Browsing by Author "Diab, Abdel Magied"

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Black hole corrections due to minimal length and modified dispersion relation
(WORLD SCIENTIFIC PUBL CO PTE LTD, 2015) Tawfik, Abdel Nasser; Diab, Abdel Magied
The generalized uncertainty principles (GUP) and modified dispersion relations (MDR) are much like two faces for one coin in research for the phenomenology of quantum gravity which apparently plays an important role in estimating the possible modifications of the black hole thermodynamics and the Friedmann equations. We first reproduce the horizon area for different types of black holes and investigate the quantum corrections to Bekenstein-Hawking entropy (entropy-area law). Based on this, we study further thermodynamical quantities and accordingly the modified Friedmann equation in four-dimensional de Sitter-Schwarzschild, Reissner-Nordstrom and Garfinkle-Horowitz-Strominger black holes. In doing this, we applied various quantum gravity approaches. The MDR parameter relative to the GUP one is computed and the properties of the black holes are predicted. This should play an important role in estimating response of quantum gravity to the various metric-types of black holes. We found a considerable change in the thermodynamics quantities. We find that the modified entropy of de Sitter-Schwarzshild and Reissner-Nordstrom black holes starts to exist at a finite standard entropy. The Garfinkle-Horowitz-Strominger black hole shows a different entropic property. The modified specific heat due to GUP and MDR approaches vanishes at large standard specific heat, while the corrections due to GUP result in different behaviors. The specific heat of modified de Sitter-Schwarzshild and Reissner-Nordstrom black holes seems to increase, especially at large standard specific heat. In the early case, the black hole cannot exchange heat with the surrounding space. Accordingly, we would predict black hole remnants which may be considered as candidates for dark matter.
Equation of State in Non-Zero Magnetic Field
(IOP PUBLISHING LTD, 2016) Ezzelarab, Nada; Diab, Abdel Magied; Tawfik, Abdel Nasser
The Polyakov linear-sigma model (PLSM) and Hadron Resonance Gas (HRG) model are considered to study the liadronic and partonic equation(s) of state, the pressure, and response to finite magnetic field, the magnetization. The results are compared to recent lattice QCD calculations. Both models are in fairly good agreement with the lattice.
Friedmann inflation in Horava-Lifshitz gravity with a scalar field
(WORLD SCIENTIFIC PUBL CO PTE LTD, 2016) Tawfik, Abdel Nasser; Diab, Abdel Magied; Abou El Dahab, Eiman
We study Friedmann inflation in general Horava-Lifshitz (HL) gravity with detailed and nondetailed and also without the projectability conditions. Accordingly, we derive the modifications in the Friedmann equations due to single scalar field potentials describing power-law and minimal-supersymmetrically extended inflation. By implementing four types of the equations-of-state characterizing the cosmic background geometry, the dependence of the tensorial and spectral density fluctuations and their ratio on the inflation field is determined. The latter characterizes the time evolution of the inflation field relative to the Hubble parameter. Furthermore, the ratio of tensorial-to-spectral density fluctuations is calculated in dependence on the spectral index. The resulting slow-roll parameters apparently differ from the ones deduced from the standard General Relativity (Friedmann gravity). We also observe that the tensorial-to-spectral density fluctuations continuously decrease when moving from nondetailed HL gravity, to Friedmann gravity, to HL gravity without the projectability, and to detailed HL gravity. This regular pattern is valid for three types of cosmic equations-of-state and different inflation potential models. The results fit well with the recent Planck observations.
Our Understanding on Landau-Raychaudhuri Cosmology
(IOP PUBLISHING LTD, 2016) Diab, Abdel Magied; Tawfik, Abdel Nasser
Recent developments to the generalized uncertainty principles (GUPs) and the modified dispersion relations (MDRs) play an important role in estimating the quantum corrections to the cosmic line element. We first apply both approaches to de Sitter-Schwarzschild and Reissner-Nordstrom black holes. Then from the fixed point method, the modified Landau-Raychaudhuri equations are derived in emergent cosmic space. We conclude that (non-)singular big bang solutions are obviously model dependent.
Polyakov SU(3) extended linear-sigma model: Sixteen mesonic states in chiral phase structure
(AMER PHYSICAL SOC, 2015) Tawfik, Abdel Nasser; Diab, Abdel Magied
In the mean field approximation, the derivative of the grand potential, nonstrange and strange condensates, and the deconfinement phase transition in a thermal and dense hadronic medium are verified in the SU(3) Polyakov linear-sigma model (PLSM). The chiral condensates sigma(x) and sigma(y) are analyzed with the goal of determining the chiral phase transition. The temperature and density dependences of the chiral mesonic phase structures are taken as free parameters and fitted experimentally. They are classified according to the scalar meson nonets: (pseudo) scalar and (axial) vector. For the deconfinement phase transition, the effective Polyakov-loop potentials phi and phi* are implemented. The in-medium effects on the masses of sixteen mesonic states are investigated. The results are presented for two different forms for the effective Polyakov-loop potential and compared with other models, which include and exclude the anomalous terms. It is found that the Polyakov-loop potential has considerable effects on the chiral phase transition so that the restoration of the chiral symmetry breaking becomes sharper and faster. Assuming that the Matsubara frequencies contribute to the meson masses, we have normalized all mesonic states with respect to the lowest frequency. By doing this, we characterize temperatures and chemical potentials at which the different meson states dissolve to free quarks. Different dissolving temperatures and chemical potentials are estimated. The different meson states survive the typically averaged QCD phase boundary, which is defined by the QCD critical temperatures at varying chemical potentials. The thermal behavior of all meson masses has been investigated in the large-N-c limit. It is found that, at high T, the scalar meson masses are T independent (except pi and sigma). For the pseudoscalar meson masses, the large-N-c limit unifies the T dependences of the various states into a universal bundle. The same is also observed for axial and axial-vector meson masses.
QCD Thermodynamics and Magnetization in Nonzero Magnetic Field
(HINDAWI LTD, 2016) Tawfik, Abdel Nasser; Diab, Abdel Magied; Ezzelarab, Nada; Shalaby, Asmaa G.
In nonzero magnetic field, the magnetic properties and thermodynamics of the quantum-chromodynamic (QCD) matter are studied in the hadron resonance gas and the Polyakov linear-sigma models and compared with recent lattice calculations. Both models are fairly suited to describe the degrees of freedomin the hadronic phase. The partonic ones are only accessible by the second model. It is found that the QCD matter has paramagnetic properties, which monotonically depend on the temperature and are not affected by the hadron-quark phase transition. Furthermore, raising the magnetic field strength increases the thermodynamic quantities, especially in the hadronic phase, but reduces the critical temperature, that is, inverse magnetic catalysis.
Quark-hadron phase structure, thermodynamics, and magnetization of QCD matter
(IOP PUBLISHING LTD, 2018) Tawfik, Abdel Nasser; Diab, Abdel Magied; Hussein, M. T.
The SU(3) Polyakov linear-sigma model (PLSM) is systematically implemented to characterize the quark-hadron phase structure and to determine various thermodynamic quantities and the magnetization of quantum chromodynamic (QCD) matter. Using mean-field approximation, the dependence of the chiral order parameter on a finite magnetic field is also calculated. Under a wide range of temperatures and magnetic field strengths, various thermodynamic quantities including trace anomaly, speed of sound squared, entropy density, and specific heat are presented, and some magnetic properties are described as well. Where available these results are compared to recent lattice QCD calculations. The temperature dependence of these quantities confirms our previous finding that the transition temperature is reduced with the increase in the magnetic field strength, i.e. QCD matter is characterized by an inverse magnetic catalysis. Furthermore, the temperature dependence of the magnetization showing that QCD matter has paramagnetic properties slightly below and far above the pseudo-critical temperature is confirmed as well. The excellent agreement with recent lattice calculations proves that our QCD-like approach (PLSM) seems to possess the correct degrees of freedom in both the hadronic and partonic phases and describes well the dynamics deriving confined hadrons to deconfined quark-gluon plasma.
SU(3) Polyakov linear-sigma model: Conductivity and viscous properties of QCD matter in thermal medium
(WORLD SCIENTIFIC PUBL CO, 2016) Tawfik, Abdel Nasser; Diab, Abdel Magied; Hussein, M. T.
In mean field approximation, the grand canonical potential of SU(3) Polyakov linear-sigma model (PLSM) is analyzed for chiral phase transition, sigma(l) and sigma(s) and for deconfinement order-parameters, phi and phi* of light- and strange-quarks, respectively. Various PLSM parameters are determined from the assumption of global minimization of the real part of the potential. Then, we have calculated the subtracted condensates (Delta(l), s). All these results are compared with recent lattice QCD simulations. Accordingly, essential PLSM parameters are determined. The modeling of the relaxation time is utilized in estimating the conductivity properties of the QCD matter in thermal medium, namely electric [sigma(el)(T)] and heat [kappa(T)] conductivities. We found that the PLSM results on the electric conductivity and on the specific heat agree well with the available lattice QCD calculations. Also, we have calculated bulk and shear viscosities normalized to the thermal entropy, xi/s and eta/s, respectively, and compared them with recent lattice QCD. Predictions for (xi/s)/(sigma(el)/T) and (eta/s)/(sigma(el)/T) are introduced. We conclude that our results on various transport properties show some essential ingredients, that these properties likely come up with, in studying QCD matter in thermal and dense medium.