[1] Carnegie Mellon Univ, Bruce & Astrid McWilliams Ctr Cosmol, Pittsburgh, PA 15213 USA
[2] Carnegie Mellon Univ, Dept Phys, Pittsburgh, PA 15213 USA
[3] Carnegie Mellon Univ, Inst Robot, Pittsburgh, PA 15213 USA
[4] Heidelberger Inst Theoret Studien, D-69118 Heidelberg, Germany
[5] Heidelberg Univ, Zentrum Astron, Astron Recheninst, D-69120 Heidelberg, Germany
[6] Pittsburgh Supercomp Ctr, Pittsburgh, PA 15213 USA
[7] Univ Washington, Dept Phys, Seattle, WA 98195 USA