Equilibrium Correlations in a Clustering Universe

It is shown that the observed result of two-point galaxy correlation function and three-point correlation function in the universe agrees with a quasi-equilibrium assumption of mass distribution. Utilizing the form of the three-point correlation, we find that the two-point correlation function can be obtained by solving an equation derived from maximizing an entropy under some constraints in a self-gravitating particle model. A generalized non-extensive entropy is also introduced to improve our result.