Browsing by Author "Ezzelarab, Nada"

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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.
Mass fractions in stellar interior during presupernova evolution
(SPRINGER, 2016) Nabi, Jameel; Ezzelarab, Nada
We assume nuclear statistical equilibrium (NSE) conditions and use Saha Equation to calculate mass fractions in stellar interior during presupernova evolution of massive stars. Our ensemble contains 728 nuclei. The distinguishing feature of our calculation is a state-by-state summation of nuclear level densities up to 10 MeV for all nuclei considered in our ensemble. This leads to a more realistic description of nuclear partition function which poses one of the largest uncertainties in the mass fraction calculations under conditions of NSE. The Coulomb correction term was taken into account for the calculation of ground-state binding energies of the nucleons. Our calculated mass fractions are up to four orders of magnitude smaller than previous calculation. The current calculation could prove useful for study of stellar matter during presupernova phases of massive stars.
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.
Temperature-dependent nuclear partition functions and abundances in the stellar interior
(IOP PUBLISHING LTD, 2016-05) Khan, Ali Abas; Ezzelarab, Nada; Tawfik, Abdel Nasser; Nabi, Jameel-Un
We calculate the temperature-dependent nuclear partition functions (TDNPFs) and nuclear abundances for 728 nuclei, assuming nuclear statistical equilibrium (NSE). The theories of stellar evolution support NSE. Discrete nuclear energy levels have been calculated microscopically, using the pn-QRPA theory, up to an excitation energy of 10 MeV in the calculation of the TDNPFs. This feature of our paper distinguishes it from previous calculations. Experimental data is also incorporated wherever available to ensure the reliability of our results. Beyond 10 MeV, we employ a simple Fermi gas model and perform integration over the nuclear level densities to approximate the TDNPFs. We calculate nuclidic abundances, using the Saha equation, as a function of three parameters: stellar density, stellar temperature and the lepton-to-baryon content of stellar matter. All these physical parameters are considered to be extremely important in the stellar interior. The results obtained in this paper show that the equilibrium configuration of nuclei remains unaltered by increasing the stellar density (only the calculated nuclear abundances increase by roughly the same order of magnitude). Increasing the stellar temperature smoothes the equilibrium configuration showing peaks at the neutron-number magic nuclei.