351 research outputs found
COLECCIÓN FOTOGRÁFICA DEL REAL CLUB VICTORIA [Material gráfico]
Copia digital. Madrid : Ministerio de Educación, Cultura y Deporte. Subdirección General de Coordinación Bibliotecaria, 201
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.
The effect of geometry on charge confinement in three dimensions
We show that, in contrast to the flat case, the Maxwell theory is not
confining in the background of the three dimensional BTZ black-hole (covering
space). We also study the effect of the curvature on screening behavior of
Maxwell-Chern-Simons model in this space-time.Comment: 8 pages. To be published in Europhysics Letter
Time variable cosmological constant of holographic origin with interaction in Brans-Dicke theory
Time variable cosmological constant (TVCC) of holographic origin with
interaction in Brans-Dicke theory is discussed in this paper. We investigate
some characters for this model, and show the evolutions of deceleration
parameter and equation of state (EOS) for dark energy. It is shown that in this
scenario an accelerating universe can be obtained and the evolution of EOS for
dark energy can cross over the boundary of phantom divide. In addition, a
geometrical diagnostic method, jerk parameter is applied to this model to
distinguish it with cosmological constant.Comment: 10 pages, 9 figure
Electrostatic self-energy and Bekenstein entropy bound in the massive Schwinger model
We obtain the electrostatic energy of two opposite charges near the horizon
of stationary black-holes in the massive Schwinger model. Besides the confining
aspects of the model, we discuss the Bekenstein entropy upper bound of a
charged object using the generalized second law. We show that despite the
massless case, in the massive Schwinger model the entropy of the black hole and
consequently the Bekenstein bound are altered by the vacuum polarization.Comment: 14 pages, accepted for publication in "Gen. Rel. Grav. (2005)
Diffusive transport of light in two-dimensional granular materials
We study photon diffusion in a two-dimensional random packing of monodisperse
disks as a simple model of granular material. We apply ray optics approximation
to set up a persistent random walk for the photons. We employ Fresnel's
intensity reflectance with its rich dependence on the incidence angle and
polarization state of the light. We present an analytic expression for the
transport-mean-free path in terms of the refractive indices of grains and host
medium, grain radius, and packing fraction. We perform numerical simulations to
examine our analytical result.Comment: 9 pages, 3 figure
Statefinder and Om Diagnostics for Interacting New Holographic Dark Energy Model and Generalized Second Law of Thermodynamics
In this work, we have considered that the flat FRW universe is filled with
the mixture of dark matter and the new holographic dark energy. If there is an
interaction, we have investigated the natures of deceleration parameter,
statefinder and diagnostics. We have examined the validity of the first
and generalized second laws of thermodynamics under these interactions on the
event as well as apparent horizon. It has been observed that the first law is
violated on the event horizon. However, the generalized second law is valid
throughout the evolution of the universe enveloped by the apparent horizon.
When the event horizon is considered as the enveloping horizon, the generalized
second law is found to break down excepting at late stage of the universe.Comment: 9 pages, 13 figure
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