Logarithmic gravity model.

In this paper, the modified F (R) gravity theory with the function F (R) = − (1 / β) ln (1 − β R) is studied. The action at small coupling β becomes Einstein–Hilbert action. The bound on the parameter β from local tests is β ≤ 2 × 1 0 − 6 cm2. We find the constant curvature solutions and it was shown that the de Sitter space is unstable but a solution with zero Ricci scalar is stable. The potential and the mass of the scalar field (scalaron) are obtained in Einstein's frame. The slow-roll cosmological parameters are studied and e-folds number is evaluated. The critical points of autonomous equations are analyzed. The function m (r) that describes the deviation from the Λ CDM model is calculated. [ABSTRACT FROM AUTHOR]