MODIFIED AVERAGING PROCESSES IN COSMOLOGY AND THE STRUCTURED FRW MODEL

摘要

We study the volume averaging of inhomogeneous metrics within GR and discuss its shortcomings, such as gauge dependence, singular behavior as a result of caustics, and causality violations. To remedy these shortcomings, we suggest some modifications to this method. As a case study we focus on the inhomogeneous structured FRW model based on a flat LTB metric. The effect of averaging is then studied in terms of an effective backreaction fluid. It is shown that, contrary to the claims in the literature,the backreaction fluid behaves like a dark matter component, instead of dark energy, having a density of the order of 10~(-t5imes the mater de)nsity, and, most importantly,it is gauge-dependent.