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M. Hashemi

Publications and source records attributed to M. Hashemi.

8 recordsLinked to original sources
arXiv2020

Estimation of the Total Mass of 10 Exoplanets and their Host Stars Based on the Primary Transit Method

In this study, ten exoplanets were studied. Their photometric observations were obtained from the ETD. After performing the data reduction steps, their parameters were obtained through Exofast online software. Then the total mass of the exoplanets and the host stars were obtained through a software that was mentioned in this study. The location of the host stars in this study was also plotted in the H-R diagram.

astro-ph.EP↗
arXiv2018

Emergent Cosmos in Einstein-Cartan Theory

Based on the Padmanabhan's proposal, the accelerated expansion of the universe can be driven by the difference between the surface and bulk degrees of freedom in a region of space, described by the relation $dV/dt=N_{sur}-N_{bulk}$ where $N_{sur}$ and $N_{bulk}=-N_{em}+N_{de}$ are the degrees of freedom assigned to the surface area and the matter-energy content inside the bulk such that the indexes $"em"$ and $"de"$ represent energy-momentum and dark energy, respectively. In the present work, the dynamical effect of the Weyssenhoff perfect fluid with intrinsic spin and its corresponding spin degrees of freedom in the framework of Einstein-Cartan (EC) theory are investigated. Based on the modification of Friedmann equations due to the spin-spin interactions, a correction term for the Padmanabhan's original relation $dV/dt=N_{sur}+N_{em}-N_{de}$ including the number of degrees of freedom related to this spin interactions is obtained through the modification in $N_{bulk}$ term as $N_{bulk}=-N_{em}+N_{spin}+N_{de}$ leading to $dV /d t=N_{sur}+N_{em}-N_{spin} -N_{de}$ in which $N_{spin}$ is the corresponding degrees of freedom related to the intrinsic spin of the matter content of the universe. Moreover, the validity of the unified first law and the generalized second law of thermodynamics for the Einstein-Cartan cosmos are investigated. Finally, by considering the covariant entropy conjecture and the bound resulting from the emergent scenario, a total entropy bound is obtained. Using this bound, it is shown that the for the universe as an expanding thermodynamical system, the total effective Komar energy never exceeds the square of the expansion rate with a factor of $\frac{3}{4π}$.

gr-qc↗
arXiv2015

The laws of thermodynamics and information for emergent cosmology

The aim here is to provide a set of equations for cosmology in terms of information and thermodynamical parameters. The method we implement in order to describe the universe is a development of Padmanabhan\rq{}s approach which is based on the fact that emergence of the cosmic space is provided by the evolution of the cosmic time. In this line we obtain the Friedmann equation or its equivalent the conservation law in terms of information by the implementation of Laundauer\rq{}s principle or in other words the information loss/production rate. Hence, a self consistent description of the universe is provided in terms of thermodynamical parameters. This is due to the fact that in this work the role of information which is the most important actor of all times, has stepped in to cosmology. We provide a picture of the emergent cosmology merely based on the information theory. In addition, we introduce a novel entropy on the horizon, which can also generalize Bekenstein-Hawking entropy for the asymptotic holographic principle.

gr-qc↗
arXiv2015

Hawking temperature and the emergent cosmic space

The aim of this work is to model the evolution of the cosmic space based on thermodynamical parameters. The universe is considered to have an apparent horizon radius with a Kodama-Hayward temperature assigned to it. The method is founded on the fact proposed by Padmanabhan [1,2] that the subtraction of the surface and bulk degrees of freedom provides information on the cosmic space emergence. The fact of the matter is that in this approach the Raychaudhuri equation could even be obtained by the consideration of only thermodynamical parameters. As such, the standard general relativity is taken as the starting point where by implementing the standard cosmological equations we obtain a generalized evolutionary equation supporting emergence of the cosmic space. The method proposed in this work would provide basis for other cosmological models to have an emergent perspective.

gr-qc↗
arXiv2013

Axisymmetric thermoelectroelastic analysis of a piezoelectric half-space

In this study, an analytical solution is presented for thermo-electro-elastic analysis of piezoelectric semi-infinite bodies. For this purpose, governing equations are derived for a transversely isotropic piezoelectric material under axisymmetric thermo-electro-mechanical loading condition. A general closed form analytical solution is presented for the complementary and particular parts of the components of displacement vector and also electric potential function. Then, boundary conditions are imposed and in that case an explicit solution is obtained for piezoelectric semi-infinite bodies. Results show that when a piezoelectric half-space is subjected to constant/ramp surface thermal loading the maximum absolute value of radial stress occurs at the surface of the body. Whereas, the maximum absolute value of stress in normal direction of the half-space surface occurs not on the surface but somewhere near the surface of the body. Moreover, the peak values for these stress curves in the case of combined loadings are closest to the half space surface and the farthest in the case of ramp decaying thermal loading. In contrast to the constant/ramp surface thermal loading no clear maximum point for electric field distribution for the case of combined loadings can be seen in the normal direction to the half-space boundary.

cond-mat.mtrl-sci↗
arXiv2008

Charged Higgs Bosons in the MSSM at CMS: Discovery Reach and Parameter Dependence

The search for MSSM Higgs bosons will be an important goal at the LHC. In order to analyze the search reach of the CMS experiment for the charged MSSM Higgs bosons, we combine the latest results for the CMS experimental sensitivities based on full simulation studies with state-of-the-art theoretical predictions of MSSM Higgs-boson production and decay properties. The experimental analyses are done assuming an integrated luminosity of 30 fb^-1 for the two cases M_H+- < m_t and M_H+- > m_t. The results are interpreted as 5 sigma discovery contours in M_H+- - tan_beta planes of the MSSM for various benchmark scenarios. We study the dependence of the 5 sigma contours on the variation of the relevant SUSY parameters. Particular emphasis is put on analyzing the variation of the discovery contours with the Higgs mixing parameter mu. The variation of mu can shift the prospective discovery reach in tan_beta by up to Delta tan_beta = 40.

hep-ph↗
arXiv2006

Search for the Light Charged Higgs in CMS

In this report the CMS potential for the light charged Higgs boson discovery in the Minimal Supersymmetric Standard Model is presented. First the latest results of the Tevatron and LEP experiments on the light charged Higgs search are reminded. In the rest of the report the perspectives of CMS for the light charged Higgs search are presented with description of some details of the analysis. The results are based on the full simulation and reconstruction of the CMS detector including the systematic uncertainties on the background determination. Finally the $\rm 5σ$ discovery contour for an integrated luminosity of $\rm 30fb^{-1}$ is shown.

hep-ph↗