  The exact nonlinear response of noninteracting (Bloch) electrons is examined
within a nonequilibrium formalism on the infinite-dimensional hypercubic
lattice. We examine the effects of a spatially uniform, but time-varying
electric field (ignoring magnetic-field effects). The electronic Green's
functions, Wigner density of states, and time-varying current are all
determined and analyzed. We study both constant and pulsed electric fields,
focusing on the transient response region. These noninteracting Green's
functions are an important input into nonequilibrium dynamical mean field
theory for the nonlinear response of strongly correlated electrons.
