Cosmological Nbody simulations with a treecode
Abstract
Evolution of gravitationally interacting Nbody systems in the universe is numerically studied. The Nbody method is based on the hierarchical tree algorithm and the fully periodic boundary condition is implemented by applying the Ewald method. All of 262,144 particles were used in total, which are initially distributed to represent scalefree power spectra of density fluctuations P(k)proportional to k^{n,} with n = 2, 1, 0 and 1. The subsequent evolution is followed in both flat and open universes. With this large number of particles, the discretized system can represent the initial linear phase, in good agreement with analytic theory. Dynamics in the strongly nonlinear regime depends on both the spectral index n and the density parameter Omega. In Omega = 1 universes, evolution of twopoint correlation functions (xi) for (xi) greater than or approx. 100 agrees with the similarity solutions. In the weakly nonlinear regimes, the growth rate of density fluctuations sensitively depends on n.
 Publication:

NASA STI/Recon Technical Report N
 Pub Date:
 March 1990
 Bibcode:
 1990STIN...9111638S
 Keywords:

 Computerized Simulation;
 Cosmology;
 Gravitational Fields;
 Many Body Problem;
 Trees (Mathematics);
 Algorithms;
 Boundary Conditions;
 Power Spectra;
 Universe;
 Astrophysics