Kinematics and Generalized Raychaudhuri equation in f(G) gravity in imperfect fluid case

TL;DR

This paper derives the generalized Raychaudhuri equation and extra force in F(G) gravity with an imperfect fluid, highlighting differences from F(R) gravity and their effects on kinematic evolution and particle acceleration.

Contribution

It introduces a new formulation of the Raychaudhuri equation and extra force in F(G) gravity considering imperfect fluids, extending previous perfect fluid models.

Findings

Extra force normal to four-velocity arises in F(G) gravity.

Generalized Raychaudhuri equation derived for imperfect fluids.

Differences from F(R) gravity in kinematic evolution and particle acceleration.

Abstract

The equation of motion is the important equation for obtain the extra force and Raychaudhuri equation. By considering an explicitly coupling between an arbitrary function of the scalar Gauss-Bonnet, G and the Lagrangian density of matter, it is shown that an extra force normal to their four-velocities arises. In this paper, we obtain the extra force and the generalized Raychaudhuri equation in F(G) modified theory of gravity in an imperfect fluid for the massive particle by divergence of energy momentum tensor so we earn extra force an Raychaudhuri equation in a compared with f(R) modified gravity for perfect fluid this conclusion giving the evolution of the kinematical quantities and describing the relative accelerations of nearby particles .