Nonequilibrium Kondo

We consider a quantum dot connected to Fermi liquid leads in the Kondo regime, when ac voltages are applied to the leads and also to the dot. For temperatures well-below the Kondo temperature ($T_K$) we identify an effective time-dependent Hamiltonian that contains all the relevant (in the renormalization group sense) operators. With this as the starting point, we solve the ac transport problem by including the role of leading irrelevant operators. The theoretical results are compared to the recent experimental observation by Kogan {\it et al.}~[Science~\bf{304}, 1293 (2004)] of satellite peaks in the differential conductance of a single electron transistor in the Kondo regime.