arXiv subjects

Nazek Alessa

Publications and source records attributed to Nazek Alessa.

8 recordsLinked to original sources

arXiv2026

Probing Primordial Cosmology Through BBN Observational Constraints Under Extended Gravitational Dynamics

In this article, We investigate the cosmological consequences of a recently developed $f(R,G,\mathcal{T})$ gravitational framework, in which the action is formulated as a general function of the Ricci scalar $R$, the Gauss-Bonnet invariant $G$, and the trace of the energy-momentum tensor $\mathcal{T}$. As one of the most reliable probes of the physical conditions in the early universe, Big Bang nucleosynthesis offers a stringent framework for testing deviations from standard cosmology. We consider four representative models that are analyzed and constrained using observational limits on $\left|\Delta T_f/T_f\right|$ and the primordial helium mass fraction $Y_p$. The bounds obtained identify the allowed parameter regions for each model and demonstrate that significant departures from standard cosmology are compatible with nucleosynthesis observations. Our analysis shows that broad regions of the parameter space satisfy existing nucleosynthesis constraints, indicating the consistency of $f(R,G,\mathcal{T})$ gravity with the observed primordial light-element abundances and the established picture of the early universe preserving the observed abundances of light nuclei.

gr-qc↗

arXiv2026

Probing f(R) AdS Black Hole via Hawking Evaporation, Shadows and Thermal Fluctuations

The process of Hawking evaporation, shadows and thermal fluctuations are investigated within the fabric of f(R) AdS Black Hole (BH). Specifically, the Hawking evaporation process is analyzed numerically using the Stefan-Boltzmann law. The results indicate that the BH lifetime is always infinite, which means the BH becomes a remnant in the late time. Additionally, the evaporation rate depends on the AdS radius and coupling parameters. We further examined the visual properties of BH shadows observed for various values of the two parameters. The results reveal that the BH shadow radius decreases with $\psi_{0}$, while it increases with $\lambda$. Consequently, we further investigate the infalling accretion matter in the vicinity of BHs. The results depict that while variations in relevant parameters do influence the central region, the important factor is the change in optical appearance of the bright photon ring, which is exhibited at the position of the photon sphere. Next, we discuss many thermodynamical quantities, such as temperature, entropy, Helmholtz free energy, internal energy, corrected pressure, enthalpy, Gibbs free energy and specific heat and interpret how the variations in $\lambda$ and $\psi_{0}$ impact on the stability and phase transitions of the AdS BHs.

gr-qc↗

arXiv2026

Imprints of Black Hole Shadows and Polarization Patterns of Various Thick Disks: Bumblebee gravity

The main objective of this study is to explore the shadow and polarization patterns of a Kerr-Sen-like BH induced from Bumblebee gravity, which, among other alternative theories of gravity beyond Einstein gravity, stands out as a promising candidate for explaining certain high-energy astrophysical phenomena. Specifically, we would like to probe the influence of the rate of LSB parameter $\ell$ and the Bumblebee charge $Q$ on the resulting image morphology at $230\mathrm{GHz}$. We adopt a phenomenological RIAF-like model and an analytical BAAF disk model. Both models depict that the bright ring is encircled by two central dark regions, each of which gradually shrinks with increasing $\ell$. Consequently, frame-dragging gives rise to a pronounced brightness asymmetry, which is more enhanced with increasing $Q$. A notable feature in the anisotropic emission case is the emergence of a vertically stretched, elliptical ring structure. Compared with the RIAF framework, the bright ring in the BAAF disk images appears geometrically thinner, and the separation between the primary and higher-order images becomes more pronounced. Finally, the polarization patterns trace the brightness distribution and vary with both $\ell$ and $Q$, reflecting the spacetime structure. These results demonstrate that intensity and polarization in thick disk models provide probes of Kerr-Sen-like BHs and near-horizon accretion physics

gr-qc↗

arXiv2026

Characterizing quantum correlations and quantum teleportation in $gg \to t\bar{t}$ and $q\bar{q} \to t\bar{t}$ processes under noisy channels

The measurement of top-quark spin correlations provides a key tool for probing its interactions with high precision. Owing to its extremely short lifetime ($\tau \sim 10^{-25}$ s), the top quark preserves its spin polarization information, making the $t\bar{t}$ system an ideal framework for investigating quantum correlations in high-energy physics. In this work, we analyze quantum correlations in $t\bar{t}$ pairs produced in QCD using several quantum information-theoretic measures, including Bell nonlocality, quantum steering, concurrence, and geometric quantum discord. Their dependence on kinematic variables is examined in both the $gg \to t\bar{t}$ and $q\bar{q} \to t\bar{t}$ channels, with convergence toward the $gg \to t\bar{t}$ dominated regime in the ultra-relativistic limit ($\beta = 1$). We also investigate the effect of three effective decoherence channels (AD, PD, and PF). The AD and PD channels lead to a monotonic degradation of correlations as the decoherence parameter $p$ increases, while the PF channel exhibits a symmetric behavior around $p=1/2$. The impact of these channels on quantum teleportation is analyzed, showing that it remains above the classical threshold of $2/3$ even in the presence of noise. These results indicate that certain quantum resources can persist despite decoherence, opening new perspectives at the interface of quantum information and particle physics.

quant-ph↗

arXiv2026

Dephasing Effects on the Dynamical Evolution of Quantum Correlations and Coherence in Neutrino Oscillations

Neutrino oscillations confirm the presence of mode entanglement, as each flavor eigenstate is composed of a coherent superposition of distinct mass eigenstates. In this work, we investigate the dynamics of quantum resources in neutrino oscillation systems by analyzing quantum steering, logarithmic negativity, and quantum coherence within a two-flavor framework. Treating neutrino oscillations as an effective two-level quantum system, we study the influence of environmental decoherence on these nonclassical features by modeling the system as an open quantum system. Three representative noise channels are considered, namely amplitude damping (AD), phase flip (PF), and phase damping (PD), allowing us to capture both dissipative and dephasing mechanisms. We examine the evolution of quantum resources in both Markovian and non-Markovian regimes, highlighting the role of memory effects in the system-environment interaction. The results reveal a clear hierarchy in the robustness of quantum resources under decoherence. Steering is the most sensitive correlation in the hierarchy under decoherence effects. while logarithmic negativity exhibits intermediate robustness. Quantum coherence displays the highest resilience, persisting over a wider range of parameters. In the PF and PD channels, logarithmic negativity and coherence are shown to exhibit identical dynamical behavior, reflecting their common dependence on phase-related noise. In contrast, the non-Markovian regime leads to delayed decoherence and partial revivals of entanglement and coherence due to information backflow, whereas quantum steering remains strongly suppressed. These findings provide a comparison of different quantum resources in neutrino oscillation systems and offer new insights into the interplay between decoherence mechanisms and quantum correlations.

quant-ph↗

arXiv2026

Mass-correction-induced enhancement of quantum correlations even beyond entanglement in the $e^{+}e^{-} \rightarrow J/\psi \rightarrow \Lambda(p\pi^{-}) \bar{\Lambda}(\bar{p}\pi^{+})$ process at the BESIII experiment under memory effects

In this work, we derive the bipartite density matrix for the $e^{+}e^{-} \rightarrow J/\psi \rightarrow \Lambda(p\pi^{-}) \bar{\Lambda}(\bar{p}\pi^{+})$ process at BESIII. We evaluate the impact of mass corrections and memory effects (within Markovian and non-Markovian regimes) on quantum correlations even beyond entanglement. The dependence of these quantum properties on the scattering angle $\varphi$ is analyzed, with a particular focus on the impact of mass corrections. By comparing massless and mass-corrected scenarios, we demonstrate that the inclusion of mass effects enhances the maximum violation of the Bell inequality. While the qualitative temporal behavior remains unchanged, mass corrections quantitatively modify the angular distribution and introduce additional extrema at $\varphi=0$ and $\varphi=\pi$, thereby strengthening non-local correlations without altering their fundamental dynamical origin. An examination of the hierarchy of quantum correlations in baryon-antibaryon systems yields partial confirmation: $\text{Bell Nonlocality} \subset \text{Steering} \subset \text{Entanglement} \subset \text{Discord}$. Additionally, our results show that classical correlations serve to mitigate the decoherence and the decay of quantum correlations. This interplay between classical and quantum correlations suggests practical applications in quantum information and provides a robust framework for investigating baryon-antibaryon interactions.

quant-ph↗

arXiv2025

Orthogonal splitting of the Riemann curvature tensor and its implications in modeling compact stellar structures

Although the interpretation of complexity in extended theories of gravity is available in the literature, its illustration in $f(R,L_{m},\mathcal{T})$ theory is still ambiguous. The orthogonal decomposition of the Riemann tensor results in the emergence of complexity factor as recently proposed by Herrera [1]. We initiate the analysis by contemplating the interior spacetime as a static spherical anisotropic composition under the presence of charge. The modified field equations are derived along with the establishment of association between the curvature and conformal tensors that have significant relevance in evaluating complexity of the system. Furthermore, the generalized expressions for two different masses are calculated, and their link with conformal tensor is also analyzed. Moreover, we develop a particular relation between predetermined quantities and evaluate the complexity in terms of a certain scalar $Y_{TF}$. Several interior solutions admitting vanishing complexity are also determined. Interestingly, compact objects having anisotropic matter configuration along with the energy density inhomogeneity possess maximum complexity. It is concluded that the spherical distribution of matter might not manifest complexity or admitting minimal value of this factor in the framework of $f(R,L_{m},\mathcal{T})$ theory due to the appearance of dark source terms.

gr-qc↗

arXiv2024

Optical Properties and Thermal Geometries of Hot NUT-Kerr-Newman-Kasuya-AdS Spacetime

This paper is devoted to studying the optical and thermal geometrical properties of Hot, NUT-KerrNewman-Kasuya-AdS black hole (BH). This BH is characterized by the NUT charge and a parameter Q that comprises the electric and magnetic charge. We compute the image of the BH shadow in two types: 1) at infinity, 2) at specific limit by analytical approach. We also investigate the effect of Nut, spin, inclination angle, and cosmological constant on the shape of shadow. We analyze that for type 1, the shadow in increasing for higher values of NUT charge, the cosmological constant, rotation parameters, and inclination angle, while for type 2, by increasing these parameters, the circular symmetry of the image of the BH shadow variate. Moreover, we discuss well-known thermal geometries such as Weinhold, Ruppeiner, HPEM, and Quevedo case I & II spacetime. It is found that Ruppeiner , HPEM and Quevedo (II) formulations provide physical information about the microscopic structure as compared to Weinhold and Quevedo (I) geometries of Hot NUT-Kerr-Newman-Kasuya-AdS BH. Our findings provides distinctive characteristics in the shadow and thermal geometries of this BH as compare to other BH types.

gr-qc↗