Scale factor dependent equation of state for curvature inspired dark energy, phantom barrier and late cosmic acceleration

Abstract

Here, it is found that dark energy and dark matter emerge from the gravitational sector, if non-linear term of scalar curvature is added to Einstein–Hilbert Lagrangian. An equation of state for dark energy, having the form p de = − ρ de + f ( a ) (with p de ( ρ de ) being the pressure (density) for dark energy, f ( a ) being a function of scale factor a ( t ) and t being the cosmic time) is explored. Interestingly, this equation of state leads to a phantom barrier w de = p de / ρ de = − 1 at a = a w . It is found that when a < a w , w de > − 1 and w de < − 1 for a > a w , showing a transition from non-phantom to phantom phase at a = a w < a 0 ( a 0 being the current scale factor of the universe).