  We study the large N reduced model of D-dimensional Yang-Mills theory with
special attention to dynamical aspects related to the eigenvalues of the N by N
matrices, which correspond to the space-time coordinates in the IIB matrix
model. We first put an upper bound on the extent of space time by perturbative
arguments. We perform a Monte Carlo simulation and show that the upper bound is
actually saturated. The relation of our result to the SSB of the U(1)^D
symmetry in the Eguchi-Kawai model is clarified. We define a quantity which
represents the uncertainty of the space-time coordinates and show that it is of
the same order as the extent of space time, which means that a classical
space-time picture is maximally broken. We develop a 1/D expansion, which
enables us to calculate correlation functions of the model analytically. The
absence of an SSB of the Lorentz invariance is shown by the Monte Carlo
simulation as well as by the 1/D expansion.
