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The main objective of this manuscript is to investigate the bouncing cosmology in the background of f (Q) gravity, where Q defines the non-metricity. For this purpose, we use the reconstruction approach and consider a flat Friedmann–Robertson–Walker spacetime with perfect matter configuration. We examine how the first contracting phase gives the expansion by using a temporal derivative of the scale factor, i.e., a ̇ < 0 , a ̇ = 0 and a ̇ > 0 give contraction, bounce point and expansion phases, respectively. Further, we use the order reduction method to solve the modified field equations as these are very difficult due to the presence of additional non-linear expressions. It is analyzed that the original singularity of the universe diminishes for the required bounce conditions. We conclude that the acceleration occurs near the bouncing point and the considered f (Q) models are consistent with the current cosmic accelerated expansion. • Investigate the bouncing cosmology in the background of f(Q) gravity. • We use the reconstruction approach for a flat FRW spacetime with perfect matter configuration. • Examine how the first contracting phase gives the expansion through the scale factor. • The original singularity of the universe diminishes for the required bounce conditions. • The considered models of this gravity are consistent with the current cosmic accelerated expansion. [ABSTRACT FROM AUTHOR]

This paper uses the gravitational decoupling through the minimal geometric deformation approach and extends a known isotropic solution for a self-gravitating interior to two types of anisotropic spherical solutions in Rastall gravity in the presence of electromagnetic field. By deforming only the radial metric component, the field equations are decoupled into two sets, the first of which corresponds to an isotropic distribution of matter while the second set contains the anisotropic source. We obtain a solution of the first set by employing the charged isotropic Finch-Skea ansatz, whereas a solution for the second set is obtained by adopting two mimic constraints on the pressure and density. The matching conditions at the stellar surface are explored with the exterior geometry given by the deformed Reissner–Nordström spacetime. For the two fixed values of the Rastall and charge parameters, we investigate physical features of both solutions through graphical analysis of the energy conditions, equation of state parameters, surface redshift and compactness function. The stability of both solutions is also studied through the Herrera cracking approach and causality condition. We deduce that while both solutions are physically viable, only the solution corresponding to the pressure-like constraint is stable. • Gravitational decoupling approach is used to find charged exact solutions in Rastall gravity. • We obtain a solution by employing charged isotropic Finch-Skea ansatz. • Investigate physical viability of both solutions through graphical analysis of the physical quantities. • Stability of both solutions is also studied through the Herrera cracking approach and causality condition. • We deduce that both solutions are physically viable but only the first solution is stable. [ABSTRACT FROM AUTHOR]

This paper is devoted to the study of curvature properties of Hayward black hole (briefly, HBH) spacetime, which is a solution of Einstein field equations (briefly, EFE) having non-vanishing cosmological constant. We have proved that the HBH spacetime is an Einstein manifold of level 2, 2-quasi Einstein, generalized quasi-Einstein and Roter type manifold. Also, it is shown that the nature of the HBH spacetime is pseudosymmetric and it obeys several types of pseudosymmetries, such as, pseudosymmetry due to concircular, conformal and conharmonic curvature (i.e., F ⋅ F = L Q (g , F) for F = W , C , K with a smooth scalar function L), and it also possesses the relation R ⋅ R − L Q (g , C) = Q (S , R). It is engrossing to mention that the nature of energy momentum tensor of the HBH spacetime is pseudosymmetric. On the basis of curvature related properties, we have made a comparison among Reissner–Nordström spacetime, interior black hole spacetime and HBH spacetime. It is noteworthy to mention that the gravitational force of the point-like global monopole spacetime is much stronger than that of HBH spacetime. Also, it is shown that the HBH spacetime admits an almost η -Ricci soliton as well as an almost η -Ricci-Yamabe soliton. Finally, an elegant comparative study is delineated between the HBH spacetime and the point-like global monopole spacetime with respect to different kinds of symmetry, such as, motion, curvature collineation, curvature inheritance etc. • This paper aims to the study of curvature properties of Hayward black hole spacetime. • We have proved that the spacetime is an Ein(2), 2-quasi Einstein and Roter type. • Also shown that the nature of the spacetime obeys several types of pseudosymmetries. • We have compared Reissner–Nordström, interior black hole and HBH spacetime. • Also, the HBH spacetime admits an almost η -Ricci and almost η -Ricci-Yamabe solitons. [ABSTRACT FROM AUTHOR]

The Vaidya and Tikekar (1982) ansatz has so far provided numerous stellar solutions which are useful for the description of compact stars like neutron stars and quark stars. We re-examine the impacts of the spacetime curvature parameter of the Vaidya–Tikekar ansatz on the physical properties of the relativistic anisotropic star. For a spherically symmetric, static and anisotropic stellar configuration, in the Vaidya–Tikekar background spacetime, we develop new exact solutions by assuming a polytropic type equation of state p r = k ρ 1 + 1 n − β. Recent data from observed pulsars are taken as input parameters to validate the developed model. We examine the impact of the spheroidal curvature parameter of the VT spacetime on the stellar behaviour and mass–radius (M–R) relationship. It is observed that with the increase in the departure from spherical geometry, values of physical quantities, such as density and pressure, increase. • We have found a stable model of compact stars and fulfils all the regularity conditions and physical requirements. • An interesting feature of the model is that it provides a free parameter K, which makes it suitable for the description of a wide range of compact stars. [ABSTRACT FROM AUTHOR]

In the standard cosmological model the dark energy (DE) and nonrelativistic (NR) matter densities are observationally determined to be comparable at the present time, in spite of their greatly different evolution histories. This 'cosmic coincidence' enigma – also referred to as the 'why now? problem' – relies, by its very definition, on the implicit prior expectation for our 'typicality' in the cosmic (expanding) spacetime volume. Otherwise, this conundrum does not exist in the first place. It is shown here that this apparent coincidence could be explained as a non-anthropic observational selection effect: for us to be typical observers in the comoving (static) spacetime volume, the cosmic energy budget must contain a non-vanishing DE component. In addition, it is shown that irrespective of the cosmological initial conditions and assuming no 'new physics', the Universe is most likely to be observed at a time when the conformal Hubble radius, H − 1 , attains a maximum. The latter takes place at the epoch when ρ D E and ρ m , the energy densities of DE and NR matter, respectively, are comparable. Specifically, our presumed 'typicality' along the conformal timeline, coupled to a few other plausible assumptions, implies that R ≡ ρ D E / ρ m is 'sampled' from a Beta Prime probability distribution function. A priori 68% (95%) confidence range for the ratio is 0. 20 < R < 3. 46 (0. 033 < R < 17. 20), with an expectation value of R ̄ = 3. 5. These are in agreement with the observationally inferred value, R o b s = 2. 23. • Cosmic Coincidence problem admits non-anthropic solutions. • Typical observers could be uniformly distributed in comoving spacetime. • Meaningful uniform distribution requires the existence of dark energy. • The distribution is peaked in redshift space thanks to the Friedmann equation. • Peak corresponds to crossover between decelerated and accelerated expansion. [ABSTRACT FROM AUTHOR]

Gravitational weak lensing around a hairy black hole has been deeply studied in the presence of a plasma medium. The obtained results have shown that the effect of parameters a and l 0 on the deflection angle of light rays around the black hole in hairy spacetime is perceptible. With an increase of parameter a the deflection angle of photon orbits decreases, and the effect of plasma on the deflection angle is the opposite. Here, we discussed different types of plasma distributions: uniform ω e = c o n s t , Singular Isothermal Sphere medium, 1 / r and Non-Singular Isothermal gas sphere plasma. Additionally, The total magnification of the image source due to gravitational lensing has been also studied taking into account the effect of deviation parameter a and parameter l 0 related to hairy spacetime in the presence of plasma around the black hole. • Gravitational weak lensing around a hairy black hole has been deeply studied in the presence of a plasma medium. • The obtained results have shown that the effect of parameters a and I 0 on the deflection angle of light rays around the black hole in hairy spacetime is perceptible. • Here, we discussed different types of plasma distributions: uniform ω e = const , Singular Isothermal Sphere medium, 1 /r, and Non-Singular Isothermal gas sphere plasma. • The total magnification of the image source due to gravitational lensing has been also studied. [ABSTRACT FROM AUTHOR]