Some students of Walter saw mass segregation when they put in two species. The odd part was that they saw the small particles sink to the center, and the large particles get spewn out. I don't really see a way to put in two species without introducing small scale power, but I repeated the experiment with Walter's code. 1001 particles, m and 10m masses. Below is a plot (times 0,10,20,90 in arbitrary units). The windup is well lost by the end, the thing is virialized, but there's no mass segregation. Or if there is a smaaaaall hint of one, it is the smaller particles on the outside. Because of the local density fluctuations, it looks like each little guy has basically stapled itself to a large guy, i.e. each heavy-light pair collapsed together instantly, and then behaved as one particle. I will play around and see if I do m and 1.05m whether things behave qualitatively differently. Click on the picture to see it bigger/better.
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Okay, I just repeated the experiment with m, and 1.1 m. In this plot the times are at (0,20,30,90) in arbitrary units. We do not get the composite particle behavior any longer, but it looks to me like the particles basically remain interleaved. At the final output, there is some "segregation" that can be seen in the stair-stepping of the density profile, but no evidence of inside/ouside mass segregation as far as I can see. I can't be sure, but this might be again because the initial condition does not have a smooth mass density profile, it's lumpy. Here's the plot (click it).
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