1,694 research outputs found
Slow-roll inflationary senario in the maximally extended background
During the inflationary epoch,geometry of the universe may be described by
quasi-de Sitter space. On the other hand,maximally extended de Sitter metric in
the comoving coordinates accords with a special FLRW model with positive
spatial curvature,so in this article we focus on the positively curved
inflationary paradigm.For this purpose,first we derive the power spectra of
comoving curvature perturbation and primordial gravitational waves in a
positively curved FLRW universe according to the slowly rolling inflationary
senario. It can be shown that the curvature spectral index in this model
automatically has a small negative running parameter which is compatible with
observational measurements.Then,by taking into account the curvature factor,we
investigate the relative amplitude of the scalar and tensor perturbations.It
would be clarified that the tensor-scalar ratio for this model against the
spatially flat one,depends on the waelength of the perturbative models
directly.Comment: 21 pages,n o figure
Evolution of the spectral index after inflation
In this article we investigate the time evolution of the adiabatic(curvature)
and isocurvature (entropy) spectral indices after end of inflation for all
cosmological scales and two different initial conditions. For this purpose,we
first extract an explicit equation for the time evolution of the comoving
curvature perturbation (which may be known as the generalized Mukhanov-Sasaki
equation). It shall be manifested that the evolution of adibatic spectral index
severely depends on the intial conditions and just for the super-Hubble scales
and adiabatic initial conditions is constat as be expected.Moreover,it shall be
clear that the adiabatic spectral index after recombination approach to a
constant value for the isocurvature perturbations.Finally,we re-investgate the
Sachs-Wolfe effect and show that the fudge factor 1/3 in the adiabatic ordinary
Sachs-Wolfe formula must be replaced by 0.4.Comment: 18 pages,4figure
The effect of sublattice symmetry breaking on the electronic properties of a doped graphene
Motivated by a number of recent experimental studies, we have carried out the
microscopic calculation of the quasiparticle self-energy and spectral function
in a doped graphene when a symmetry breaking of the sublattices is occurred.
Our systematic study is based on the many-body GW approach that is
established on the random phase approximation and on graphene's massive Dirac
equation continuum model. We report extensive calculations of both the real and
imaginary parts of the quasiparticle self-energy in the presence of a gap
opening. We also present results for spectral function, renormalized Fermi
velocity and band gap renormalization of massive Dirac Fermions over a broad
range of electron densities. We further show that the mass generating in
graphene washes out the plasmaron peak in spectral weight.Comment: 22 Pages, 10 Figure
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A Jini-Based Solution for Electronic Prescriptions
In most countries today, handwritten, paper-based
medical prescriptions are the norm.While efforts have been made in the past and are being made at present to migrate toward electronic dispensation of prescriptions, these have generally omitted to incorporate ubiquitous computing technology in their proposed solutions. In this paper, we focus on this issue and describe a Jini-based prototypical solution for electronic prescriptions, which allows for their wireless transmission to in-range pharmacies and the augmentation of the service levels rendered to the user, with, for instance, information about queue lengths and estimated waiting times being provided to the patients. Clinical and user evaluation revealed that there were high levels of
agreement as regards the prototype’s effectiveness, ease of use, and usefulness
On the perturbation theory in spatially closed background
In this article,we investigate some features of the perturbation theory in
spatially closed universe. We will show that the perturbative field equations
in a spatially closed universe always have two independent adiabatic solutions
provided that the wavelengths of perturbation modes are very longer than the
Hubble horizon. It will be revealed that these adiabatic solutions do not
depend on the curvature directly. We also propound a new interpretation for the
curvature perturbation in terms of the unperturbed geometry.Comment: 25 pages,no figures,accepted for publiction in EPJ
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