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E. Bertschinger (Department of Physics, MIT)
I will review the numerical evidence that hierarchical clustering of collisionless dark matter produces virialized halos with a universal radial profile with two power laws and a break. This result, first presented in 1996 by Navarro, Frenk, and White, has found many applications in cosmological theory and data analysis. Its origin is still poorly understood. Naive spherical infall predicts a steeper inner profile whose slope depends on the initial power spectrum. Angular momentum flattens the inner profile toward the NFW shape but should not erase the dependence on initial conditions. Full N-body simulations suggest that the memory of initial conditions is erased aside from a statistical effect on the ratio of the virial radius to the break radius. A promising possibility is that the stochastic effects of mergers and substructure lead to noise-driven evolution described by a Fokker-Planck equation. The dissipative effects of such evolution may erase memory of initial conditions and drive dark matter profiles toward a universal form. This talk will summarize theoretical ideas and present new results concerning the origin of the universal profile.
This work is supported by the National Science Foundation through grant AST-9803137.