Gravastar Configurations in Rastall Gravity with Quintessence Effect under the Krori-Barua Metric

Abstract

This work presents the construction of a charged gravastar model within the framework of Rastall gravity, incorporating a quintessence dark energy field and employing the Krori-Barua metric ansatz for the interior spacetime. The gravastar configuration is modeled as a three-layered structure: a singularity-free de Sitter-like core (p = −ρ), an intermediate stiff-fluid shell (p = ρ), and an exterior region described by diverse charged vacuum geometries, including Schwarzschild, Reissner-Nordström-de Sitter, Reissner-Nordström-Kiselev, and Ayon-Beato-García spacetimes. By applying the Israel-Darmois-Lanczos junction conditions, we determine that the shell possesses a negative surface energy density and positive surface pressure, confirming the presence of exotic matter necessary to prevent gravitational collapse and event horizon formation. Detailed investigations into the shell’s physical properties, including proper length, energy content, and entropy, reveal that the charge significantly modifies the system’s energy distribution. Furthermore, we establish the thermodynamic stability of the model through the entropy maximization principle. Our analysis demonstrates that the shell entropy increases monotonically with thickness and that the second variation of the entropy functional remains strictly negative under radial perturbations. This confirms that the gravastar resides in a state of stable equilibrium in accordance with the second law of thermodynamics. Ultimately, these findings suggest that gravastars in modified Rastall gravity serve as robust, horizon-free, and singularity-free alternatives to classical black holes. Finally, we derive an analytical mass-radius relationship for the configuration, demonstrating that the compactness parameter consistently satisfies the condition $\mathcal {C}_{comp} < 1$. This ensures the absence of an event horizon and establishes the gravastar as a physically viable, horizon-free alternative to singular black holes.