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Hierarchical Clustering in Scale-Free Universes: Caption

These two animations show a projection of matter-density in two numerical simulations of gravitational clustering in an expanding universe. They represent the time evolution of the matter in a fixed volume of each simulated universe. Millions of particles of pure dark matter were tracked in these 3-dimensional simulations, but the movies presented here are 2-D projections of the resulting data.

Two distinct though related algorithmic approaches to modelling were attempted.

Gravitational instability with n=-2, "scale-Free" spectrum; P3M code; 128^3 particles

In the first simulation, a P3M code was run on NCSA's Convex C-3880, using 2 millions particles, with a power spectrum corresponding to P = 1/K^2.

Gravitational instability with n=0, "scale-free" spectrum; PM code; 256^3 particles on a 512^3 mesh

The second simulation was more computationally intensive. 16 million particles were used and the calculations were performed on NCSA's CM-5. The starting conditions or"initial power spectrum" were also different in that P = a constant.

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Copyright, (c) 1995: Board of Trustees, University of Illinois

NCSA. Last modified, 10/11/95