Shear-free axial system and f(G) gravity

This paper investigates the influences of dark sources on the evolution of shear-free axially symmetric dissipative fluid in f(G) gravity. Matter contents (energy terms of the system), corresponding dynamical variables as well as scalar functions are derived in the presence of dark sources. The dark terms appear as one of the sources producing pressure anisotropy and heat dissipation. We then study non-geodesic and geodesic fluids with and without dissipation under shear-free condition. The non-geodesic (non-dissipative) fluid gives inhomogeneous expansion while the geodesic fluid makes the system either vorticity-free or expansion-free. The vorticity-free non-dissipative geodesic fluid reduces the axial system to FRW model in the presence of homogeneous distribution of dark sources while the expansion-free geodesic fluid does not exist even in the presence of dark sources.