19,272 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
Study of timing properties of single gap high-resistive bakelite RPC
The time resolution for several single gap (2 mm) prototype Resistive Plate
Chambers (RPC) made of high resistive (bulk resistivity ~ 10^10 - 10^12 ohm
cm), 2 mm thick matt finished bakelite paper laminates with silicone coating on
the inner surfaces, has been measured. The time resolution for all the modules
has been found to be ~ 2 ns at the plateau region.Comment: 5 figures, Presented in Frontier Detectors for Frontier Physics (11th
Pisa meeting on advanced detectors), La Biodala, Isola d'Elba, Italy, May
24-30, 200
Performances of silicone coated high resistive bakelite RPC
Performances of several single gap (gas gap 2 mm) prototype Resistive Plate
Chambers (RPC) made of high resistive ({\rho} \sim 1010 - 1012 {\Omega} cm)
bakelite, commercially available in India have been studied in recent times. To
make the inner electrode surfaces smooth, a thin coating of silicone has been
applied. An efficiency > 90% and time resolution \sim 2 ns (FWHM) have been
obtained for both the streamer and the avalanche mode. The induced charge
distributions of those silicone coated RPC are studied and the results are
presented. A numerical study on the effect of surface roughness of the
resistive electrodes on the electric field of the device has been carried out
using Garfield-neBEM code. A few results for a simplified model representing
surface roughness, measured using a surface profilometer for the bakelite
surfaces, have also been presented
Schroedinger Wheeler-DeWitt Equation In Multidimensional Cosmology
We study multidimensional cosmology to obtain the wavefunction of the
universe using wormhole dominance proposal. Using a prescription for time we
obtain the Schroedinger-Wheeler-DeWitt equation without any reference to WD
equation and WKB ansatz for WD wavefunction. It is found that the
Hartle-Hawking or wormhole-dominated boundary conditions serve as a seed for
inflation as well as for Gaussian type ansatz to Schroedinger-Wheeler-DeWitt
equation.Comment: 10 Pages, LaTeX, no figur
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
On bouncing solutions in non-local gravity
A non-local modified gravity model with an analytic function of the
d'Alembert operator is considered. This model has been recently proposed as a
possible way of resolving the singularities problem in cosmology. We present an
exact bouncing solution, which is simpler compared to the already known one in
this model in the sense it does not require an additional matter to satisfy all
the gravitational equations.Comment: 5 pages; v2: matching the jounral versio
Nonclassicality and decoherence of photon-subtracted squeezed states
We discuss nonclassical properties of single-photon subtracted squeezed
vacuum states in terms of the sub-Poissonian statistics and the negativity of
the Wigner function. We derive a compact expression for the Wigner function
from which we find the region of phase space where Wigner function is negative.
We find an upper bound on the squeezing parameter for the state to exhibit
sub-Poissonian statistics. We then study the effect of decoherence on the
single-photon subtracted squeezed states. We present results for two different
models of decoherence, viz. amplitude decay model and the phase diffusion
model. In each case we give analytical results for the time evolution of the
state. We discuss the loss of nonclassicality as a result of decoherence. We
show through the study of their phase-space properties how these states decay
to vacuum due to the decay of photons. We show that phase damping leads to very
slow decoherence than the photon-number decay.Comment: Figures are in GIF format separately, submitte
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