ON THE FRACTAL STRUCTURE OF GALAXY DISTRIBUTION AND ITS IMPLICATIONS FOR COSMOLOGY

Two fundamental empirical laws have been established in the analysis o f galaxy space distribution. First, recent analyses have revealed that the three-dimensional distribution of galaxies and clusters is charac terized by large-scale structures and huge voids: such a distribution shows fractal correlations up to the limits of the available samples. This has confirmed the earlier de Vaucouleurs power-law density - dist ance relation, now corresponding to a fractal structure with dimension D approximate to 2, at least, in the range of scales similar to 1 div ided by 200 Mpc (H-0 = 55 km/sec/Mpc). An eventual cut-off towards hom ogenization has not been yet identified. Second, since Hubble's discov ery, the linear redshift-distance law has been well established within 200 Mpc and also much deeper. The co-existence of these laws within t he same scales is a challenge for the standard cosmology, where the li near Hubble law is a strict consequence of homogeneity of the expandin g universe. This puzzle is now sufficiently strong to raise doubts for the standard cosmology.