Fractal structures and the large scale distribution of galaxies

Galaxy structures are certainly fractal up to a certain crossover scale λ0. A clear determination of sum 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 λ0 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, σ0, Ω, etc. These implications crucially depend on the value of λ0, but they are still import ant for a relatively small value, say λ0 ≈ 50h− Mpc. Finally we consider the main theoretical consequences of these results.