14,337 research outputs found
The CWKB approach to non-reflecting potential and cosmological implications
We discuss the method of calculating the reflection coefficient using complex
trajectory WKB (CWKB) approximation. This enables us to give an interpretation
of non-reflecting nature of the potential under certain conditions and clarify
some points, reported incorrectly elsewhere [vs:ejp] for the potential
. We show that the repeated reflectios between the
turning points are essential, which most authors overlooked, in obtaining the
non-reflecting c ondition. We find that the considered repeated reflection
paths are in conformity with Bogolubov transformation technique. We discuss the
implications of the results when applied to the particle production scenario,
considering as a time variable and also stress the cosmological
implications of the result with reference to radiation domonated and de Sitter
spacetime.Comment: 9 pages, late
The CWKB Method of Particle Production in Periodic Potential
In this work we study the particle production in time dependent periodic
potential using the method of complex time WKB (CWKB) approximation. In the
inflationary cosmology at the end of inflationary stage, the potential becomes
time dependent as well as periodic. Reheating occurs due to particle production
by the oscillating inflaton field. Using CWKB we obtain almost identical
results on catastrophic particle production as obtained by others.Comment: 17 pages, latex, 2 figure
The Complex Time WKB Approximation And Particle Production
The complex time WKB (CWKB) approximation has been an effective technique to
understand particle production in curved as well as in flat spacetime. Earlier
we obtained the standard results on particle production in time dependent gauge
in various curved spacetime. In the present work we generalize the technique of
CWKB to the equivalent problems in space dependent gauge. Using CWKB, we first
obtain the gauge invariant result for particle production in Minkowski
spacetime in strong electric field. We then carry out particle production in
de-Sitter spacetime in space dependent gauge and obtain the same result that we
obtained earlier in time dependent gauge. The results obtained for de-Sitter
spacetime has a obvious extension to particle production in black hole
spacetime. It is found that the origin of Planckian spectrum is due to repeated
reflections between the turning points. As mentioned earlier, it is now
explicitly shown that particle production is accompanied by rotation of
currents.Comment: 12 pages, Revte
Detector calibration of the Indian cosmic ray experiment (IONS) in Space-Shuttle Spacelab-13
In the Indian cosmic ray experiment (IONS) in Spacelab-3 the intention is to study nuclei up to iron in low energy cosmic rays, using CR-39 (DOP) detectors. CR-39 (DOP) was exposed to He4, C12, O16, Ne20, Si28, Ar40, Cr52 and Fe56 accelerated beams from various accelerator facilities available around the world. Different beam energies and exposure angles were used. From these exposures, the charge resolution and energy resolution for the detector in the region of interest were studied. The effect of pre-annealing and depth on the response of our detector was studied. For isotopic resolution, exposed the detector samples were exposed to Ne2O and Ne22 accelerated beams. Samples of CR-39 (DOP) exposed to different accelerated heavy ions were kept in the detector module to take into account the effect of ambient conditions on detector response during the flight
Relative abundances of sub-iron to iron nuclei in low energy (50-250 MeV/N) cosmic rays as observed in the Skylab experiment
A Lexan polycarbonate detector exposed on the exterior of Skylab-3 for 73 days during a solar quiet period was used to study the relative abundances of calcium to nickel ions in low energy cosmic rays of 50 to 250 MeV/N. The method of charge identification is based on the measurement of conelength (L) and residual range (R) of these particles in various Lexan sheets. Since more than one cone (sometimes as many as five) is observed and is measured, the charge accuracy becomes precise and accurate. The ratio of (calcium to manganese) to (iron and cobalt) obtained at three energy intervals of 50 to 80, 80 to 150, 150 to 250 and 50 to 250 MeV/N are 7.6 plus or minus 3.8, 2.7 plus or minus 0.8, 1.4 plus or minus 0.6 and 3.3 plus or minus 0.7 respectively. These data thus indicate a large increase of this ratio with decreasing energy. The origin of this strong energy dependence is not understood at present
Inseparability inequalities for higher-order moments for bipartite systems
There are several examples of bipartite entangled states of continuous
variables for which the existing criteria for entanglement using the
inequalities involving the second order moments are insufficient. We derive new
inequalities involving higher order correlation, for testing entanglement in
non-Gaussian states. In this context we study an example of a non-Gaussian
state, which is a bipartite entangled state of the form .
Our results open up an avenue to search for new inequalities to test
entanglement in non-Gaussian states.Comment: 7 pages, Submitte
Periodic Orbits in Polygonal Billiards
We review some properties of periodic orbit families in polygonal billiards
and discuss in particular a sum rule that they obey. In addition, we provide
algorithms to determine periodic orbit families and present numerical results
that shed new light on the proliferation law and its variation with the genus
of the invariant surface. Finally, we deal with correlations in the length
spectrum and find that long orbits display Poisson fluctuations.Comment: 30 pages (Latex) including 11 figure
Quantum Gravity Equation In Schroedinger Form In Minisuperspace Description
We start from classical Hamiltonian constraint of general relativity to
obtain the Einstein-Hamiltonian-Jacobi equation. We obtain a time parameter
prescription demanding that geometry itself determines the time, not the matter
field, such that the time so defined being equivalent to the time that enters
into the Schroedinger equation. Without any reference to the Wheeler-DeWitt
equation and without invoking the expansion of exponent in WKB wavefunction in
powers of Planck mass, we obtain an equation for quantum gravity in
Schroedinger form containing time. We restrict ourselves to a minisuperspace
description. Unlike matter field equation our equation is equivalent to the
Wheeler-DeWitt equation in the sense that our solutions reproduce also the
wavefunction of the Wheeler-DeWitt equation provided one evaluates the
normalization constant according to the wormhole dominance proposal recently
proposed by us.Comment: 11 Pages, ReVTeX, no figur
Time in Quantum Gravity
The Wheeler-DeWitt equation in quantum gravity is timeless in character. In
order to discuss quantum to classical transition of the universe, one uses a
time prescription in quantum gravity to obtain a time contained description
starting from Wheeler-DeWitt equation and WKB ansatz for the WD wavefunction.
The approach has some drawbacks. In this work, we obtain the time-contained
Schroedinger-Wheeler-DeWitt equation without using the WD equation and the WKB
ansatz for the wavefunction. We further show that a Gaussian ansatz for SWD
wavefunction is consistent with the Hartle-Hawking or wormhole dominance
proposal boundary condition. We thus find an answer to the small scale boundary
conditions.Comment: 12 Pages, LaTeX, no figur
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