9 research outputs found
Tsallis holographic dark energy under Complex form of Quintessence model
In this paper, we use a Tsallis holographic dark energy model in two forms,
interacting and non-interacting cases, to acquire some parameters as the
equation of state for the energy density of the Tsallis model in the FRW
universe concerning the complex form of quintessence model. We will study the
cosmology of complex quintessence by revamping the potential and investigating
the scalar field dynamics. Then we analyze () and stability in
two cases, i.e., non-interacting and interacting. We will explore whether these
cases describe a real universe by calculating fractional energy density
and concerning two parts of the quintessence field effect (
complex and real part ) by considering the real part of this field to be a
slow-roll field. We know that the part in which the fractional energy density
() does not describe a real universe. Also, we specified an
interacting coupling parameter that depends on the constant parameter
of the Tsallis holographic model () with respect to fractional energy
density (). Unlike independence between the fractional energy density and
interacting coupling in the real quintessence model, we determine a
relationship among these parameters in this theory. Finally, by plotting some
figures, we specify the features of () and () in
two cases and compare the result with each other.Comment: 22 pages, 4 figures, Accepted for publication in Communications in
Theoretical Physic
Weak Gravity Conjecture, Black Branes and Violations of Universal Thermodynamic Relation
The universal thermodynamic relations between corrections to entropy and
extremality for various black holes solutions have been studied. In this
regard, we hereby consider a number of different black brane solutions in
different structures for perturbative corrections to general relativity. These
are, namely, black brane solution in Rastall AdS massive gravity,
Einstein-Yang-Mills AdS black brane solution in massive gravity and general
anisotropic black brane in Horava-Lifshitz gravity. We calculate both the
entropy and extremality bound by introducing a small constant correction to the
action. Remarkably, we find that black brane violates the universal
thermodynamic relations. In other words, a universal relation between
corrections to entropy and extremality are not valid in the black brane
structure.Comment: 14 pages; 2 captioned figure
Further Refining Swampland dS Conjecture in Mimetic f(G) Gravity
Mimetic gravity analysis has been studied as a theory in various types of
general relativity extensions, such as mimetic f(R) gravity, mimetic f(R, T)
gravity, mimetic f(R, G) gravity, etc., in the literature. This paper presents
a set of equations arising from mimetic conditions and studies cosmic inflation
with a combination of mimetic f(G) gravity and swampland dS conjectures. We
analyze and evaluate these results. Therefore, we first thoroughly introduce
the mimetic f(G) gravity and calculate some cosmological parameters such as the
scalar spectral index, the tensor-to-scalar ratio, and the slow-roll
parameters. Also, we investigate the potential according to the mimetic f(G)
gravity. Then we will challenge the swampland dS conjectures with this
condition. By expressing the coefficient of swampland dS conjectures viz
and in terms of and , we plot some figures and
determine the allowable range for each of these cosmological parameters and
these coefficients, and finally, compare these results with observable data
such as Planck and BICEP2/Keck array data. We show and are not
, so the refining swampland dS conjecture is not satisfied for
this inflationary model. Then we examine it with further refining swampland dS
conjecture, which has a series of free parameters such as , , and
. By adjusting these parameters, the compatibility of the mentioned
conjecture with the inflationary model can be discussed. We determine the
further refining swampland dS conjecture is satisfied. when , we can always find , and whose value is
larger than 2, viz for , we find , which we can
choose according to the condition . Also we know
, so we will have .Comment: 25 pages, 5 figures. Accepted for publication in International
Journal of Modern Physics D (This work is dedicated to the memory of Prof
Farhad Darabi
Thermodynamic topology and photon spheres in the Hyperscaling violation black hole
It was shown that a standard ring of light can be imagined outside the event
horizon for stationary rotating four-dimensional black holes with axial
symmetry using the topological method. Based on this concept, in this paper, we
investigate the topological charge and the conditions of existence of the
photon sphere (PS) for a hyperscaling violation (HSV) black hole with various
values of the parameters of this model. Then, after carrying out a detailed
analysis, we show the conventional topological classes viz for the
mentioned black hole and for the naked singularities. Also, we propose a
new topological class for naked singularities () with respect to .
Then, we will use two different methods, namely the temperature (Duan's
topological current -mapping theory) and the generalized Helmholtz free
energy method, to study the topological classes of our black hole. By
considering the black hole mentioned, we discuss the critical and zero points
(topological charges and topological numbers) for different parameters of
hyperscaling violating black holes, such as () and other free
parameters, and study their thermodynamic topology. We observe that for a given
value of the parameters , , and other free parameters, there exist
two total topological charges for the method and two total
topological numbers for the generalized Helmholtz free energy method.
Additionally, we summarize the results for each study as photon sphere,
temperature, and generalized Helmholtz free energy in some figures and tables.
Finally, we compare our findings with other related studies in the literature.Comment: 38 pages, 21 figures and 13 table
Cosmic evolution of the logarithmic f(R) model and the dS swampland conjecture
In this paper, we study the inflationary scenario in logarithmic f(R)
gravity, where the rate of inflation roll is constant. On the other hand, our
gravitational f(R) model is a polynomial plus a logarithmic term. We take
advantage of constant-roll conditions and investigate the cosmic evolution of
the logarithmic f(R) gravity. Therefore, we plot some figures such as the
scalar spectrum index and tensor-to-scaler ratio concerning ,
and model's constant parameters, i.e., , and
respectively. Also, we obtain the potential by using the constant roll
condition. We know that the potential value obtained with this condition has an
exact value. Next, we challenge it with refined swampland conjecture with
respect to the Planck data. Finally, we compare our results with the
experimental data, especially Planck 2018.Comment: 20pages, 5 figure
Bardeen Black Hole Thermodynamics from Topological Perspective
In this paper, we use the generalized off-shell Helmholtz free energy method
to explore the thermodynamic properties of Bardeen black holes (BD BHs) from a
topological perspective based on Duan's topological current -mapping. We
consider various structures of BD BHs, including regular BD-AdS BHs, BD-AdS BHs
in Kiselev's model of quintessence, BD BHs in massive gravity (MG), and BD BHs
in 4D Einstein-Gauss-Bonnet (EGB) gravity. We demonstrate that these BHs have
one topological classification (TC), i.e., TC is +1 for all BHs considered, and
the addition of MG or GB terms, etc., does not change the topological numbers.Comment: 16 pages, 4 figures, 1 table, Accepted for publication in the Annals
of Physic
Bulk-boundary and RPS Thermodynamics from Topology perspective
In this article, we investigate the bulk-boundary and restricted phase space
(RPS) thermodynamics of Rissner-Nordstr\"om (R-N) AdS and 6-dimensional charged
Gauss-Bonnet AdS black holes. Also, we examine the topological characteristics
of the considered black holes and compare them with the extended thermodynamics
results. In fact, we have found that the topological behavior of the
bulk-boundary thermodynamics is the same as that of the extended
thermodynamics, whereas the RPS thermodynamics exhibits a distinct behavior. We
also demonstrate that within the RPS formalism, there is only one critical
point with a topological charge of +1 . Additionally, for RPS
formalism, the inclusion of higher derivative curvature terms in the form of
Gauss-Bonnet gravity does not alter the topological classification of critical
points in charged AdS black holes.Comment: 17 pages, 6 figures, 1 Tabl
Anisotropic constant-roll inflation with noncommutative model and swampland conjectures
In this paper, we study a constant-roll inflationary model in the presence of a noncommutative parameter with a homogeneous scalar field minimally coupled to gravity. The specific noncommutative inflation conditions proposed new consequences. On the other hand, we use anisotropic conditions and find new anisotropic constant-roll solutions with respect to noncommutative parameter. Also, we will plot some figures with respect to the specific values of the corresponding parameter and the swampland criteria which is raised from the exact potential obtained from the constant-roll condition. Finally, different of figures lead us to analyze the corresponding results and also show the effect of above mentioned parameter on the inflationary model
de Sitter swampland conjecture in string field inflation
Abstract In this paper, we study a particular type of inflation by using non-local Friedman equations that are derived from the zero levels of string field theory and express a tachyonic action. Then, we challenge it by further refining de Sitter (dS) swampland conjecture (FRdSSC) monitoring. Therefore, we investigate some quantities, such as potential and Hubble parameters. We also consider slow-roll parameters to examine quantities such as the scalar spectrum index and the tensor-to-scalar ratio. Using straightforward calculations, we investigate this model from the swampland conjecture perspective in terms of the cosmological parameters, i.e., ( n s ), (r), and observable data such as Planck 2018, by constructing some structures such as ( c 1 , 2 - n s ) and ( c 1 , 2 - r s ) . Then, we make a new restriction for this conjecture as c 1 2 c 2 2 and get a limit for this model in the range a , b > 0 , a + b = 1 , and q > 2 . By setting these parameters, we examine the compatibility of the mentioned conjecture with this inflationary model. Finally, we infer from this string field inflation (SFI) model that it satisfies the FRdSSC with the constraint of its free parameters a, b, and q