5,463 research outputs found
On Weighted Generalized Residual Information Measure
In this paper, we have proposed the concept of weighted generalized residual entropy of order α and type β, and have shown that the proposed measure characterizes the distribution function uniquely
Tunable nonlinearity in atomic response to a bichromatic field
Atomic response to a probe beam can be tailored, by creating coherences
between atomic levels with help of another beam. Changing parameters of the
control beam will change the nature of coherences and hence the nature of
atomic response as well. Such change can depend upon intensity of both probe
and control beams, in a nonlinear fashion. We present a situation where this
nonlinearity in dependence can be precisely controlled, as to obtain different
variations as desired. We also present a detailed analysis of how this
nonlinear dependency arises and show that this is an interesting effect of
several Coherent Population Trap(CPT) states that exist and a competition among
them to trap atomic population in them.Comment: 16 pages and 6 figure
Hybrid Stars
Recently there have been important developments in the determination of
neutron star masses which put severe constraints on the composition and
equation of state (EOS) of the neutron star matter. Here we study the effect of
quark and nuclear matter mixed phase on mass radius relationship of neutron
stars employing recent models from two classes of EOS's and discuss their
implications.Comment: 3 pages LaTeX including 2 figures, macros included, Talk presented at
the IX International Symposium on Particles, Strings and Cosmology
(PASCOS'03), TIFR, Mumbai, India, January 3-8,2003. To appear in their
proceeding
Monodromy Matrix in the PP-Wave Limit
We construct the monodromy matrix for a class of gauged WZWN models in the
plane wave limit and discuss various properties of such systems.Comment: 16 page
The response of laser interferometers to a gravitational wave
Laser interferometer detectors are now widely used in an attempt to detect
gravitational waves (gw). The interaction of the gw with the light circulating
in the interferometer is usually explained in terms of the motion of the "free"
mirrors that form the interferometer arms. It is however instructive to show
that the same result can be obtained by simply calculating the propagation of
an electromagnetic plane wave between "free mirrors" in the curved space-time
induced by the gw. One finds that the plane wave acquires frequency modulation
sidebands at the gw frequency, as would be expected from the absorption and
emission of gravitons from and to the gw. Such sidebands are completely
equivalent to the time-dependent phase shift imposed on the plane wave, that
follows from the conventional calculation
Dynamical evolution of the Universe in the quark-hadron phase transition and possible nugget formation
We study the dynamics of first-order phase transition in the early Universe
when it was old with quarks and gluons condensing into hadrons.
We look at how the Universe evolved through the phase transition in small as
well as large super cooling scenario, specifically exploring the formation of
quark nuggets and their possible survival. The nucleation of the hadron phase
introduces new distance scales in the Universe, which we estimate along with
the hadron fraction, temperature, nucleation time etc. It is of interest to
explore whether there is a relic signature of this transition in the form of
quark nuggets which might be identified with the recently observed dark objects
in our galactic halo and account for the Dark Matter in the Universe at
present.Comment: LaTeX file with four postscript figure
An evolved disk surrounding the massive main sequence star MWC 297?
We present the results of the interferometric observations of the
circumstellar disk surrounding MWC 297 in the continuum at 230 GHz (1.3 mm) and
in the (J=2-1) rotational transitions of CO,CO and CO
using the Submillimeter Array. At a distance of 250 pc, MWC 297 is one of the
closest, young massive stars (M 10 M) to us. Compact
continuum emission is detected towards MWC 297 from which we estimate a disk
mass (gas+dust) of 0.07 M and a disk radius of 80 AU. Our
result demonstrates that circumstellar disks can survive around massive stars
well into their main sequence phase even after they have become optically
visible. Complementing our observations with the data compiled from the
literature, we find the submm dust opacity index to be between 0.1 and
0.3. If the emission is optically thin, the low value of indicates the
presence of relatively large grains in the disk, possibly because of grain
growth. We do not detect any CO emission associated with the continuum source.
We argue that the CO emission from the disk is likely optically thin, in
which case, we derive an upper limit to the gas mass which implies significant
depletion of molecular gas in the disk. The mass of this disk and the
evolutionary trends observed are similar to those found for intermediate mass
Herbig Ae stars and low mass T Tauri stars.Comment: 4 pages, 3 Figures, accepted for publication in ApJ
Dark Energy density in models with Split Supersymmetry and degenerate vacua
In N=1 supergravity supersymmetric (SUSY) and non-supersymmetric Minkowski
vacua originating in the hidden sector can be degenerate. In the supersymmetric
phase in flat Minkowski space non-perturbative supersymmetry breakdown may take
place in the observable sector, inducing a non-zero and positive vacuum energy
density. Assuming that such a supersymmetric phase and the phase in which we
live are degenerate, we estimate the value of the cosmological constant. We
argue that the observed value of the dark energy density can be reproduced in
the Split-SUSY scenario of the supersymmetry breaking if the SUSY breaking
scale is of order of 10^{10} GeV.Comment: 20 pages, 1 figure, some minor changes to the text, references adde
B-type defects in Landau-Ginzburg models
We consider Landau-Ginzburg models with possibly different superpotentials
glued together along one-dimensional defect lines. Defects preserving B-type
supersymmetry can be represented by matrix factorisations of the difference of
the superpotentials. The composition of these defects and their action on
B-type boundary conditions is described in this framework. The cases of
Landau-Ginzburg models with superpotential W=X^d and W=X^d+Z^2 are analysed in
detail, and the results are compared to the CFT treatment of defects in N=2
superconformal minimal models to which these Landau-Ginzburg models flow in the
IR.Comment: 50 pages, 2 figure
Light-front Schwinger Model at Finite Temperature
We study the light-front Schwinger model at finite temperature following the
recent proposal in \cite{alves}. We show that the calculations are carried out
efficiently by working with the full propagator for the fermion, which also
avoids subtleties that arise with light-front regularizations. We demonstrate
this with the calculation of the zero temperature anomaly. We show that
temperature dependent corrections to the anomaly vanish, consistent with the
results from the calculations in the conventional quantization. The gauge
self-energy is seen to have the expected non-analytic behavior at finite
temperature, but does not quite coincide with the conventional results.
However, the two structures are exactly the same on-shell. We show that
temperature does not modify the bound state equations and that the fermion
condensate has the same behavior at finite temperature as that obtained in the
conventional quantization.Comment: 10 pages, one figure, version to be published in Phys. Rev.
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