Fractal structures and the large scale distribution of galaxies

Abstract

Galaxy structures are certainly fractal up to a certain crossover scale λ_0. A clear determination of such a scale is still missing. Usually, the conceptual and practical implications of this property are neglected and the structures are only discussed in terms of their global amplitude. Here we present a compact summary of these implications. First, we discuss the problem of the identification of the crossover scale λ_0 and the proper characterization of the scaling. We then consider the implications of these properties with respect to various physical phenomena and to the corresponding characteristic values, i.e. r_0, σ_8, Ω, etc. These implications crucially depend on the value of λ_0, but they are still important for a relatively small value, say λ_0 \approx 50 \hmp. Finally we consider the main theoretical consequences of these results.