Dark matter, about which little is known except that it exists, is theorized to be the seed for the growth of structure in the universe. The matter of everyday life (protons, neutrons, and electrons) forms galaxies, and galactic clusters according to where the early dark matter structures formed. Beginning with a random distribution, the dark matter structures tend to be built by gravitational attraction. Rapidly moving particles called "hot dark matter" (HDM) tend to destroy the gravitationally built structures. If the particles are slow-moving they are called "cold dark matter" (CDM). At present (2001), CDM structure growth is much more consistent with astronomical observations than HDM.

Growth of large scale structure due to CDM is demonstrated in the toy-model simulation below, based on an algorithm by K&S, a version of which can be downloaded here. Researchers more commonly present simulations in 3D. The physics of the toy-model is "nearest-neighbor gravity," horizon growth, and a CDM-HDM parameter.




dsmith@scsu.edu, South Carolina State University, 12/30/2012