21,927 research outputs found
Vacuum structure and effective potential at finite temperature: a variational approach
We compute the effective potential for theory with a squeezed
coherent state type of construct for the ground state. The method essentially
consists in optimising the basis at zero and finite temperatures. The gap
equation becomes identical to resumming the infinite series of daisy and super
daisy graphs while the effective potential includes multiloop effects and
agrees with that obtained through composite operator formalism at finite
temperature.Comment: 15 pages, Revtex, No figures, to appear in Jou. of Phys.G(Nucl. and
Part. Phys.
First principles calculation of polarization induced interfacial charges in GaN/AlN heterostructures
We propose a new method to calculate polarization induced interfacial charges
in semiconductor heterostructures using classical electrostatics applied to
real-space band diagrams from first principles calculations and apply it to
GaN/AlN heterostructures with ultrathin AlN layers (4-6 monolayers). We show
that the calculated electric fields and interfacial charges are independent of
the exchange-correlation functionals used (local-density approximation and
hybrid functionals). We also find the calculated interfacial charge of (6.8 +/-
0.4) x 10^13 cm-2 to be in excellent agreement with experiments and the value
of 6.58 x 10^13 cm-2 calculated from bulk polarization constants, validating
the use of bulk constants even for very thin films.Comment: 3 pages, 2 figures; submitted to Applied Physics Letter
Statistical Mechanics of DNA Rupture: Theory and Simulations
We study the effects of the shear force on the rupture mechanism on a double
stranded DNA. Motivated by recent experiments, we perform the atomistic
simulations with explicit solvent to obtain the distributions of extension in
hydrogen and covalent bonds below the rupture force. We obtain a significant
difference between the atomistic simulations and the existing results in the
iterature based on the coarse-grained models (theory and simulations). We
discuss the possible reasons and improve the coarse-grained model by
incorporating the consequences of semi-microscopic details of the nucleotides
in its description. The distributions obtained by the modified model
(simulations and theoretical) are qualitatively similar to the one obtained
using atomistic simulations.Comment: 18 pages, 9 figures. Accepted in J. Chem. Phys. (2013). arXiv admin
note: text overlap with arXiv:1104.305
Resolution of puzzles from the LSND, KARMEN, and MiniBooNE experiments
This work has attempted to reconcile puzzling neutrino oscillation results
from the LSND, KARMEN and MiniBooNE experiments. We show that the LSND evidence
for oscillations, its long-standing
disagreement with the results from KARMEN, and the anomalous event excess
observed by MiniBooNE in and data could all be
explained by the existence of a heavy sterile neutrino (). All these
results are found to be consistent with each other assuming that the is
created in neutral-current interactions and decays radiatively into a
photon and a light neutrino. Assuming the is produced through mixing
with , the combined analysis of the LSND and MiniBooNe excess events
suggests that the mass is in the range from 40 to 80 MeV, the mixing
strength is , and the lifetime is
s. Surprisingly, this LSND-MiniBooNE parameters
window is found to be unconstrained by the results from the most sensitive
experiments searching for heavy neutrino. We set new limits on
for the LSND-MiniBooNE favorable mass region from the precision measurements of
the Michel spectrum by the TWIST experiment. The results obtained provide a
strong motivation for a sensitive search for the in a near future
decay or neutrino experiments, which fit well in the existing/planned
experimental programs at CERN or FNAL. The question of whether the heavy
neutrino is Dirac or Majorana particle is briefly discussed.Comment: 24 pages, 28 figures, version to appear in PR
Vector meson masses in hot nuclear matter : the effect of quantum corrections
The medium modification of vector meson masses is studied taking into account
the quantum correction effects for the hot and dense hadronic matter. In the
framework of Quantum Hadrodynamics, the quantum corrections from the baryon and
scalar meson sectors were earlier computed using a nonperturbative variational
approach through a realignment of the ground state with baryon-antibaryon and
sigma meson condensates. The effect of such corrections was seen to lead to a
softer equation of state giving rise to a lower value for the compressibility
and, an increase in the in-medium baryonic masses than would be reached when
such quantum effects are not taken into account. These quantum corrections
arising from the scalar meson sector result in an increase in the masses of the
vector mesons in the hot and dense matter, as compared to the situation when
only the vacuum polarisation effects from the baryonic sector are taken into
account.Comment: 13 pages revtex file, 6 figure
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