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

Abstract

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. This potential determines the running cosmological constant term as a function of the Ricci scalar. As a result we obtain the emergent dark energy parametrization from the covariant theory. We study also singularities of the model and demonstrate that in the Einstein frame some undesirable singularities disappear.

8 pages, 15 figures

References in corpus (4)

• Palatini Approach to Modified Gravity: f(R) Theories and Beyond
• Limit to General Relativity in f(R) theories of gravity
• Why the cosmological constant is small and positive
• Physical non-equivalence of the Jordan and Einstein frames

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