  In this paper, we analyze the effects of expansion on large scale structure
formation in our Universe. We do that by incorporating a cosmological constant
term in the gravitational partition function. This gravitational partition
function with a cosmological constant is used for analyzing the thermodynamics
of this system. We analyze the virial expansion for this system, and obtain its
equation of state. It is observed that the generalization of this equation of
state is like the Van der Waals equation. We also analyze a gravitational phase
transition in this system using the mean field theory. We construct the cosmic
energy equation for this system of galaxies, and discuss its consequences. We
obtain and analyze the distribution function for this system, using the
gravitational partition function. We also compare the results obtained in this
paper with the observational data.
