Phase Transitions and Galaxy Clustering

Abstract

The clustering of galaxies is sometimes said to resemble a phase transition from a uniform distribution to an inhomogeneous collection of clusters. We examine how close this resemblance actually is using the cosmological many-body model for galaxy clustering. This model agrees well with the observed galaxy distribution and correlation functions. It also has exact analytic equations of state which can be used to explore its phase transition properties simply and directly. While there are superficial resemblances to a second-order phase transition, this description is modified by the infinite dynamical timescale needed for a hierarchy of clustering to develop at all levels throughout the universe. In an Einstein-deSitter cosmology, a first-order phase transition may occur asymptotically in the infinite future.