ac response of a double quantum dot

We calculate the linear response admittance of a double quantum dot in an external time-dependent field. We show how the Kondo resonance peaks evolve with the interdot tunneling amplitude. In the Kondo regime, the real part of the admittance jumps in the vicinity of frequency $\Omega$ equal to the applied dc voltage $\mathrm{eV}$. The imaginary part is linear in the frequency for $\Omega <\mathrm{eV}$. Both features directly reflect the Kondo peaks in the double dot spectral function.