  The type IIB matrix model is a conjectured nonperturbative formulation of
superstring theory. Recently the Lorentzian version of the model has been
studied by Monte Carlo simulation, and it has been shown that only three out of
nine spatial directions start to expand after a critical time. We extend this
work by investigating the expanding behavior for much longer time. We find that
the 3d space expands exponentially for some period of time, which may be
interpreted as inflation. We also simulate a simplified model, which is
expected to capture some qualitative features of the original model at much
later times. We observe that the exponential expansion eventually changes into
a power-law t^(1/2) behavior, which agrees with the expanding behavior of the
Friedmann-Robertson-Walker (FRW) universe in the radiation dominated era.
