  The dependence of cosmological and inflationary parameters on time during the
last 60 e-folds in inflation is investigated using a slow-roll inflation model.
The time dependence of the inflaton field is calculated for the case of chaotic
inflation by a numerical method rather than the familiar approximations. It is
found that the Hubble parameter and the spectral index decrease in the last 60
e-folds. The dependence of the power spectrum of the curvature perturbation on
the size perturbation k is calculated numerically, and it is shown that the
overall constant value of the power spectrum thus determined differs from that
given by the familiar method. However, the k-dependent spectra of the numerical
calculation, the Bessel function approximation, and the familiar Taylor
expansion are all found to be consistent.
