WHATEVER HAPPENED TO THE DYER-ROEDER DISTANCE?

摘要

The Universe is not completely homogeneous. Even if it is sufficiently so on large scales, it is very inhomogeneous at small scales, and this has an effect on light propagation, so that the distance as a function of redshift, which in many cases is defined via light propagation, can differ from the homogeneous case. Simple models can take this into account. One such model is known as the Dyer-Roeder distance. I sketch the history of this model and some applications, then suggest some reasons why it is still relatively obscure.