8 research outputs found
Validity of Thermodynamical Laws in Dark Energy Filled Universe
We have considered the flat FRW model of the universe which is filled with
only dark energy. The general descriptions of first and second laws of
thermodynamics are investigated on the apparent horizon and event horizon of
the universe. We have assumed the equation of state of three different types of
dark energy models. We have examined the validity of first and second laws of
thermodynamics on apparent and event horizons for these dark energies. For
these dark energy models, it has been found that on the apparent horizon, first
and second laws are always valid. On the event horizon, the laws are break down
for dark energy models 1 and 2. For model 3, first law cannot be satisfied on
the event horizon, but second law may be satisfied at the late stage of the
evolution of the universe and so the validity of second law on the event
horizon depends on the values of the parameters only.Comment: 9 pages, 6 figure
Brans-Dicke Theory and Thermodynamical Laws on Apparent and Event Horizons
In this work, we have described the Brans-Dicke theory of gravity and given a
particular solution by choosing a power law form of scalar field and
constant . If we assume first law and entropy formula on apparent
horizon then we recover Friedmann equations. Next, assuming first law of
thermodynamics, the validity conditions of GSL on event horizon are presented.
Also without use first law, if we impose the entropy relation on the horizon,
then we also obtain the condition of validity of GSL on event horizon. The
validity of GSL completely depends on the model of BD scalar field solutions.
We have justified that on the apparent horizon the two process are equivalent,
but on the event horizon they are not equivalent. If first law is valid on the
event horizon then GSL may be satisfied in BD solution, but if first law is not
satisfied then GSL is not satisfied in BD solution. So first law always favours
GSL on event horizon. In our effective approach, the first law and GSL is
always satisfied in apparent horizon, which do not depend on BD theory of
gravity.Comment: 6 pages, 2 figure
Thermodynamical Laws in Horava-Lifshitz Gravity
In this work, we have investigated the validity of GSL of thermodynamics in a
universe (open, closed and flat) governed by Hoava-Lifshitz
gravity. If the universe contains barotropic fluid the corresponding solutions
have been obtained. The validity of GSL have been examined by two approaches:
(i) robust approach and (ii) effective approach. In robust approach, we have
considered the universe contains only matter fluid and the effect of the
gravitational sector of HL gravity was incorporated through the modified black
hole entropy on the horizon. Effective approach is that all extra information
of HL gravity into an effective dark energy fluid and so we consider the
universe contains matter fluid plus this effective fluid. This approach is
essentially same as the Einstein's gravity theory. The general prescription for
validity of GSL have been discussed. Graphically we have shown that the GSL may
be satisfied for open, closed and flat universe on the different horizons with
different conditions.Comment: 7 latex pages, 7 figure
Thermodynamics of Modified Chaplygin Gas and Tachyonic Field
Here we generalize the results of the work of ref. [10] in modified Chaplygin
gas model and tachyonic field model. Here we have studied the thermodynamical
behaviour and the equation of state in terms of volume and temperature for both
models. We have used the solution and the corresponding equation of state of
our previous work [12] for tachyonic field model. We have also studied the
thermodynamical stability using thermal equation of state for the tachyonic
field model and have shown that there is no critical points during
thermodynamical expansion. The determination of due to expansion for
the tachyonic field have been discussed by assuming some initial conditions.
Here, the thermal quantities have been investigated using some reduced
parameters.Comment: 10 page
Study of Thermodynamic Quantities in Generalized Gravity Theories
In this work, we have studied the thermodynamic quantities like temperature
of the universe, heat capacity and squared speed of sound in generalized
gravity theories like Brans-Dicke, Hoava-Lifshitz and
gravities. We have considered the universe filled with dark matter and dark
energy. Also we have considered the equation of state parameters for open,
closed and flat models. We have observed that in all cases the equation of
state behaves like quintessence. The temperature and heat capacity of the
universe are found to decrease with the expansion of the universe in all cases.
In Brans-Dicke and gravity theories the squared speed of sound is found
to exhibit increasing behavior for open, closed and flat models and in
Hoava-Lifshitz gravity theory it is found to exhibit
decreasing behavior for open and closed models with the evolution of the
universe. However, for flat universe, the squared speed of sound remains
constant in Hoava-Lifshitz gravity.Comment: 15 pages, 12 figure
Roles of GM-CSF in the Pathogenesis of Autoimmune Diseases: An Update.
Granulocyte-macrophage colony-stimulating factor (GM-CSF) was first described as a growth factor that induces the differentiation and proliferation of myeloid progenitors in the bone marrow. GM-CSF also has an important cytokine effect in chronic inflammatory diseases by stimulating the activation and migration of myeloid cells to inflammation sites, promoting survival of target cells and stimulating the renewal of effector granulocytes and macrophages. Because of these pro-cellular effects, an imbalance in GM-CSF production/signaling may lead to harmful inflammatory conditions. In this context, GM-CSF has a pathogenic role in autoimmune diseases that are dependent on cellular immune responses such as multiple sclerosis (MS) and rheumatoid arthritis (RA). Conversely, a protective role has also been described in other autoimmune diseases where humoral responses are detrimental such as myasthenia gravis (MG), Hashimoto\u27s thyroiditis (HT), inflammatory bowel disease (IBD), and systemic lupus erythematosus (SLE). In this review, we aimed for a comprehensive analysis of literature data on the multiple roles of GM-CSF in autoimmue diseases and possible therapeutic strategies that target GM-CSF production
Study of Thermodynamics in Generalized Holographic and Ricci Dark Energy Models
We have considered the flat FRW model of the universe which is filled with
the combination of dark matter and dark energy. Here we have considered two
types of dark energy models: (i) Generalized holographic and (ii) generalized
Ricci dark energies. The general descriptions of first law and generalized
second law (GSL) of thermodynamics have studied on the apparent horizon,
particle horizon and event horizon of the universe. We have shown that the
first law and GSL are always valid on apparent horizon and first law can not be
satisfied on the particle and event horizons in Einstein's gravity. These
results are always true for any types of dark energy models i.e., these results
do not depend on the dark energy models in Einstein's gravity. But the GSL
completely depends on the choices of dark energy models in Einstein's gravity.
Here we have discussed the validity of GSL in Generalized holographic and
generalized Ricci dark energy models. On the particle horizon GSL may be
satisfied but on the event horizon the GSL can not be satisfied for both the
dark energy models. Also we have considered the Generalized holographic dark
energy and generalized Ricci dark energy as the original holographic dark
energy, so in this situation we have calculated the expression of the radius of
the horizon . On this horizon, we have shown that the first law can not be
satisfied. Finally, on the horizon of radius , we have found that the GSL
can not be satisfied for both the dark energy models.Comment: 11 pages, 3 figure