194 research outputs found
Parton distribution functions and constraints on the intrinsic charm content of the proton using BHPS approach
In this work, a new set of parton distribution functions taking into account
the intrinsic charm (IC) contribution is presented. We focus on the impact of
the EMC measurements on the large charm structure function as the strongest
evidence for the intrinsic charm when combined with the HERA, SLAC and BCDMS
data. The main goal of this paper is the simultaneous determination of the
intrinsic charm probability and strong coupling .
This allows us to study the interaction of these two quantities as well as the
influence on the PDFs in the presence of IC contributions. By considering
which can be fix or free parameter from our QCD analysis, we find
that although there is not a significant change in the extracted central value
of PDFs and their uncertainties, the obtained value of
change by factor 7.8\%. The extracted value of in the
present QCD analysis is consistent with the recent reported upper limit of
, which is obtained for the first time from LHC measurements. We show
the intrinsic charm probability is sensitive to the strong coupling constant
and also the charm mass. The extracted value of the strong coupling constant
at NLO is in good agreement with world
average value and available theoretical models.Comment: 21 pages, 10 figures, 6 table
Reconstructing f(T)-gravity from the polytropic and different Chaplygin gas dark energy models
Motivated by a recent work of us [1], we reconstruct the different
f(T)-gravity models corresponding to a set of dark energy scenarios containing
the polytropic, the standard Chaplygin, the generalized Chaplygin and the
modified Chaplygin gas models. We also derive the equation of state parameter
of the selected f(T)-gravity models and obtain the necessary conditions for
crossing the phantom-divide line.Comment: 7 page
Generalized second law of thermodynamics on the apparent horizon in modified Gauss-Bonnet gravity
Modified gravity and generalized second law (GSL) of thermodynamics are
interesting topics in the modern cosmology. In this regard, we investigate the
GSL of gravitational thermodynamics in the framework of modified Gauss-Bonnet
gravity or f(G)-gravity. We consider a spatially FRW universe filled with the
matter and radiation enclosed by the dynamical apparent horizon with the
Hawking temperature. For two viable f(G) models, we first numerically solve the
set of differential equations governing the dynamics of f(G)-gravity. Then, we
obtain the evolutions of the Hubble parameter, the Gauss-Bonnet curvature
invariant term, the density and equation of state parameters as well as the
deceleration parameter. In addition, we check the energy conditions for both
models and finally examine the validity of the GSL. For the selected f(G)
models, we conclude that both models have a stable de Sitter attractor. The
equation of state parameters behave quite similar to those of the LCDM model in
the radiation/matter dominated epochs, then they enter the phantom region
before reaching the de Sitter attractor with w=-1. The deceleration parameter
starts from the radiation/matter dominated eras, then transits from a cosmic
deceleration to acceleration and finally approaches a de Sitter regime at late
times, as expected. Furthermore, the GSL is respected for both models during
the standard radiation/matter dominated epochs. Thereafter when the universe
becomes accelerating, the GSL is violated in some ranges of scale factor. At
late times, the evolution of the GSL predicts an adiabatic behavior for the
accelerated expansion of the universe.Comment: 21 pages, 18 figure
Generalized second law of thermodynamics in scalar-tensor gravity
Within the context of scalar-tensor gravity, we explore the generalized
second law (GSL) of gravitational thermodynamics. We extend the action of
ordinary scalar-tensor gravity theory to the case in which there is a
non-minimal coupling between the scalar field and the matter field (as
chameleon field). Then, we derive the field equations governing the gravity and
the scalar field. For a FRW universe filled only with ordinary matter, we
obtain the modified Friedmann equations as well as the evolution equation of
the scalar field. Furthermore, we assume the boundary of the universe to be
enclosed by the dynamical apparent horizon which is in thermal equilibrium with
the Hawking temperature. We obtain a general expression for the GSL of
thermodynamics in the scalar-tensor gravity model. For some viable
scalar-tensor models, we first obtain the evolutionary behaviors of the matter
density, the scale factor, the Hubble parameter, the scalar field, the
deceleration parameter as well as the effective equation of state (EoS)
parameter. We conclude that in most of the models, the deceleration parameter
approaches a de Sitter regime at late times, as expected. Also the effective
EoS parameter acts like the LCDM model at late times. Finally, we examine the
validity of the GSL for the selected models.Comment: 27 pages, 5 figure
QCD analysis of structure functions in deep inelastic neutrino-nucleon scattering without using the orthogonal polynomials approach
A nonsinglet QCD analysis of neutrino-nucleon structure function is performed
based on all the data for charged current neutrino-nucleon deep inelastic
scattering (DIS) corresponds to NLO and NNLO approximations, with taking into
account the nuclear and higher twist corrections. In this analysis, we extract
and valence parton distribution functions (PDFs) in
a wide range of and , and determine their parametrization with the
correlated errors using the xFitter framework. Our results regarding
valence-quark densities with their uncertainties are compared to the prediction
extracted using other PDF sets from different groups. We determine
= 0.1199 0.0031 and 0.1185 0.0023 with
considering the nuclear and higher twist corrections at the NLO and NNLO,
respectively, and perform a comparison with other reported results. The
extracted results regarding valence-quark distributions and the value of
are in good agreement with available theoretical models.Comment: 35 pages, 9 figures and 3 Table
Power-law and intermediate inflationary models in f(T)-gravity
We study inflation in the framework of -gravity in the presence of a
canonical scalar field. After reviewing the basic equations governing the
background cosmology in -gravity, we turn to study the cosmological
perturbations and obtain the evolutionary equations for the scalar and tensor
perturbations. Solving those equations, we find the power spectra for the
scalar and tensor perturbations. Then, we consider a power-law form for the
function in the action and examine the inflationary models with the
power-law and intermediate scale factors. We see that in contrast with the
standard inflationary scenario based on the Einstein gravity, in the considered
-gravity scenario, the power-law and intermediate inflationary models can
be compatible with the observational results of Planck 2015 at 68\% CL. In our
-gravity setting, the potentials responsible for both the power-law and
intermediate inflationary models have the power-law form but the power is different for them. Therefore, we can refine
some of power-law inflationary potentials in the framework of -gravity
while they are disfavored by the observational data in the standard
inflationary scenario. Interestingly enough, the self-interacting quartic
potential which has special reheating properties,
can be consistent with the Planck 2015 data in our -gravity scenario
while it is ruled out in the standard inflationary scenario.Comment: 30 pages, 3 figure
Thermodynamics of apparent horizon in modified FRW universe with power-law corrected entropy
We derive the modified Friedmann equation corresponding to the power-law
corrected entropy-area relation which is motivated by the entanglement of quantum
fields in and out of the apparent horizon. We consider a non-flat modified FRW
universe containing an interacting viscous dark energy with dark matter and
radiation. For the selected model, we study the effect of the power-law
correction term to the entropy on the dynamics of dark energy. Furthermore, we
investigate the validity of the generalized second law (GSL) of gravitational
thermodynamics on the apparent horizon and conclude that the GSL is satisfied
for .Comment: 12 pages, Accepted for Publication in JHE
The generalized second law for the interacting new agegraphic dark energy in a non-flat FRW universe enclosed by the apparent horizon
We investigate the validity of the generalized second law of gravitational
thermodynamics in a non-flat FRW universe containing the interacting new
agegraphic dark energy with cold dark matter. The boundary of the universe is
assumed to be enclosed by the dynamical apparent horizon. We show that for this
model, the equation of state parameter can cross the phantom divide. We also
present that for the selected model under thermal equilibrium with the Hawking
radiation, the generalized second law is always satisfied throughout the
history of the universe. Whereas, the evolution of the entropy of the universe
and apparent horizon, separately, depends on the equation of state parameter of
the interacting new agegraphic dark energy model.Comment: 9 pages, accepted for publication in Int. J. Theor. Phy
Power Law Entropy Corrected New-Agegraphic Dark Energy in Ho\v{r}ava-Lifshitz Cosmology
We investigate the new agegraphic dark energy (NADE) model with power-law
corrected entropy in the framework of Ho\v{r}ava-Lifshitz cosmology. For a
non-flat universe containing the interacting power-law entropy-corrected NADE
(PLECNADE) with dark matter, we obtain the differential equation of the
evolution of density parameter as well as the deceleration parameter. To study
parametric behavior, we used an interesting form of state parameter as function
of redshift . We found that phantom
crossing occurs for the state parameter for a non-zero coupling parameter, thus
supporting interacting dark energy model.Comment: 13 pages, 2 figures, accepted for publication in 'Canadian J. Phys.
On uniquely k-list colorable planar graphs, graphs on surfaces, and regular graphs
A graph is called uniquely k-list colorable (ULC) if there exists a
list of colors on its vertices, say ,
each of size , such that there is a unique proper list coloring of from
this list of colors. A graph is said to have property if it is not
uniquely -list colorable. Mahmoodian and Mahdian characterized all graphs
with property . For property has been studied only for
multipartite graphs. Here we find bounds on for graphs embedded on
surfaces, and obtain new results on planar graphs. We begin a general study of
bounds on for regular graphs, as well as for graphs with varying list
sizes
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