arXiv subjects

A. Tawfik

Publications and source records attributed to A. Tawfik.

At least 19 recordsLinked to original sources

arXiv2026

Quantum-Conditioned Curvatures in Spacetime Surrounding Kerr-Newmann Black Hole

This research examines the possibility whether the curvatures found in conventional General Relativity (GR) are the only existing ones, using both analytical and numerical techniques. To this end, we introduce a thorough investigation of Riemann curvatures in the spacetime surrounding a Kerr-Newmann black hole, which is distinguished by its specific electric charges and rotational dynamics. We apply a geometric quantization ansatz that centers on the quantization of the metric tensor, from which the complete set of field equations can be derived. The conformal transformation of the standard metric tensor upholds all the principles of GR while also extending its applicability to lower (quantum) scales. We recognize two types of Riemann curvatures. In addition to the positive curvatures present in classical GR formulations, we also find significant negative curvatures at lower (quantum) scales. This may indicate quantum sources of gravitation that classical GR does not seem equipped to explore.

physics.gen-ph↗

arXiv2026

Stress-Energy Tensor for Modified General Relativity with Quantum-Deformed Metric in Riemann Spacetime

The generalized noncommutative Heisenberg algebra, which is based on the generalized uncertainty principle, imposes a minimal length uncertainty on quantum mechanics (QM), on one hand. On the other hand, the quantum-induced spacetime which is based on quantum-deformed metric through geometric quantization is proposed as additional curvatures on the relativistic tangent bundle on Finsler manifold. An additional term that incorporates minimal length discretization along with second-order derivatives of tangent covectors, thereby suggesting an approach to reconcile the principles of QM with General Relativity (GR), is utilized for the construction of a torsion-free quantum-deformed metric on Riemann manifold. Consequently, it is proposed that quantum-induced revisions to the symmetric stress-energy tensor, source of spacetime curvature, along with the current density related to the gauge transformations of gravity, ought to be taken into account in the matter Lagrangian with electromagnetic and scalar components. Vanishing covariant derivative of the quantum-induced stress-energy tensor suggests that the corresponding continuity equation implies that the gravitational fields do work on the classical and quantum matter and vice versa and the non-gravitational energy and momentum are no longer entirely conserved. For vanishing tangent covector derivatives and/or minimal length uncertainty, the classical formulations of the Einstein stress-energy tensor are retained and accordingly that of GR and QM. We conclude that the proposed quantum-induced formulation of the stress-energy tensor is fundamentally suitable for both classical and quantum-induced field equations.

gr-qc↗

arXiv2025

Vacuum Homogeneous and Nonhomogeneous Metrics with Conventional and Quantized Metric Tensor: Singular or Nonsingular Solution

To investigate whether the Universe underwent a singularity or maintained a nonsingular state, we carry out analytical and numerical analyses of the evolution of the Raychaudhuri equations in vacuum, alongside homogeneous and nonhomogeneous cosmic backgrounds. The results obtained from the Schwarzschild, Friedmann--Lemaitre--Robertson--Walker (FLRW), and Einstein--Gilbert--Straus (EGS) metrics are systematically compared. Analyzing the results from both, conventional and quantized metric tensor, it revealed insights into the nature of initial and spatial singularities. Results associated with the Schwarzschild metric demonstrate a positive evolution that corresponds with a reduction in radial distance (nonsingularity). In contrast, the proposed quantization reverses this trend, leading to a negative evolution (singularity). The situation is similar for the FLRW metric, where the suggested quantization results in a positive evolution as cosmic time decreases, in contrast to the classical and conventional metrics, which are associated with negative evolution. The analysis of the EGS metric reveals that classical evolution remains positively oriented, particularly with a reduction in radial distance. Moreover, the introduction of quantized and conventional metric tensors fully retrains the cosmic time dependence. The results obtained are a rightful recognition of the substantial efforts dedicated to the establishment of the Swiss-cheese model, demonstrating that the EGS metric indeed facilitates the temporal and spatial development of our Universe.

gr-qc↗

arXiv2017

Minimal-supersymmetric extended inflation field in Horava-Lifshitz gravity

We study the Friedmann inflation in general covariant Horava-Lifshitz (HL) gravity without the projectability conditions and with detailed and non-detailed balance conditions. Accordingly, we derive modifications in the Friedmann equations due to a single-scalar field potential describing minimal-supersymmetrically extended inflation. By implementing two time-independent equations of state (EoS) characterizing the cosmic background geometry filled up with dark energy, the dependence of the tensorial and scalar density fluctuations and their ratios on the inflation field are determined. The latter refer to the time evolution of the inflationary field relative to the Hubble parameter. Furthermore, the ratios of tensorial-to-spectral density fluctuations are calculated in dependence on the spectral index. For cold dark energy EoS $ω=-1/3$, we find that the tensorial-to-spectral density fluctuations are not depending on the different theories of gravity and the results are very small relative to the recent BICEP2/Keck Array-Planck observations, $10^{-9} \lessapprox r \lessapprox 10^{-3}$. We have also calculated the tensorial and scalar perturbations of the primordial spectra.

gr-qc↗

arXiv2017

FLRW Cosmology with Horava-Lifshitz Gravity: Impacts of Equations of State

Inspired by Lifshitz theory for quantum critical phenomena in condensed matter, Horava proposed a theory for quantum gravity with an anisotropic scaling in ultraviolet. In Horava-Lifshitz gravity (HLG), we have studied the impacts of six types of equations of state on the evolution of various cosmological parameters such as Hubble parameters and scale factor. From the comparison of the general relativity gravity with the HLG with detailed and without with non-detailed balance conditions, remarkable differences are found. Also, a noticeable dependence of singular and non-singular Big Bang on the equations of state is observed. We conclude that HLG explains various epochs in the early universe and might be able to reproduce the entire cosmic history with and without singular Big Bang.

gr-qc↗

arXiv2016

Possible interrelations among chemical freezeout conditions

At thermal equilibrium, different chemical freezeout conditions have been proposed so far. They have an ultimate aim of proposing a universal description for the chemical freezeout parameters ($T_{ch}$ and $μ_b$), which are to be extracted from the statistical fitting of different particle ratios measured at various collision energies with calculations from thermal models. A systematic comparison between these conditions is presented. The physical meaning of each of them and their sensitivity to the hadron mass cuts are discussed. Based on availability, some of them are compared with recent lattice calculations. We found that most of these conditions are thermodynamically equivalent, especially at small baryon chemical potential. We propose that further crucial consistency tests should be performed at low energies. The fireball thermodynamics is another way of guessing conditions describing the chemical freezeout parameters extracted from high-energy experiments. We endorse the possibility that the various chemical freezeout conditions should be interpreted as different aspects of one universal condition.

hep-ph↗

arXiv2014

Polyakov linear SU(3) sigma model: features of higher order moments in dense and thermal hadronic medium

In order to characterize the higher order moments of the particle multiplicity, we implement the linear-sigma model with Polyakov-loop correction. We first studied the critical phenomena and estimated some thermodynamic quantities. Then, we compared all these results with the first--principle lattice QCD calculations. Then, the extensive study of non-normalized four moments is followed by investigating their thermal and density dependence. We repeat this for moments normalized to temperature and chemical potential. The fluctuations of the second order moment is used to estimate the chiral phase--transition. Then, we implement all these in mapping out the chiral phase transition, which shall be compared with the freeze-out parameters estimated from the lattice QCD simulations and the thermal models are compared with the chiral phase--diagram.

hep-ph↗

arXiv2013

Thermal Description of Particle Production in Au-Au Collisions at STAR Energies

The hadron ratios measured in central Au-Au collisions are analysed by means of Hadron Resonance Gas (HRG) model over a wide range of nucleon-nucleon center-of-mass energies ranging from 7.7 to 200 GeV as offered by the STAR Beam Energy Scan I (BES-I). We restrict the discussion on STAR BES-I, because of large statistics and over all homogeneity of STAR measurements (one detector) against previous experiments. Over the last three decades, various heavy-ion experiments utilizing different detectors (different certainties) have been carried out. Regularities in produced particles at different energies haven been studied. The temperature and baryon chemical potential are deduced from fits of experimental ratios to thermal model calculations assuming chemical equilibrium. We find that the resulting freeze-out parameters using single hard-core value and point-like constituents of HRG are identical. This implies that the excluded-volume comes up with no effect on the extracted parameters. We compare the results with other studies and with the lattice QCD calculations. Various freeze-out conditions are confronted with the resulting data set. The effect of feed-down contribution from week decay and of including new resonances are also analysed. At vanishing chemical potential, a limiting temperature was estimated as T=158.5 MeV with 3 MeV uncertainty.

nucl-th↗

arXiv2013

Some Intensive and Extensive Quantities in High-Energy Collisions

We review the evolution of some statistical and thermodynamical quantities measured in difference sizes of high-energy collisions at different energies. We differentiate between intensive and extensive quantities and discuss the importance of their distinguishability in characterizing possible critical phenomena of nuclear collisions at various energies with different initial conditions.

hep-ph↗

arXiv2013

Constant Trace Anomaly as a Universal Condition for the Chemical Freeze-Out

Finding out universal conditions describing the freeze-out parameters was a subject of various phenomenological studies. In the present work, we introduce a new condition based on constant trace anomaly (or interaction measure) calculated in the hadron resonance gas (HRG) model. Various extensions to the {\it ideal} HRG which are conjectured to take into consideration different types of interactions have been analysed. When comparing HRG thermodynamics to that of lattice quantum chromodynamics, we conclude that the hard-core radii are practically irrelevant, especially when HRG includes all resonances with masses less than $2~$GeV. It is found that the constant trace anomaly (or interaction measure) agrees well with most of previous conditions.

hep-ph↗

arXiv2013

Impacts of Generalized Uncertainty Principle on Black Hole Thermodynamics and Salecker-Wigner Inequalities

We investigate the impacts of Generalized Uncertainty Principle (GUP) proposed by some approaches to quantum gravity such as String Theory and Doubly Special Relativity on black hole thermodynamics and Salecker-Wigner inequalities. Utilizing Heisenberg uncertainty principle, the Hawking temperature, Bekenstein entropy, specific heat, emission rate and decay time are calculated. As the evaporation entirely eats up the black hole mass, the specific heat vanishes and the temperature approaches infinity with an infinite radiation rate. It is found that the GUP approach prevents the black hole from the entire evaporation. It implies the existence of remnants at which the specific heat vanishes. The same role is played by the Heisenberg uncertainty principle in constructing the hydrogen atom. We discuss how the linear GUP approach solves the entire-evaporation-problem. Furthermore, the black hole lifetime can be estimated using another approach; the Salecker-Wigner inequalities. Assuming that the quantum position uncertainty is limited to the minimum wavelength of measuring signal, Wigner second inequality can be obtained. If the spread of quantum clock is limited to some minimum value, then the modified black hole lifetime can be deduced. Based on linear GUP approach, the resulting lifetime difference depends on black hole relative mass and the difference between black hole mass with and without GUP is not negligible.

gr-qc↗

arXiv2013

On the Higher Moments of Particle Multiplicity, Chemical Freeze-Out and QCD Critical Endpoint

We calculate the first six non-normalized moments of particle multiplicity within the framework of the hadron resonance gas model. In terms of the lower order moments and corresponding correlation functions, general expressions of higher order moments are derived. Thermal evolution of the first four normalized moments and their products (ratios) are studied at different chemical potentials μ, so that it is possible to evaluate them at chemical freeze out curve. It is found that a non-monotonic behavior, reflecting the dynamical fluctuation and strong correlation of particles starts to appear from the normalized third order moment. We introduce novel conditions for describing the chemical freeze out curve. Although the hadron resonance gas model does not contain any information on the criticality related to the chiral dynamics and singularity in some physical observables, we are able find out the location of the QCD critical endpoint at $μ\sim 350 $MeV and temperature $T \sim 162 $MeV.

hep-ph↗

arXiv2013

Chemical Freeze-Out and Higher Order Multiplicity Moments

We calculate the non-normalized moments of the particle multiplicity within the framework of the hadron resonance gas (HRG) model. At finite chemical potential $μ$, a non-monotonic behavior is observed in the thermal evolution of third order moment (skewness $S$) and the higher order ones as well. Among others, this observation likely reflects dynamical fluctuations and strong correlations. The signatures of non-monotonicity in the normalized fourth order moment (kurtosis $κ$) and its products get very clear. Based on these findings, we introduce a novel condition characterizing the universal freeze-out curve. The chemical freeze-out parameters $T$ and $μ$ are described by vanishing $κ\, σ^2$ or equivalently $m_4=3\,χ^2$, where $σ$, $χ$ and $m_4$ are the standard deviation, susceptibility and fourth order moment, respectively. The fact that the HRG model is not able to release information about criticality related to the confinement and chiral dynamics should not veil the observations related to the chemical freeze-out. Recent lattice QCD studies strongly advocate the main conclusion of the present paper.

hep-ph↗

arXiv2013

Calibrated Fair Measures of Measure: Indices to Quantify an Individual's Scientific Research Output

Are existing ways of measuring scientific quality reflecting disadvantages of not being part of giant collaborations? How could possible discrimination be avoided? We propose indices defined for each discipline (subfield) and which count the plausible contributions added up by collaborators maintaining the spirit of interdependency. Based on the growing debate about defining potential biases and detecting unethical behavior, a standardized method to measure contributions of the astronomical number of coauthors is introduced.

cs.DL↗

arXiv2013

Effects of quantum gravity on the inflationary parameters and thermodynamics of the early universe

The effects of generalized uncertainty principle (GUP) on the inflationary dynamics and the thermodynamics of the early universe are studied. Using the GUP approach, the tensorial and scalar density fluctuations in the inflation era are evaluated and compared with the standard case. We find a good agreement with the Wilkinson Microwave Anisotropy Probe data. Assuming that a quantum gas of scalar particles is confined within a thin layer near the apparent horizon of the Friedmann-Lemaitre-Robertson-Walker universe which satisfies the boundary condition, the number and entropy densities and the free energy arising form the quantum states are calculated using the GUP approach. A qualitative estimation for effects of the quantum gravity on all these thermodynamic quantities is introduced.

gr-qc↗

arXiv2013

Modified Newton's Law of Gravitation Due to Minimal Length in Quantum Gravity

A recent theory about the origin of the gravity suggests that the gravity is originally an entropic force. In this work, we discuss the effects of generalized uncertainty principle (GUP) which is proposed by some approaches to quantum gravity such as string theory, black hole physics and doubly special relativity theories (DSR), on the area law of the entropy. This leads to a $\sqrt{Area}$-type correction to the area law of entropy which imply that the number of bits $N$ is modified. Therefore, we obtain a modified Newton's law of gravitation. Surprisingly, this modification agrees with different sign with the prediction of Randall-Sundrum II model which contains one uncompactified extra dimension. Furthermore, such modification may have observable consequences at length scales much larger than the Planck scale.

gr-qc↗

arXiv2013

Effects of the Generalized Uncertainty Principle on Compact Stars

Based on the generalized uncertainty principle (GUP), proposed by some approaches to quantum gravity such as string theory and doubly special relativity theories, we investigate the effect of GUP on the thermodynamic properties of compact stars with two different components. We note that the existence of quantum gravity correction tends to resist the collapse of stars if the GUP parameter $α$ is taking values between Planck scale and electroweak scale. Comparing with approaches, it is found that the radii of compact stars are found smaller. Increasing energy almost exponentially decreases the radii of compact stars.

gr-qc↗

arXiv2013

Comment on "Investigation of Hadron Multiplicity and Hadron Yield Ratios in Heavy-Ion Collisions"

Oliinychenko, Bugaev and Sorin [arXiv:1204.0103 [hep-ph]] considered the role of conservation laws in discussing possible weaknesses of thermal models which are utilized in describing the hadron multiplicities measured in central nucleus-nucleus collisions. They argued to analyse the criteria for chemical freeze-out and to conclude that none of them were robust. Based on this, they suggested a new chemical freeze-out criterion. They assigned to the entropy per hadron the ad hoc value 7.18 and supposed to remain unchanged over the whole range of the baryo-chemical potentials. Due to unawareness of recent literature, the constant entropy per hadron has been discussed in Ref. [Fizika B18 (2009) 141-150, Europhys.Lett. 75 (2006) 420]. Furthermore, it has been shown that the constant entropy per hadron is equivalent to constant entropy normalized to cubic temperature, an earlier criterion for the chemical freeze-out introduced in Ref. [Europhys.Lett. 75 (2006) 420, Nucl.Phys.A764 (2006) 387-392]. In this comment, we list out the ignored literature, compare between the entropy-number density ratio and two criteria of averaged energy per averaged particle number and constant entropy per cubic temperature. All these criteria are confronted to the experimental results. The physics of constant entropy per number density is elaborated. It is concluded that this ratio can't remain constant, especially at large chemical potential related to AGS and SIS energies.

nucl-th↗