arXiv subjects

M. Zeeshan Gul

Publications and source records attributed to M. Zeeshan Gul.

At least 19 recordsLinked to original sources

arXiv2026

Particle Dynamics and Thermodynamics of a Charged-Like Hairy Black Hole in Extended Gravitational Decoupling

This work focuses on the analysis of particle dynamics and the thermodynamic properties associated with a particular branch of hairy black hole solutions. These solutions are obtained by using extended geometric deformation gravitational decoupling on the seed solution of the Schwarzschild solution. This resulting geometry satisfies the dominant energy condition and the condition $Q^{2}=2χ\ell M$. We analyze the motion of massive particles and photons in this geometry and the thermodynamics of this solution. In particular, for massless particles, we study the effective potential and determine the radii of the photon sphere and the shadow of the black hole. For massive particles, we calculate the specific energy and angular momentum of circular orbits, the ISCO, the radiative efficiency of an accretion disk, and representative particle trajectories. Finally, we investigate the thermodynamic properties of this hairy black hole geometry, including the Hawking temperature, the Bekenstein-Hawking entropy, and the heat capacity in the fixed-$(Q,\ell)$ ensemble.

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arXiv2026

Reeb-Wolf Improved Landauer Principle for Hairy Black Holes via Gravitational Decoupling

We investigated the thermodynamic and quantum-information cost of irreversible information erasure at the event horizon of hairy black holes generated through extended geometric deformation. Starting from the Schwarzschild black hole seed solution, we considered two families of hairy geometries satisfying the strong and dominant energy conditions. Lan-dauer's principle was used to relate the minimum energy required to erase one bit of information to the Hawking temperature of deformed horizon. We derived corresponding horizon radii, Hawking temperatures, Bekenstein-Hawking entropies and normalised Landauer costs as functions of decoupling parameter, the hair length scale and the effective charge associated with the additional gravitational sector. For the parameter ranges analyzed, our results show that gravitational hair tends to reduce the Hawking temperature and the minimum Landauer erasure cost while simultaneously increasing the horizon area and the Bekenstein-Hawking entropy. The Reeb-Wolf finite-size correction provides an additional positive contribution to the erasure cost but remains subdominant due to the large effective dimension of the horizon reservoir. We further separated the Reeb-Wolf correction into mutual-information and relative-entropy contributions, showing that the former is governed by the area-spacing parameter, whereas the latter is controlled by the actual energy gap between neighboring horizon levels. Furthermore, the Landauer spectrum obtained by quantizing the area decreases as the quantum number associated with the horizon increases, although this variation does not occur in the same way in the SEC and DEC branches. Overall, the presence of gravitational hair alters the thermodynamic properties of the horizon and, consequently, the Landauer cost associated with information erasure, both in the continuous regime and after quantizing the area.

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arXiv2026

Bulk Viscosity and Thermodynamic Approaches to Singularity Resolution in Non-Metric Gravity

This manuscript investigates the impact of bulk viscosity on the viability of cosmic bounce solutions in the context of $f(\mathcal{Q})$ theory, where $\mathcal{Q}$ is a non-metricity scalar. To complete this objective, we study the behavior of an isotropic homogeneous universe filled with a perfect fluid and consider a innovative parametrization of bulk viscosity coefficient with an arbitrary constant $ζ_0$ as $ζ=ζ_{0}H$. We consider the particular functional form of this modified theory to explore how this gravitational framework influences the cosmic evolution and explore a range of cosmological parameters to assess the existence and physical viability of bounce solutions. We also investigate the evolution of entropy through the second law of thermodynamics. The positive trend of energy density, negative pressure profile and violation of energy conditions support the existence of viable cosmological bounce scenario and highlights the significance of bulk viscosity in this framework. These results demonstrate that $f(\mathcal{Q})$ gravity provides a compelling alternative to standard cosmic models and provides deep insights into the nature of gravitational interaction and the early cosmos.

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arXiv2026

Beyond Classical Instability Limits of Anisotropic Self-gravitating Fluid Configurations in Hu-Sawicki Inspired f(R) Gravity

In this draft, we investigate the dynamical instability of a restricted class of non-static, axially symmetric, self-gravitating fluid configurations within a Hu-Sawicki inspired f(R) gravity model. The matter source is described by an anisotropic energy-momentum tensor containing three principal stresses and an off-diagonal stress component. For the adopted vorticity free geometry, conservation equations are formulated, and a linear perturbation scheme is applied to separate the equilibrium and time-dependent sectors. This procedure yields a collapse equation that governs the evolution of the perturbed compact configuration. The associated instability conditions are then derived in terms of the adiabatic index Γ under the Newtonian and post-Newtonian approximations, whereas the resulting bounds show that the onset of instability depends not only on the stiffness of the fluid, but also on the background energy density, directional pressure anisotropies, metric perturbations, and higher-curvature contributions generated by the Hu-Sawicki model. The general relativistic limit is recovered by suppressing the modified gravity parameters, while the isotropic limit reproduces the classical Chandrasekhar threshold. These results demonstrate that curvature corrections and anisotropic stresses can appreciably modify the conventional instability conditions of axially symmetric compact systems.

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arXiv2026

Feasible Stellar Interiors Beyond Einstein Gravity: Insights from Non-Metricity-Matter Coupled Gravitational Theory

This manuscript examines viability and stability of anisotropic compact objects in the framework of $f(Q,L_m)$ gravity ($Q$ is the non-metricity and $L_m$ is the matter Lagrangian). We assume a particular functional form of this theory to get explicit expressions for the field equations which govern the behavior of matter and geometry in this context. The configuration of static spherically symmetric structures is evaluated using the two innovative non-singular solutions. We use smooth matching conditions to evaluate the values of unknown constants in the metric coefficients. The viability of considered compact stars is assessed using a graphic analysis of various important physical characteristics. We also investigate stability of the considered stellar objects through sound speed method. It is found that these stellar objects are viable and stable, as all the required conditions are satisfied.

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arXiv2026

Comparative Analysis of Holographic Dark Energy Models in $f(R,T^2)$ Gravity

This study investigates the Renyi Holographic dark energy, Sharma-Mittal Holographic dark energy and Generalized Holographic dark energy models in the framework of $f(R,T^2)$ gravity, where $R$ denotes the Ricci scalar and $T^2$ represents the self-contraction of the stress-energy tensor. For this purpose we employed two horizons as infrared cut-offs, such as Hubble horizon and Ricci horizon. The analysis is conducted for a non-interacting scenario in a spatially flat Friedmann-Robertson-Walker universe. By considering a specific form of this modified gravity, we reconstruct the corresponding gravitational models based on these selected dark energy formulations. Additionally, a stability analysis is performed for all cases and the evolution of the equation of state parameter is examined. Our finding indicates that the reconstructed $f(R,T^2)$ models effectively describe both the phantom and quintessence phases of cosmic evolution, aligning with the observed accelerated expansion of the universe. This study highlights the deep interconnections between holographic dark energy models and modified gravity theories, offering valuable insights into the large scale dynamics of the cosmos.

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arXiv2025

The Dynamics of Cosmic Evolution: Insights from Bouncing Cosmology

The primary aim of this work is to explore feasible bouncing cosmological solutions in the framework of $f(\mathcal{Q}, \mathcal{C})$ gravity, where $\mathcal{Q}$ denotes non-metricity and $\mathcal{C}$ indicates the boundary term. To achieve this, we analyze the dynamics of a Bianchi type-I spacetime with perfect fluid distribution. We consider various functional forms of $f(\mathcal{Q,C})$ theory to assess how this modified gravity framework influences cosmic evolution. Additionally, we examine the dynamics of different cosmological parameters to explore non-singular bounce solutions. We also use linear perturbation to study the stability analysis. Our findings reveal the breach of the null energy conditions, which is required for the existence of viable bounce solutions. The equation of state parameter demonstrates either a quintessence phase or a phantom regime of the universe, demonstrating that the cosmos is undergoing accelerating expansion. This gravitational framework presents a promising alternative to the standard cosmological model, presenting an innovative viewpoint on gravitational interactions and the dynamics of the early universe.

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arXiv2025

Study of Complexity Factor and Stability of Dynamical Systems in $f(G)$ Gravity

In this paper, we evaluate the complexity of the non-static cylindrical geometry with anisotropic matter configuration in the framework of modified Gauss-Bonnet theory. In this perspective, we calculate modified field equations, the C energy formula, and the mass function that helps to understand the astrophysical structures in this modified gravity. Furthermore, we use the Weyl tensor and obtain different structure scalars by orthogonally splitting the Riemann tensor. One of these scalars, $YTF$ is referred to as the complexity factor. This parameter measures the system's complexity due to non-uniform energy density and non-isotropic pressure. We select the identical complexity factor for the structure as used in the non-static scenario while considering the analogous criterion for the most elementary pattern of development. This technique involves formulating structural scalars that illustrate the fundamental features of the system. A fluid distribution that satisfies the vanishing complexity requirement and evolves homologously is characterized as isotropic, geodesic, homogeneous, and shear-free. In the dissipative scenario, the fluid remains geodesic while exhibiting shear, resulting in an extensive array of solutions.

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arXiv2025

Impact of Non-metricity and Matter Source on the Geometry of Anisotropic Spheres

This paper delves into the impact of extended symmetric teleparallel theory on anisotropic compact stellar structures. The explicit field equations were formulated by considering a minimum model of this extended gravity. Basically, the Darmois junction conditions are used to determine the unknown constants of metric coefficients. We explore some significant properties of the compact stars under consideration to check their viable existence in this modified framework. The Tolman-Oppenheimer-Volkoff equation assess the equilibrium state of the compact stars. Moreover, the stability analysis is defined by using methods based on sound speed (related to how disturbances propagate in the star) and adiabatic index (related to the thermodynamic behavior of the star). We find that the proposed compact stars in the $f(\mathbb{Q}, \mathbb{T})$ gravity are physically viable and stable.

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arXiv2025

Comprehensive Study of Generalized Ghost Dark Energy in $f(\textsl{Q}, \textsl{L}_{m})$ Gravity: New Insights into Cosmic Dynamics

This paper explores the generalized ghost dark energy model in the framework of $f(\textsl{Q}, \textsl{L}_{m})$ gravity, where $\textsl{Q}$ represents the non-metricity scalar and $\textsl{L}_{m}$ denotes the matter-Lagrangian density. We take the homogeneous and isotropic universe with an ideal matter distribution and examine a scenario with interacting dark energy and dark matter. We then reconstruct $f(\textsl{Q}, \textsl{L}_{m})$ model to examine the effects of this extended gravitational framework on the cosmic evolution. The behavior of numerous cosmic parameters are explored corresponding to distinct parametric values. The stability is evaluated by the squared sound speed method. The statefinder $(r,s)$ and standard diagnostic pairs $(ω_D-ω'_{D})$ are used to study the various cosmic eras. Our results align with recent observational evidence, indicating that the $f(\textsl{Q}, \textsl{L}_{m})$ model effectively characterizes dark energy and cosmic evolution.

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arXiv2024

Exploring the viability of charged Spheres admitting non-metricity and matter source

This research paper investigates the impact of non-metricity and matter source on the geometry of charged spheres in the presence of anisotropic matter configuration. We use a specific model of extended symmetric teleparallel theory to minimize the complexity of the field equations. Moreover, the feasible non-singular solutions are used to examine the interior composition of the charged spheres. The Darmois junction conditions are used to determine the unknown constants in the metric coefficients. We explore some significant properties in the interior of compact stars under consideration to check their viable existence in this modified framework. The equilibrium state of the charged spheres is discussed using the Tolman-Oppenheimer-Volkoff equation and stability is analyzed by sound speed and Herrera cracking approach. We find that the charged spheres in this theoretical framework are physically viable and stable.

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arXiv2024

Viable Wormhole Structures and Energy Conditions in f(Q,T) Theory

This paper explores static wormhole solutions in f(Q,T) theory, where Q is the non-metricity and T is the trace of energy-momentum tensor. We derive the field equations that describe gravitational phenomena in the existence of non-metricity and matter source terms. We examine different models of this theory to determine the explicit expressions of matter contents, which are useful for analyzing the wormhole structures. We investigate the existence of feasible traversable wormhole solutions for constant and variable redshift functions. To determine whether physically viable wormhole geometry exists, we examine the graphical interpretation of energy constraints for different values of model parameters. It is found that realistic traversable and stable wormhole solutions exist only for the first model of this gravity.

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arXiv2024

Impact of $f(\mathcal{Q})$ Theory on the Stability of Compact Spherical Solutions

This research paper examines the feasibility and stability of compact stars in the context of $f(\mathcal{Q})$ theory, where $\mathcal{Q}$ represents the non-metricity scalar. To achieve this objective, a static spherical line element is assumed in the interior region and the Schwarzschild spacetime is used in the exterior region of the star. The unknown constants are determined by using the Darmois junction conditions. We consider a specific model of this theory to investigate the viability of compact stars through various physical quantities such as matter contents, energy bounds, anisotropy and state parameters. The stability states for the stellar objects under consideration are determined by the speed of sound and adiabatic index, respectively. The resulting data indicate that the compact stars in this modified framework are physically viable and stable.

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arXiv2024

Study of Cosmic Evolution admitting Thermodynamic Analysis

This article examines the cosmic evolution in the framework of symmetric teleparallel theory, characterized by the function of non-metricity scalar $(\mathcal{Q})$. We use the e-folding number and reconstruction method with a suitable parametrization of the scale factor to obtain the functional form of symmetric teleparallel theory. Using this reconstructed model, we examine the behavior of different cosmographic parameters to demonstrate the bouncing scenarios of the cosmos by considering the contraction and expansion phases of cosmos before and after the bouncing point, respectively. It is found that the null energy condition is violated which shows that the singularity issue can be resolved in this extended theoretical framework. Moreover, we observe that the acceleration occurs near the bouncing point and the reconstructed model aligns with the current cosmic expansion. Finally, we check the validity of second law of thermodynamics in the bouncing framework of our model.

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arXiv2024

Stability Analysis of Static Spherical Spacetime in Extended Symmetric Teleparallel Gravity

Our manuscript aims to analysis the viability and stability of anisotropic stellar objects in the modified symmetric teleparallel gravity. A particular model of this extended theory is considered to formulate explicit field equations which govern the interaction between matter and geometry. The configuration of static spherical symmetric structures is examined through the Finch-Skea solution. However, the values of unknown constants in the metric potentials are evaluated by the Darmois junction conditions. For the viability of proposed stellar objects, the physical parameters including density, pressure, anisotropy, mass, energy constraints, compactness function and redshift are analyzed. Furthermore, stability of the proposed stellar objects is investigated by causality condition, Herrera cracking approach and adiabatic index. Our findings indicate that the proposed stellar objects are viable as well as stable in the presence of correction terms.

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arXiv2024

Comprehensive Study of Bouncing Cosmological Models in $f(Q,T)$ Theory

The main objective of this article is to investigate the viability of bouncing cosmological scenarios using different forms of scale factors with perfect matter configuration in the framework of extended symmetric teleparallel theory. This modified proposal is defined by the function $f(Q,T)$, where $Q$ characterizes non-metricity and $T$ denotes the trace of energy-momentum tensor. We investigate the modified field equations of this theory using different parametric values of the Hubble parameter and non-metricity to derive viable solutions. These solutions are relevant in various cosmological bounce models such as symmetric-bounce, super-bounce, oscillatory-bounce, matter-bounce and exponential-bounce models. Furthermore, we examine the behavior of energy density and pressure to analyze the characteristics of dark energy. A comprehensive analysis is also conducted to explore the behavior of the equation of state parameter and deceleration parameter to examine the evolutionary eras of the cosmos. Our findings show that the $f(Q,T)$ gravity describes the cosmic expansion in the vicinity of the bouncing point during the early and late times of cosmic evolution.

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arXiv2024

Physical Analysis of Spherical Stellar Structures in $f(\mathrm{Q},\mathrm{T})$ Theory

This paper explores the viability and stability of compact stellar objects characterized by anisotropic matter in the framework of $f(\mathrm{Q},\mathrm{T})$ theory, where $\mathrm{Q}$ denotes non-metricity and $\mathrm{T}$ represents the trace of the energy-momentum tensor. We consider a specific model of this theory to obtain explicit expressions for the field equations governing the behavior of matter and geometry in this context. Furthermore, the Karmarkar condition is employed to assess the configuration of static spherically symmetric structures. The values of unknown constants in the metric potentials are determined through matching conditions of the interior and exterior spacetimes. Various physical quantities such as fluid parameters, energy constraints, equation of state parameters, mass, compactness and redshift are graphically analyzed to evaluate the viability of the considered compact stars. The Tolman-Oppenheimer-Volkoff equation is used to examine the equilibrium state of the stellar models. Moreover, the stability of the proposed compact stars is investigated through sound speed and adiabatic index methods. This study concludes that the proposed compact stars analyzed in this theoretical framework are viable and stable, as all the required conditions are satisfied.

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arXiv2024

Spherically Symmetric Wormhole Solutions admitting Karmarkar Condition

This paper investigated the viable traversable wormhole solutions through Karmarkar condition in the context of $f(\mathcal{G},T)$ theory. A static spherical spacetime with anisotropic matter configuration is used to study the wormhole geometry. Karmarkar condition is used to develop a viable shape function for a static wormhole structure. A wormhole geometry is constructed using the resulting shape function that satisfies all the required conditions and connects the asymptotically flat regions of the spacetime. To assess the viability of traversable wormhole geometries, the energy conditions are analyzed by various models of this theory. Further, their stable state is investigated through sound speed and adiabatic index. This investigation demonstrates the presence of viable traversable wormhole solutions in the modified theory.

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