Observational constrained F(R,G)F(R, \mathcal{G}) gravity cosmological model and the dynamical system analysis

In this paper, we have analyzed the geometrical and dynamical parameters of $\mathcal{F}(R, \mathcal{G})=\alpha R^2 \mathcal{G}^\beta$ cosmological model, ($R$, $\mathcal{G}$ being the Ricci scalar and Gauss-Bonnet invariant respectively), constraining the parameters through the cosmological data sets. It is exhibited that the model admits a viable radiation era, and early deceleration followed by late-time acceleration in the matter-dominated era. From the phase-space, portrait stability criterion has been analysed, restricting the parameter $\beta$, different from $\beta=-1$. Additionally, we have explored the stability of the model from the behavior of critical points and obtained the present value of the density parameter for matter-dominated and dark energy components, which are identical to those obtained through cosmological data sets.Comment: 22 pages, 6 figure

Constraining f(T,T)f(T,\mathcal{T}) gravity from dynamical system analysis

The dynamical system analysis of the cosmological models in $f(T,\mathcal{T})$ gravity, where $T$ and $\mathcal{T}$ respectively represents the torsion scalar and trace of the energy-momentum tensor has been investigated. It demonstrates how first-order autonomous systems can be treated as cosmological equations and analyzed using standard dynamical system theory techniques. Two forms of the function $f(T,\mathcal{T})$ are considered (i) one with the product of trace and higher order torsion scalar and the other (ii) linear combination of linear trace and squared torsion. For each case, the critical points are derived and their stability as well the cosmological behaviours are shown. In both the models the stable critical points are obtained in the de-Sitter phase whereas in the matter and radiation dominated phase unstable critical points are obtained. At the stable critical points, the deceleration parameter shows the accelerating behaviour of the Universe whereas the equation of state parameter shows the $\Lambda CDM$ behaviour. Finally the obtained Hubble parameter of the models are checked for the cosmological data setsComment: 21 pages, 10 figures. Comments are welcom

Analyzing the geometrical and dynamical parameters of modified Teleparallel-Gauss-Bonnet model

To recreate the cosmological models, we employed the parametrization approach in modified teleparallel Gauss-Bonnet gravity. It has been interesting to apply the parametrization approach to investigate cosmological models. The real benefit of using this method is that the observational data may be incorporated to examine the cosmological models. Several cosmological parameters were examined, such as the Hubble parameter (H), the deceleration parameter (q), and the equation of state (EoS) parameter (w). The results obtained are consistent with recent cosmological findings in the conventional scenario. A transition scenario from a decelerating stage to an accelerating stage of cosmic evolution has been observed. The EoS parameter is also in the quintessence phase, which drives the accelerating expansion of the Universe. Also, we look at the violation of strong energy condition, which has become inevitable in the context of modified gravitational theory. Finally, we have performed the Om(z) diagnostic and also obtained the age of the Universe by using the data from the cosmological observations.Comment: 13 pages, 9 figure

Influence of three parameters on maximum mass and stability of strange star under linear f(Q)−f(Q)-action

This study simulates strange stars in $f(Q)$ gravity with an additional source under an electric field using gravitational decoupling and the complete Gravitational Decoupling (CGD) technique. By employing the Tolman ansatz and the MIT bag model equation of state (EOS), we explore bounded star configurations derived from the $\theta_0^0 = \rho$ and $\theta_1^1 = p_r$ sectors within the CGD formalism. Our models are subjected to physical viability tests, and we analyze the impact of anisotropy and the electric charge parameter $E_0$ as well as the coupling parameters $\alpha$ and $\beta_1$. Comparisons are made with observational constraints, including GW190814, neutron stars PSR J1614-2230, PSR J1903+6620, Cen X-3 and LMC X-4. Notably, we achieve the presence of a lower "\textit{mass gap}" component by adjusting parameters $\alpha$ and $\beta_1$. Our models exhibit well-behaved mass profiles, internal regularity, and stability, with the absence of gravitational collapse verified through the Buchdahl--Andr\'{e}asson's limit. In addition, we present a detailed physical analysis based on three parameters, $\alpha$ (decoupling strength), $\beta_1$ ($f(Q)$--coupling) and $Q$ (surface charge). This study provides insights into the behavior of compact objects in $f(Q)$ gravity and expands our understanding of strange star configurations within this framework.Comment: 18 pages, 18 figures, Accepted version Monthly Notices of Royal Astronomical Societ

Bouncing Cosmology in Modified Gravity with Higher-Order Gauss–Bonnet Curvature Term

In this paper, we studied the bouncing behavior of the cosmological models formulated in the background of the Hubble function in the F(R,G) theory of gravity, where R and G, respectively, denote the Ricci scalar and Gauss–Bonnet invariant. The actions of the bouncing cosmology are studied with a consideration of the different viable models that can resolve the difficulty of singularity in standard Big Bang cosmology. Both models show bouncing behavior and satisfy the bouncing cosmological properties. Models based on dynamical, deceleration, and energy conditions indicate the accelerating behavior at the late evolution time. The phantom at the bounce epoch is analogous to quintessence behavior. Finally, we formulate the perturbed evolution equations and investigate the stability of the two bouncing solutions

Dynamical stability analysis of accelerating

In this paper, we have emphasized the stability analysis of the accelerating cosmological models obtained in f(T) gravity theory. The behaviour of the models based on the evolution of the equation of state parameter shows phantom-like behaviour at the present epoch. The scalar perturbation technique is used to create the perturbed evolution equations, and the stability of the models has been demonstrated. Also, we have performed the dynamical system analysis for both the models. In the two specific f(T) gravity models, three critical points are obtained in each model. In each model, at least one critical point has been observed to be stable