975 research outputs found
Quantum corrections to the conductivity of fermion - gauge field models: Application to half filled Landau level and high- superconductors
We calculate the Altshuler-Aronov type quantum correction to the conductivity
of charge carriers in a random potential (or random magnetic field)
coupled to a transverse gauge field. The gauge fields considered simulate the
effect of the Coulomb interaction for the fractional quantum Hall state at half
filling and for the model of high- superconducting compounds. We
find an unusually large quantum correction varying linearly or quadratically
with the logarithm of temperature, in different temperature regimes.Comment: 12 pages REVTEX, 1 figure. The figure is added and minor misprints
are correcte
Dark Energy Accretion onto black holes in a cosmic scenario
In this paper we study the accretion of dark energy onto a black hole in the
cases that dark energy is equipped with a positive cosmological constant and
when the space-time is described by a Schwarzschild-de Sitter metric. It is
shown that, if confronted with current observational data, the results derived
when no cosmological constant is present are once again obtained in both cases.Comment: 7 pages, 3 figure
A new viable region of the inert doublet model
The inert doublet model, a minimal extension of the Standard Model by a
second Higgs doublet, is one of the simplest and most attractive scenarios that
can explain the dark matter. In this paper, we demonstrate the existence of a
new viable region of the inert doublet model featuring dark matter masses
between Mw and about 160 GeV. Along this previously overlooked region of the
parameter space, the correct relic density is obtained thanks to cancellations
between different diagrams contributing to dark matter annihilation into gauge
bosons (W+W- and ZZ). First, we explain how these cancellations come about and
show several examples illustrating the effect of the parameters of the model on
the cancellations themselves and on the predicted relic density. Then, we
perform a full scan of the new viable region and analyze it in detail by
projecting it onto several two-dimensional planes. Finally, the prospects for
the direct and the indirect detection of inert Higgs dark matter within this
new viable region are studied. We find that present direct detection bounds
already rule out a fraction of the new parameter space and that future direct
detection experiments, such as Xenon100, will easily probe the remaining part
in its entirety.Comment: 27 pages, 16 figure
in interacting quintessence model
A model consisting of quintessence scalar field interacting with cold dark
matter is considered. Conditions required to reach are discussed. It
is shown that depending on the potential considered for the quintessence,
reaching the phantom divide line puts some constraints on the interaction
between dark energy and dark matter. This also may determine the ratio of dark
matter to dark energy density at .Comment: 10 pages, references updated, some notes added, minor changes
applied, accepted for publication in Eur. Phys. J.
Accuracy of a method based on atomic absorption spectrometry to determine inorganic arsenic in food : Outcome of the collaborative trial IMEP-41
Peer reviewedPublisher PD
Non linear equation of state and effective phantom divide in brane models
Here, DGP model of brane-gravity is analyzed and compared with the standard
general relativity and Randall-Sundrum cases using non-linear equation of
state. Phantom fluid is known to violate the weak energy condition. In this
paper, it is found that this characteristic of phantom energy is affected
drastically by the negative brane-tension of the RS-II model. It is
found that in DGP model strong energy condition(SEC) is always violated and the
universe accelerates only where as in RS-II model even SEC is not violated for
and the universe decelerates
Scalar field exact solutions for non-flat FLRW cosmology: A technique from non-linear Schr\"odinger-type formulation
We report a method of solving for canonical scalar field exact solution in a
non-flat FLRW universe with barotropic fluid using non-linear Schr\"{o}dinger
(NLS)-type formulation in comparison to the method in the standard Friedmann
framework. We consider phantom and non-phantom scalar field cases with
exponential and power-law accelerating expansion. Analysis on effective
equation of state to both cases of expansion is also performed. We speculate
and comment on some advantage and disadvantage of using the NLS formulation in
solving for the exact solution.Comment: 12 pages, GERG format, Reference added. accepted by Gen. Relativ. and
Gra
Composite Fermions and the Energy Gap in the Fractional Quantum Hall Effect
The energy gaps for the fractional quantum Hall effect at filling fractions
1/3, 1/5, and 1/7 have been calculated by variational Monte Carlo using Jain's
composite fermion wave functions before and after projection onto the lowest
Landau level. Before projection there is a contribution to the energy gaps from
the first excited Landau level. After projection this contribution vanishes,
the quasielectron charge becomes more localized, and the Coulomb energy
contribution increases. The projected gaps agree well with previous
calculations, lending support to the composite fermion theory.Comment: 12 pages, Revtex 3.0, 2 compressed and uuencoded postscript figures
appended, NHMFL-94-062
Expanding Universe: Thermodynamical Aspects From Different Models
The pivotal point of the paper is to discuss the behavior of temperature,
pressure, energy density as a function of volume along with determination of
caloric EoS from following two model: & .
The time scale of instability for this two models is discussed. In the paper we
then generalize our result and arrive at general expression for energy density
irrespective of the model. The thermodynamical stability for both of the model
and the general case is discussed from this viewpoint. We also arrive at a
condition on the limiting behavior of thermodynamic parameter to validate the
third law of thermodynamics and interpret the general mathematical expression
of integration constant (what we get while integrating energy
conservation equation) physically relating it to number of micro states. The
constraint on the allowed values of the parameters of the models is discussed
which ascertains stability of universe. The validity of thermodynamical laws
within apparent and event horizon is discussed.Comment: 16 pages, 3 figures(Accepted for publication in "Astrophysics and
Space Science"
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