  Time evolution of a black hole lattice universe is simulated. The vacuum
Einstein equations in a cubic box with a black hole at the origin are
numerically solved with periodic boundary conditions on all pairs of opposite
faces. Defining effective scale factors by using the area of a surface and the
length of an edge of the cubic box, we compare them with that in the
Einstein-deSitter universe. It is found that the behaviour of the effective
scale factors is well approximated by that in the Einstein-deSitter universe.
Our result suggests that local inhomogeneities do not significantly affect the
global expansion law of the universe even if the inhomogeneity is extremely
nonlinear.
