10,617 research outputs found
Hawking radiation and thermodynamics of dynamical black holes in phantom dominated universe
The thermodynamic properties of dark energy-dominated universe in the
presence of a black hole are investigated in the general case of a varying
equation-of-state-parameter . We show that all the thermodynamics
quantities are regular at the phantom divide crossing, and particularly the
temperature and the entropy of the dark fluid are always positive definite. We
also study the accretion process of a phantom fluid by black holes and the
conditions required for the validity of the generalized second law of
thermodynamics. As a results we obtain a strictly negative chemical potential
and an equation-of-state parameter Comment: 22 pages,3 figure
Validity of the Generalized Second Law of Thermodynamics of the Universe Bounded by the Event Horizon in Holographic Dark Energy Model
In this letter, we investigate the validity of the generalized second law of
thermodynamics of the universe bounded by the event horizon in the holographic
dark energy model. The universe is chosen to be homogeneous and isotropic and
the validity of the first law has been assumed here. The matter in the universe
is taken in the form of non-interacting two fluid system- one component is the
holographic dark energy model and the other component is in the form of dust.Comment: 8 page
Thermodynamics and dark energy
A significant observational effort has been directed to unveil the nature of
the so-called dark energy. However, given the large number of theoretical
possibilities, it is possible that such a task cannot be performed on the basis
only of the observational data. In this article we discuss some thermodynamic
properties of this energy component by assuming that its constituents are
massless quanta with a general time-dependent equation-of-state parameter
, where and are
constants and may assume different forms. We show that very restrictive
bounds can be placed on the - space when current observational data
are combined with the thermodynamic constraints derived.Comment: 5 pages, 3 figures, LaTe
The Holographic Model of Dark Energy and Thermodynamics of Non-Flat Accelerated Expanding Universe
Motivated by recent results on non-vanishing spatial curvature \cite{curve}
we employ the holographic model of dark energy to investigate the validity of
first and second laws of thermodynamics in non-flat (closed) universe enclosed
by apparent horizon and the event horizon measured from the sphere of
horizon named . We show that for the apparent horizon the first law is
roughly respected for different epochs while the second laws of thermodynamics
is respected while for as the system's IR cut-off first law is broken down
and second law is respected for special range of deceleration parameter. It is
also shown that at late-time universe is equal to and the
thermodynamic laws are hold, when the universe has non-vanishing curvature.
Defining the fluid temperature to be proportional to horizon temperature the
range for coefficient of proportionality is obtained provided that the
generalized second law of thermodynamics is hold.Comment: 12 pages, no figure, abstract and text extended, references added,
accepted for publication in JCA
Interacting holographic dark energy model and generalized second law of thermodynamics in non-flat universe
In the present paper we consider the interacting holographic model of dark
energy to investigate the validity of the generalized second laws of
thermodynamics in non-flat (closed) universe enclosed by the event horizon
measured from the sphere of the horizon named . We show that for as the
system's IR cut-off the generalized second law is respected for the special
range of the deceleration parameter.Comment: 11 pages, no figure
Rotating metrics admitting non-perfect fluids in General Relativity
In this paper, by applying Newman-Janis algorithm in spherical symmetric
metrics, a class of embedded rotating solutions of field equations is
presented. These solutions admit non-perfect fluidsComment: LaTex, 39 page
Alkaloids as alternative probes to characterize the relative hydrophobicity of aqueous biphasic systems
In order to overcome the lack of characterization on the relative hydrophobicity of
aqueous biphasic systems (ABS), the partition of three alkaloids as alternative probes,
was evaluated in a series of biocompatible ABS composed of cholinium-based salts or
ionic liquids (ILs) and polyethylene glycol (PEG). The caffeine partitioning in ABS was
firstly addressed to infer on the effect of the phase-forming components composition. In
all systems, caffeine preferentially concentrates in the lower water content PEG-rich
phase. Additionally, a linear dependence between the logarithmic function of the
partition coefficients and the water content ratio was found. To confirm this linear
dependency, the partition coefficients of caffeine, theobromine and theophylline were
determined in other ABS formed by different cholinium-based salts/ILs. In most
systems, it is shown that all alkaloids partition to the most hydrophobic phase. To
support the experimental results, COSMO-RS (Conductor-like Screening Model for
Real Solvents) was used to compute the screening charge distributions of both phaseforming
components of ABS and alkaloids, the excess enthalpy of mixing and the
activity coefficients at infinite dilution. It is here demonstrated that the partition trend of
alkaloids can be used to address the relative hydrophobicity of the coexisting phases in
polymer-salt/-IL ABS
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