MODELING GRAVITATIONAL CLUSTERING WITHOUT COMPUTING GRAVITATIONAL FORCE

The large-scale structure in the universe is believed to have arisen o ut of small, random density perturbations generated in the very early universe that are amplified by gravity. Large and usually intricate N- body simulations are typically employed to model the complex nonlinear dynamics in a self-gravitating medium. We suggest a very simple model that predicts, on large scales, the correct density and velocity dist ributions. The model does not involve an explicit computation of the g ravitational force. It is based on a simple transformation of the vari ables and local conservation laws of mass and generalized linear momen tum. The model demonstrates that the overall appearance of large-scale structure in the universe is explicitly determined by the initial vel ocity field, and it reveals the most significant large-scale effects o f gravity on the formation of structure.