Viscous modified Chaplygin gas with spherical top-hat collapse in modified theories of gravity

Abstract The work explores the dynamics of a spherically symmetric perturbation of viscous modified Chaplygin gas (VMCG) in different gravity theories within the spherical top hat collapse framework (SC-TH). The study investigates the behaviour of perturbed quantities such as the δ , θ , w , w c , c s 2 , c e 2 , and h using numerical and graphical analysis. Our findings reveal that VMCG generates quintessential dark energy without crossing over to the phantom barrier in most of the gravity models considered here. Further, in all the gravity models considered here, VMCG remained classically stable. This research offers new insights into the evolution of VMCG in different gravitational contexts. In this paper, we have examined the collapse of viscous modified Chaplygin gas in the context of (i) Einstein’s gravity, (ii) Loop quantum cosmology, (iii) generalised Rastall gravity, and (iv) the fractal universe. We have also addressed their comparative analysis.