0 Ju n 19 97 Averaging Inhomogeneous Cosmologies – a Dialogue

The averaging problem for inhomogeneous cosmologies is discussed in the form of a disputation between two cosmologists, one of them (RED) advocating the standard model, the other (GREEN) advancing some arguments against it. Technical explanations of these arguments as well as the conclusions of this debate are given by BLUE. 1. The conjecture about the average flow The standard model which, on some large scale, is defined as a homogeneous and isotropic solution of Einstein’s equations for gravitationally interacting matter, has proved to be remarkably robust against various observational challenges especially of the recent past. It is this robustness together with a list of theoretical and observational arguments which makes it hard to see any need for an alternative to the standard model. Nevertheless, there exist some simple arguments which let the standard model appear dogmatic and a replacement overdue, while most scientific activity in the field is directed towards a consolidation of the standard model. It is fair to say that most of the work, which is directed towards consolidation, is already based implicitly on the assumption that the standard model gives the correct picture. I here scetch a possible dialogue which we can watch without risk of being biassed by some prejudice: we have two people who try to defend Proc. 2 SFB Workshop on Astro–particle physics, Ringberg 1996, Proceedings Series SFB 375/P002 (1997), R. Bender, T. Buchert, P. Schneider and F.v. Feilitzsch (eds.). ‘alternative’ is not meant in the sense of invoking physical laws other than general relativity and making generalizations which depart from the standard kinematical properties of an, on average, homogeneous–isotropic universe. Rather we think at improving on the standard model in its presently employed form. Compare also the discussion in (Ellis et al. 1997).