure.Comment: 23 pages, including 7 Postscript figures, accepted for publication in
Ap
Gravitational Waves from a Particle Orbiting Around a Rotating Black Holes: Post-Newtonian Expansion
Using the Teukolsky and Sasaki-Nakamura equations for the gravitational
perturbation of the Kerr spacetime, we calculate the post-Newtonian expansion
of the energy and angular momentum luminosities of gravitational waves from a
test particle orbiting around a rotating black hole up through
order beyond the quadrupole formula. We apply a method recently developed by
Sasaki to the case of a rotating black hole. We take into account a small
inclination of the orbital plane to the lowest order of the Carter constant.
The result to P^{3/2}N} order is in agreement with a similar calculation by
Poisson as well as with the standard post-Newtonian calculation by Kidder et
al. Using our result, we calculate the integrated phase of gravitational waves
from a neutron star-neutron star binary and a black hole-neutron star binary
during their inspiral stage. We find that, in both cases, spin-dependent terms
in the PN and PN corrections are important to construct effective
template waveforms which will be used for future laser-interferometric
gravitational wave detectors.Comment: phyzzx 41 page
Various features of quasiequilibrium sequences of binary neutron stars in general relativity
Quasiequilibrium sequences of binary neutron stars are numerically calculated
in the framework of the Isenberg-Wilson-Mathews (IWM) approximation of general
relativity. The results are presented for both rotation states of synchronized
spins and irrotational motion, the latter being considered as the realistic one
for binary neutron stars just prior to the merger. We assume a polytropic
equation of state and compute several evolutionary sequences of binary systems
composed of different-mass stars as well as identical-mass stars with adiabatic
indices gamma=2.5, 2.25, 2, and 1.8. From our results, we propose as a
conjecture that if the turning point of binding energy (and total angular
momentum) locating the innermost stable circular orbit (ISCO) is found in
Newtonian gravity for some value of the adiabatic index gamma_0, that of the
ADM mass (and total angular momentum) should exist in the IWM approximation of
general relativity for the same value of the adiabatic index.Comment: Text improved, some figures changed or deleted, new table, 38 pages,
31 figures, accepted for publication in Phys. Rev.
Re-colonizing spaces of memorializing: the case of the Chattri Indian Memorial, UK
This article inspects the ways that spaces of war memorialization are organized and reorganized through official and unofficial meaning-making activities. It aims to contribute to the discussion of the âvalueâ of memorializing by examining a multifaceted space of remembrance and commemoration: the Chattri Indian Memorial built near Brighton, UK. The article brings postcolonial perspectives to explore how memorializing has been organized here, focusing on the activities of once-colonized people and the affective, embodied aspects of organizing practices. Built in 1921 to honour Indian soldiers who fought in WWI, the Chattri evolved from a colonial instrument to symbol and space for ethnic-Indian group activities. The study employed historical, visual and ethnographic methods to study the tangible monument and the changing nature of the memorializing activities carried out around the monument. Memorializing is conceptualized within three inter-related processes: colonizing, de-colonizing and re-colonizing to examine how forms and practices of memorialization constitute a values-laden organizing system
Measuring black-hole parameters and testing general relativity using gravitational-wave data from space-based interferometers
Among the expected sources of gravitational waves for the Laser
Interferometer Space Antenna (LISA) is the capture of solar-mass compact stars
by massive black holes residing in galactic centers. We construct a simple
model for such a capture, in which the compact star moves freely on a circular
orbit in the equatorial plane of the massive black hole. We consider the
gravitational waves emitted during the late stages of orbital evolution,
shortly before the orbiting mass reaches the innermost stable circular orbit.
We construct a simple model for the gravitational-wave signal, in which the
phasing of the waves plays the dominant role. The signal's behavior depends on
a number of parameters, including , the mass of the orbiting star, ,
the mass of the central black hole, and , the black hole's angular momentum.
We calculate, using our simplified model, and in the limit of large
signal-to-noise ratio, the accuracy with which these quantities can be
estimated during a gravitational-wave measurement. Our simplified model also
suggests a method for experimentally testing the strong-field predictions of
general relativity.Comment: ReVTeX, 16 pages, 5 postscript figure
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