arXiv subjects

Mahmood Roshan

Publications and source records attributed to Mahmood Roshan.

56 records · Page 4Linked to original sources

arXiv2009

Cosmological solutions of time varying speed of light theories

We consider scalar-tensor theory for describing varying speed of light in a spatially flat FRW space-time. We find some exact solutions in the metric and Palatini formalisms. Also we examine the dynamics of this theory by dynamical system method assuming a $Λ$CDM background and we find some exact solutions by considering the character of critical points of the theory in both formalisms. We show that for any attractor the form of non-minimal coupling coefficient is quadratic in terms of the scalar field $Ψ$. Also we show that only attractors of the de Sitter era satisfy the horizon criteria.

gr-qc↗

arXiv2008

Palatini f(R) gravity and Noether symmetry

We study Palatini f(R) cosmology using Noether symmetry approach for the matter dominated universe. In order to construct a point-like Lagrangian in the flat FRW space time, we use the dynamical equivalence between f(R) gravity and scalar-tensor theories. The existence of Noether symmetry of the cosmological f(R) Lagrangian helps us to find out the form of f(R) and the exact solutions for cosmic scale factor. We show that this symmetry always exist for f(R)~R^n and the Noether constant is a function of the Newton's gravitational constant and the current matter content of the universe.

gr-qc↗