  We investigate in a nonperturbative way the dynamics of a correlated quantum
capacitor. We find that the many-body correlations do not disturb the universal
low-frequency relaxation resistance per channel, $R_q(\omega=0) = h/4e^2$
ensured by the Korringa-Shiba rule whereas the interpretation of the quantum
capacitance $C_q$ in terms of the density of states fails when strong
correlations are present. The AC resistance $R_q(\omega)$ shows huge peaks
(with values larger than $h/4e^2$) at $\hbar\omega \approx \pm \Gamma^*$, where
$\Gamma^*$ is the renormalized level broadening. These peaks are merged to a
single one at $\omega=0$ when a finite Zeeman field is applied comparable to
$\Gamma^*$. The observed features of $R_q$, being most evident in the Kondo
regime, are attributed to the generation of particle-hole excitations in the
contacts accomplished by spin-flip processes in the dot.
