  Using a time-dependent Anderson Hamiltonian, a quantum dot with an ac voltage
applied to a nearby gate is investigated. A rich dependence of the linear
response conductance on the external frequency and driving amplitude is
demonstrated. At low frequencies the ac potential produces sidebands of the
Kondo peak in the spectral density of the dot, resulting in a logarithmic
decrease in conductance over several decades of frequency. At intermediate
frequencies, the conductance of the dot displays an oscillatory behavior due to
the appearance of Kondo resonances of the satellites of the dot level. At high
frequencies, the conductance of the dot can vary rapidly due to the interplay
between photon-assisted tunneling and the Kondo resonance.
