Reconstruction and stability analysis of some cosmological bouncing solutions in F(ℛ,T) theory.

This paper investigates the possibility of reconstruction of the generic function in F (ℛ , T) gravitational theory by considering some well-known cosmological bouncing models, namely, exponential evaluation, oscillatory, power law and matter bounce model, where ℛ and T are Ricci scalar and trace of energy–momentum tensor, respectively. Due to the complexity of dynamical field equations, we propose some ansatz forms of function F (ℛ , T) in perspective models and examine which type of Lagrangian is capable of reproducing bouncing solution via analytical expression. It is seen that for some cases of exponential, oscillatory and matter bounce models, it is possible to get analytical solution while in other cases, it is not possible to achieve exact (general) solutions so only complementary solutions can be discussed. However, for power-law model, all forms of generic function can be reconstructed analytically. Next we analyze the energy conditions and stability of these reconstructed cosmological bouncing models which have analytical forms. It is found that these models are stable for linear forms of Lagrangian only but the reconstructed solutions for power law are unstable for some nonlinear forms of Lagrangian. Further, we determine the observable quantities like spectral index ( n s ) and tensor-to-scalar ratio (r) for the simplest reconstructed form of f (R , T) function. As a result, we directly confront the reconstructed linear form of Lagrangian in F (ℛ , T) model with 2018 Planck observations. Furthermore, we analyze that F (ℛ , T) gravity with dark energy epoch is consistent with Sne-Ia+BAO+H(z)+CMB data and show that bounce can unify with dark energy epochs in F (ℛ , T) gravity. [ABSTRACT FROM AUTHOR]