Koji Uryu, Antonios Tsokaros
We present a new code, named COCAL - Compact Object CALculator, for the
computation of equilibriums and quasiequilibrium initial data sets of single or
binary compact objects of all kinds. In the cocal code, those solutions are
calculated on one or multiple spherical coordinate patches covering the initial
hypersurface up to the asymptotic region. The numerical method used to solve
field equations written in elliptic form is an adaptation of self-consistent
field iterations in which Green's integral formula is computed using multipole
expansions and standard finite difference schemes. We extended the method so
that it can be used on a computational domain with excised regions for a black
hole and a binary companion. Green's functions are constructed for various
types of boundary conditions imposed at the surface of the excised regions for
black holes. The numerical methods used in cocal are chosen to make the code
simpler than any other recent initial data codes, accepting the second order
accuracy for the finite difference schemes. We perform convergence tests for
time symmetric single black hole data on a single coordinate patch, and binary
black hole data on multiple patches. Then, we apply the code to obtain
spatially conformally flat binary black hole initial data using boundary
conditions including the one based on the existence of equilibrium apparent
horizons.
View original:
http://arxiv.org/abs/1108.3065
No comments:
Post a Comment