Browsing by Author "Tawfik, Abdel Nasser"

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Analogy of QCD hadronization and Hawking-Unruh radiation at NICA
(SPRINGER, 2016) Tawfik, Abdel Nasser
The proposed analogy of particle production from high-energy collisions and Hawking-Unruh radiation from black holes is extended to finite density (collisions) and finite electric charge (black holes). Assuming that the electric charge is directly proportional to the density (or the chemical potential), it becomes clear that for at least two freezeout conditions; constant s/T-3 and E/N, the proposed analogy works very well. Dependence of radiation (freezeout) temperature on finite electric charge leads to an excellent estimation for kaon-to-pion ratio, for instance, especially in the energy range covered by NICA. The precise and complete measurements for various light-flavored particle yields and ratios are essential in characterizing Hawing-Unruh radiation from charged black holes and the QCD hadronization at finite density, as wel
Axiomatic nonextensive statistics at NICA energies
(Springer, 8/23/2016) Tawfik, Abdel Nasser
We discuss the possibility of implementing axiomatic nonextensive statistics, where it is conjectured that the phase-space volume determines the (non) extensive entropy, on the particle production at NICA energies. Both Boltzmann-Gibbs and Tsallis statistics are very special cases of this generic (non) extensivity. We conclude that the lattice thermodynamics is ab initio extensive and additive and thus the nonextensive approaches including Tsallis statistics categorically are not matching with them, while the particle production, for instance the particle ratios at various center-of-mass energies, is likely a nonextensive process but certainly not of Tsallis type. The resulting freezeout parameters, the temperature and the chemical potentials, are approximately compatible with the ones deduced from Boltzmann-Gibbs statistics.
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.
Chemical freeze-out in Hawking-Unruh radiation and quark-hadron transition
(AMER PHYSICAL SOC, 2015) Tawfik, Abdel Nasser; Yassin, Hayam; Elyazeed, Eman R. Abo
The proposed analogy between hadron production in high-energy collisions and Hawking-Unruh radiation process in the black holes shall be extended. This mechanism provides a theoretical basis for the freeze-out parameters, the temperature (T), and the baryon chemical potential (mu), characterizing the final state of particle production. The results from charged black holes, in which the electric charge is related to mu, are found comparable with the phenomenologically deduced parameters from the ratios of various particle species and the higher-order moments of net-proton multiplicity in thermal statistical models and Polyakov linear-sigma model. Furthermore, the resulting freeze-out condition < E > / < N > similar or equal to 1 GeV for average energy per particle is in good agreement with the hadronization process in the high-energy experiments. For the entropy density (s), the freeze-out condition s/T-3 similar or equal to 7 is found at mu less than or similar to 0.3 GeV. Then, due to the dependence of T on mu, the values of s/T-3 increase with increasing mu. In accordance with this observation, we found that the entropy density (s) remains constant with increasing mu. Thus, we conclude that almost no information is going lost through Hawking-Unruh radiation from charged black holes. It is worthwhile to highlight that the freeze-out temperature from charged black holes is determined independent on both freeze-out conditions.
Corrections to entropy and thermodynamics of charged black hole using generalized uncertainty principle
(WORLD SCIENTIFIC PUBL CO PTE LTD, 2015) Tawfik, Abdel Nasser; AbouEl Dahab, Eiman
Recently, there has been much attention devoted to resolving the quantum corrections to the Bekenstein-Hawking (black hole) entropy, which relates the entropy to the cross-sectional area of the black hole horizon. Using generalized uncertainty principle (GUP), corrections to the geometric entropy and thermodynamics of black hole will be introduced. The impact of GUP on the entropy near the horizon of three types of black holes: Schwarzschild, Garfinkle-Horowitz-Strominger and Reissner-Nordstrom is determined. It is found that the logarithmic divergence in the entropy-area relation turns to be positive. The entropy S, which is assumed to be related to horizon's two-dimensional area, gets an additional terms, for instance 2 root pi alpha root S, where alpha is the GUP parameter.
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.
An estimate of the thermodynamic pressure in high-energy collisions
(WORLD SCIENTIFIC PUBL CO PTE LTD, 2015) Tawfik, Abdel Nasser
We introduce a novel approach to estimate the thermodynamic pressure from heavy-ion collisions based on recently measured higher-order moments of particle multiplicities by the STAR experiment. We start with fitting the experimental results in the most-central collisions. Then, we integrate them back to lower ones. For example, we find that the first-order moment, the mean multiplicity, is exactly reproduced from the integral of variance, the second-order moment. Therefore, the zeroth-order moment, the thermodynamic pressure, can be estimated from the integral of the mean multiplicity. The possible comparison between such a kind of pressure (deduced from the integral of particle multiplicity) and the lattice pressure and the relating of Bjorken energy density to the lattice energy density are depending on lattice QCD at finite baryon chemical potential and first-principle estimation of the formation time of the quark-gluon plasma (QGP).
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.
Hadronic equation of state and speed of sound in thermal and dense medium
(WORLD SCIENTIFIC PUBL CO PTE LTD, 2014) Tawfik, Abdel Nasser; Magdy, Hend
The equation of state p(epsilon) and speed of sound squared c(s)(2) are studied in grand canonical ensemble of all hadron resonances having masses <= 2 GeV. This large ensemble is divided into strange and non-strange hadron resonances and furthermore to pionic, bosonic and fermionic sectors. It is found that the pions represent the main contributors to c(s)(2) and other thermodynamic quantities including the equation of state p(epsilon) at low temperatures. At high temperatures, the main contributions are added in by the massive hadron resonances. The speed of sound squared can be calculated from the derivative of pressure with respect to the energy density, partial derivative p/partial derivative epsilon, or from the entropy-specific heat ratio, s/c(v). It is concluded that the physics of these two expressions is not necessarily identical. They are distinguishable below and above the critical temperature T-c. This behavior is observed at vanishing and finite chemical potential. At high temperatures, both expressions get very close to each other and both of them approach the asymptotic value, 1/3. In the hadron resonance gas (HRG) results, which are only valid below T-c, the difference decreases with increasing the temperature and almost vanishes near T-c. It is concluded that the HRG model can very well reproduce the results of the lattice quantum chromodynamics (QCD) of partial derivative p/partial derivative epsilon and s/c(v), especially at finite chemical potential. In light of this, energy fluctuations and other collective phenomena associated with the specific heat might be present in the HRG model. At fixed temperatures, it is found that c(s)(2) is not sensitive to the chemical potential.
Nuclear inputs of key iron isotopes for core-collapse modeling and simulation
(IOP PUBLISHING LTD, 2014) Nabi, Jameel-Un; Tawfik, Abdel Nasser
From the modeling and simulation results of presupernova evolution of massive stars, it was found that isotopes of iron, Fe54-56, play a significant role inside the stellar cores, primarily decreasing the electron-to-baryon ratio (Y-e) mainly via electron capture processes thereby reducing the pressure support. The neutrinos produced as a result of these capture processes are transparent to the stellar matter and assist in cooling the core, thereby reducing the entropy. The structure of the presupernova star is altered both by the changes in Y-e and the entropy of the core material. Here we present the microscopic calculation of Gamow-Teller strength distributions for isotopes of iron. The calculation is also compared with other theoretical models and experimental data. Presented also are stellar electron capture rates and associated neutrino cooling rates, due to isotopes of iron, in a form suitable for simulation and modeling codes. It is hoped that the nuclear inputs presented here should assist core-collapse simulators in the process of fine-tuning of the Y-e parameter during various phases of presupernova evolution of massive stars. A reliable and accurate time evolution of this parameter is a possible key to generate a successful explosion in modeling of core-collapse supernovae.
On Dynamical Net-Charge Fluctuations within a Hadron Resonance Gas Approach
(HINDAWI LTD, 2016) Tawfik, Abdel Nasser; Abou-, Salem; Shalaby, Asmaa; Hanafy, M
The dynamical net-charge fluctuations (gamma(dyn)) in different particle ratios K/pi, K/p, and p/pi are calculated from the hadron resonance gas (HRG) model and compared with STAR central Au+Au collisions at root s(NN) = 7.7-200 GeV and NA49 central Pb+Pb collisions at root s(NN) = 6.3-17.3 GeV. The three charged particle ratios (K/pi, K/p, and p/pi) are determined as total and average of opposite and average of the same charges. We find an excellent agreement between the HRG calculations and the experimental measurements, especially from STAR beam energy scan (BES) program, while the strange particles in the NA49 experiment at lower Super Proton Synchrotron (SPS) energies are not reproduced by the HRG approach. We conclude that the utilized HRG version seems to take into consideration various types of correlations including strong interactions through the heavy resonances and their decays especially at BES energies.
On SU(3) Effective Models and Chiral Phase Transition
(HINDAWI LTD, 2015) Tawfik, Abdel Nasser; Magdy, Niseem
Sensitivity of Polyakov Nambu-Jona-Lasinio (PNJL) model and Polyakov linear sigma-model (PLSM) has been utilized in studying QCD phase-diagram. From quasi-particle model (QPM) a gluonic sector is integrated into LSM. The hadron resonance gas (HRG) model is used in calculating the thermal and dense dependence of quark-antiquark condensate. We review these four models with respect to their descriptions for the chiral phase transition. We analyze the chiral order parameter, normalized net-strange condensate, and chiral phase-diagram and compare the results with recent lattice calculations. We find that PLSM chiral boundary is located in upper band of the lattice QCD calculations and agree well with the freeze-out results deduced from various high-energy experiments and thermal models. Also, we find that the chiral temperature calculated from HRG is larger than that from PLSM. This is also larger than the freeze-out temperatures calculated in lattice QCD and deduced from experiments and thermal models. The corresponding temperature and chemical potential are very similar to that of PLSM. Although the results from PNJL and QLSM keep the same behavior, their chiral temperature is higher than that of PLSM and HRG. This might be interpreted due the very heavy quark masses implemented in both models.
On thermodynamic self-consistency of generic axiomatic-nonextensive statistics
(IOP PUBLISHING LTD, 2017-05) Abo Elyazeed, Eman R.; Yassin, Hayam; Tawfik, Abdel Nasser
Generic axiomatic-nonextensive statistics introduces two asymptotic properties, to each of which a scaling function is assigned. The first and second scaling properties are characterized by the exponents c and d, respectively. In the thermodynamic limit, a grand -canonical ensemble can be formulated. The thermodynamic properties of a relativistic ideal gas of hadron resonances are studied, analytically. It is found that this generic statistics satisfies the requirements of the equilibrium thermodynamics. Essential aspects of the thermodynamic self-consistency are clarified. Analytical expressions are proposed for the statistical fits of various transverse momentum distributions measured in most-central collisions at different collision energies and colliding systems. Estimations for the freezeout temperature (T-ch) and the baryon chemical potential (mu(b)) and the exponents c and d are determined. The earlier are found compatible with the parameters deduced from Boltzmann-Gibbs (BG) statistics (extensive), while the latter refer to generic nonextensivities. The resulting equivalence class (c, d) is associated with stretched exponentials, where Lambert function reaches its asymptotic stability. In some measurements, the resulting nonextensive entropy is linearly composed on extensive entropies. Apart from power-scaling, the particle ratios and yields are excellent quantities to highlighting whether the particle production takes place (non)extensively. Various particle ratios and yields measured by the STAR experiment in central collisions at 200, 62.4 and 7.7 GeV are fitted with this novel approach. We found that both c and d < 1, i.e. referring to neither BG-nor Tsallis-type statistics, but to (c, d) entropy, where Lambert functions exponentially rise. The freezeout temperature and baryon chemical potential are found comparable with the ones deduced from BG statistics (extensive). We conclude that the particle production at STAR energies is likely a nonextensive process but not necessarily BG or Tsallis type.
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.
Particle production and chemical freezeout from the hybrid UrQMD approach at NICA energies
(Springer, 10/26/2016) Scheinast, Werner; Rogachevsky, Oleg; Sorin, Alexander; Hanafy, Mahmoud; Shalaby, Asmaa G; Abou-Salem, Loutfy I; Tawfik, Abdel Nasser
The energy dependence of various particle ratios is calculated within the Ultra-relativistic Quantum Molecular Dynamics approach and compared with the hadron resonance gas (HRG) model and measurements from various experiments, including RHIC-BES, SPS and AGS. It is found that the UrQMD particle ratios agree well with the experimental results at the RHIC-BES energies. Thus, we have utilized UrQMD in simulating particle ratios at other beam energies down to 3GeV, which will be accessed at NICA and FAIR future facilities. We observe that the particle ratios for crossover and first-order phase transition, implemented in the hybrid UrQMD v3.4, are nearly indistinguishable, especially at low energies (at large baryon chemical potentials or high density).
Phenomenology of light- and strange-quark simultaneous production at high energies
(PLEIADES PUBLISHING INC, 2017-11) Elyazeed, Eman R. Abo; Yassin, Hayam; Tawfik, Abdel Nasser
This letter presents an extension of EPL116(2017) 62001 to light- and strange-quark nonequilibrium chemical phase-space occupancy factors (gamma(q,s)). The resulting damped trigonometric functionalities relating gamma(q,s) to the nucleon-nucleon center-of-mass energies (root s(NN)) looks very similar except different coefficients. The phenomenology of the resulting gamma(q,s) (root s(NN)) describes a rapid decrease at root s(NN) less than or similar to 7 GeV followed by a faster increase up to similar to 20 GeV. Then, both gamma(q,s) become nonsensitive to root s(NN). Although these differ from gamma(s) (root s(NN)) obtained at gamma(q) (root s(NN)) = 1, various particle ratios including K+/pi(+), K-/pi(-), Lambda/pi(-), (Lambda) over bar/pi(-), Xi(+)/pi(+), and Omega/pi(-), can well be reproduced, as well. We conclude that gamma(q,s) (root s(NN)) should be instead determined from fits of various particle yields and ratios but not merely from fits to the particle ratio k(+)/pi(+).
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.
Review on Dark Energy Models
(MAIK NAUKA/INTERPERIODICA/SPRINGER, 2019-04) Tawfik, Abdel Nasser; Abou El Dahab, Eiman
Based on quantum mechanics and general relativity, Karolyhazy proposed a generalization to the well-known Heisenberg uncertainty relation in which the energy density of quantum fluctuations of space-time plays a crucial role. Later on, various holographic DE models were suggested, in which the Hubble scale (size) and the age of the universe were assumed as measures for the largest infrared cutoff satisfying the holographic principle and energy bounds assuring applicability of quantum field theory. We review various models based on the holographic principle and the Karolyhazy relation and compare these to the space-time foam and superconducting DE models. We analyze their (in)stability against cosmological perturbation.