Narrow Results

This paper studies the gravitational collapse of charged anisotropic spherical stellar objects in $f({𝒢})$ gravity. For this purpose, we derive dynamical equations by considering Misner–Sharp mechanism and explore physical impact of charge, anisotropy and effective pressure on the rate of collapse. We establish the relationship between matter variables, Weyl tensor and the Gauss–Bonnet (GB) terms. For constant value of $f({𝒢})$, it turns out that conformal flatness condition is no longer valid due to the effect of anisotropic factor in the present scenario. To obtain conformally flat metric, we impose the condition of isotropic matter distribution which provides energy density homogeneity and conformal flatness of the metric. We conclude that GB terms lead to decrease in the collapse rate due to their anti-gravitational effects.

The aim of this paper is to study the gravitational collapse of charged cylindrical star in $f({𝒢})$ gravity. For this purpose, we derive dynamical equations by applying Misner–Sharp formalism and examine the effects of effective pressure and charge on the collapse rate. We also construct a relationship between matter variables, Gauss–Bonnet (GB) terms, and the Weyl tensor. For the constant value of $f({𝒢})$, it is found that spacetime is conformally flat if and only if the energy density is homogeneous. We conclude that the rate of collapse slows down in $f({𝒢})$ gravity due to anti-gravitational effects.

In the context of modified $f({𝒢})=\alpha {{𝒢}}^n+\beta {𝒢}ln({𝒢})$ gravity model, the current study highlights the effect of electric charge for static spherically symmetric stellar models in presence of anisotropic matter distribution. For this purpose, we specifically consider the metric potentials of Tolman–Kuchowicz space–time, which are singularity free and satisfy the stability criteria. The possible existence of charge and a strong electric field, inside the stars is due to the higher values of energy density of matter, pressure distribution and gravitational fields. For the solution of Einstein–Maxwell field equations, the simplified phenomenological MIT bag equation of state, i.e. $p_r=\frac{1}{3}(\rho -4Bg)$ and a specific form of electrical charge distribution $q(r)=Q{\left(\frac{r}{R}\right)}^3=\mathrm{\Psi }{r}^3$ are to be considered. Further, to derive the values of unknown parameters of the stellar objects, we match interior Tolman–Kuchowicz space–time to exterior Reissner–Nordström metric, at the surface of stellar system. In addition to this, for the physical validity and stability of our suggested model, we conduct several physical tests such as effective energy density, effective pressures, energy conditions, stability against equilibrium of the forces, mass-radius relation, surface redshift, Herrera’s cracking concept and electric charge for well-known compact stellar objects viz., SAX J 1808.4-3658 and PSR 1937+21. It is observed that all these tests follow the physically accepted pattern and the influence of charge leads to more stable and viable stellar structures of compact objects in $f({𝒢})$ gravity.

This paper investigates inflationary dynamics for isotropic and homogeneous universe model in the background of $f({𝒢})$ gravity. We construct Hubble-flow functions, slow-roll parameters, amplitude of scalar power spectrum, spectral index and tensor–scalar ratio for a particular form of equation of state which describes quasi-de Sitter expansion. The dynamics of inflationary epoch is analyzed for scalar field as well as fluid cosmology with viable power-law $f({𝒢})$ model. We obtain different potential functions that correspond to chaotic inflation and Starobinsky type models. The graphical behavior of these parameters shows compatible results with observational Planck 2015 data in this gravity.

The aim of this paper is to study the dynamical instability of expansion-free spherically symmetric anisotropic fluid in the framework of $f({𝒢})$ gravity. We apply perturbation scheme of the first-order to the metric functions as well as matter variables and construct modified field equations for both static and perturbed configurations using power-law $f({𝒢})$ model. To discuss the instability dynamics, we use the contracted Bianchi identities to formulate the dynamical equations in both Newtonian and post-Newtonian regimes. It is found that the range of instability is independent of adiabatic index for expansion-free fluid but depends on anisotropic pressures, energy density and Gauss–Bonnet (GB) terms.

In this paper, we explore decoupled anisotropic interior solutions for static sphere using extended gravitational decoupling technique in $f({𝒢})$ gravity. We choose Tolman-IV solution as the isotropic interior source describing compact spherical geometry and extend its domains to determine two anisotropic models using some physical constraints. We test physical acceptability of both models for the compact star PSRJ1416-2230 through physical parameters, energy bounds and causality condition. It is observed that both models are physically viable as well as stable. It is also found that the first star model becomes more dense at its core as compared to the second for a small increase in the coupling constant $\xi$.

The current study examines the geometry of static wormholes with anisotropic matter distribution in the context of modified $f({𝒢})$ gravity. We consider the well-known Noether and conformal symmetries, which help in investigating wormholes in $f({𝒢})$ gravity. For this purpose, we develop symmetry generators associated with conserved quantities by taking into consideration the $f({𝒢})$ gravity model. Moreover, we use the conservation relationship gained from the classical Noether method and conformal Killing symmetries to develop the metric potential. These symmetries provide a strong mathematical background to investigate wormhole solutions by incorporating some suitable initial conditions. The obtained conserved quantity performs a significant role in defining the essential physical characteristics of the shape-function and energy conditions. Further, we also describe the stability of obtained wormholes solutions by employing the equilibrium condition in modified $f({𝒢})$ gravity. It is observed from graphical representation of obtained wormhole solutions that Noether and conformal Killing symmetries provide the results with physically accepted patterns.