On the fractal structure of the universe: methods, results and theoretical implication

TL;DR

This paper reviews the fractal nature of galaxy distribution, discusses methodological approaches that do not assume homogeneity, and explores the theoretical implications for galaxy formation models, including the concept of bias.

Contribution

It introduces alternative analysis methods for fractal properties in galaxy distribution and discusses their implications for galaxy formation theories.

Findings

Galaxy distribution exhibits fractal properties over certain scales.

Standard methods may overlook fractal features due to homogeneity assumptions.

Revisions to the concept of bias are necessary in light of fractal analysis.

Abstract

The fact that galaxy distribution exhibits fractal properties is well established since twenty years. Nowadays, the controversy concerns the range of the fractal regime, the value of the fractal dimension and the eventual presence of a cross-over to homogeneity. Fractal properties maybe studied with methods which do not assume homogeneity a priori as the standard statistical methods do. We show that complementary to the adoption of new methods of analysis there are important theoretical implications for the usual scenario of galaxy formation. For example, we focus on the concept of bias and we show that it needs a basic revision even if future redshift surveys will be able to identify an eventual tendency to homogenization.