15,281 research outputs found
Curvature Inspired Cosmological Scenario
Using modified gravity with non-linear terms of curvature, and (with being the positive real number and being the scalar
curvature), cosmological scenario,beginning at the Planck scale, is obtained.
Here, a unified picture of cosmology is obtained from gravity. In this
scenario, universe begins with power-law inflation, followed by deceleration
and acceleration in the late universe as well as possible collapse of the
universe in future. It is different from dark energy models with
non-linear curvature terms assumed as dark energy. Here, dark energy terms are
induced by linear as well as non-linear terms of curvature in Friedmann
equation being derived from modified gravity.It is also interesting to see
that, in this model, dark radiation and dark matter terms emerge spontaneously
from the gravitational sector. It is found that dark energy, obtained here,
behaves as quintessence in the early universe and phantom in the late universe.
Moreover, analogous to brane-tension in brane-gravity inspired Friedmann
equation, a tension term arises here being called as cosmic tension.
It is found that, in the late universe, Friedmann equation (obtained here)
contains a term ( being the phantom energy density)
analogous to a similar term in Friedmann equation with loop quantum effects, if
and brane-gravity correction when Comment: 19 Pages. To appear in Int. J. Thro. Phy
Cosmic Evolution with Early and Late Acceleration Inspired by Dual Nature of the Ricci Scalar Curvature
In the present paper, it is found that dark energy emerges spontaneously from
the modified gravity. According to cosmological scenario, obtained here, the
universe inflates for sec. in the beginning and late universe
accelerates after 8.58 Gyrs. During the long intermediate period, it
decelerates driven by radiation and subsequently by matter. Emerged
gravitational dark energy mimics quintessence and its density falls by 115
orders from its initial value to its current
value .Comment: 40 pages. To appearin Int. J. Mod. Phys.
Landau Ghosts and Anti-Ghosts in Condensed Matter and High Density Hadronic Matter
It is observed that the ``ghost'' (originally discovered by Landau in quantum
electro-dynamics) and its counterparts in other theories are indeed ubiquitous
as they occur in a one-loop approximation to any conventional (unbroken) gauge
theory. The mechanism is first exposed in its generality via the Dyson equation
and a simple but explicit example in condensed matter is provided through the
static Clausius-Mossotti and its dynamic counterpart the Lorenz-Lorentz
equation. The physical phase transition phenomenon associated with it is found
to be super-radiance. We verify quantitatively that water (and many other polar
liquids) are indeed super-radiant at room temperature. In quantum
chromo-dynamics on the other hand, we encounter, thanks to asymptotic freedom,
an ``anti-ghost'' which is closely associated with color confinement. Thus, in
QCD, free quarks and glue exist in a super-radiant phase and hadronic matter in
the normal one.Comment: LaTeX 12 Pages and 2 *.eps Figure
Numerical Study of the Lowest Energy Configurations for Global String-Antistring Pairs
We investigate the lowest energy configurations for string - antistring pairs
at fixed separations by numerically minimizing the energy. We show that for
separations smaller than a critical value, a region of false vacuum develops in
the middle due to large gradient energy density. Consequently, well defined
string - antistring pairs do not exist for such separations. We present an
example of vortex - antivortex production by vacuum bubbles where this effect
seems to play a dynamical role in the annihilation of the pair. We also study
the dependence of the energy of an string-antistring pair on their separation
and find deviations from a simple logarithmic dependence for small separations.Comment: 14 pages, in LATEX, 7 figures (not included
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