Jena 2013 – scientific programme

Parts | Days | Selection | Search | Updates | Downloads | Help

GR: Fachverband Gravitation und Relativitätstheorie

GR 14: Kosmologie II

GR 14.3: Talk

Thursday, February 28, 2013, 17:00–17:15, HS 6

The trajectories of photons in an averaged space time — •Samae Bagheri — Uni Bielefeld D6-136, Universitätsstr. 25, 33615 Bielefeld

The present state of the Universe is neither homogeneous nor isotropic on scales smaller than 100 Mps. By taking the principal assumption of spatial homogeneity and isotropy on the largest scales, the averaging of local inhomogeneities can lead to dynamical effects on the evolution of the Universe. There are a number of averaging procedures that have been introduced in order to study this subject. We will describe two of the main schemes that can deal with inhomogeneities. One is Buchert's averaging which only scalar quantities are averaged and second is Zalaletdinov's averaging. The later allows tensor quantities to be averaged, as well as scalars. As the next step, we will discuss about the motion of photons in an averaged geometry within the context of the geodesic equation. All conclusions about cosmological data are based on the trajectories of photons. We consider the case of a null geodesic in the FLRW background space time. After averaging we obtain a smoothed out geometry with averaged metric. By doing so, we aim to pose the question of what trajectories photons follow in the averaged geometry.