Inflation in mimetic f(G) gravity

Abstract

Mimetic gravity is analysed in the framework of some extensions of General Relativity, where a function of the Gauss-Bonnet invariant in four dimensions is considered. By assuming the so-called mimetic condition, the conformal degree of freedom is isolated and a pressureless fluid naturally arises. Then, the complete set of field equations for mimetic Gauss-Bonnet gravity is established and some inflationary models are analysed, for which the corresponding gravitational action is reconstructed. The spectral index and tensor-to-scalar ratio are obtained and compared with observational bounds from Planck and BICEP2/Keck array data. The full agreement with above data is achieved for several versions of the mimetic Gauss-Bonnet gravity. Finally, some extensions of Gauss-Bonnet mimetic gravity are considered and the possibility of reproducing inflation is also explored.