Emergence of dynamical dark energy from polynomial $f(R)$ theory in Palatini formalism

Understand

We consider FRW cosmology in $f(R)= R+ \gamma R^2+\delta R^3$ modified framework.

• The Palatini approach reduces its dynamics to the simple generalization of Friedmann equation.
• Thus we study the dynamics in two-dimensional phase space with some details.
• After reformulation of the model in the Einstein frame, it reduces to the FRW cosmological model with a homogeneous scalar field and vanishing kinetic energy term.