We investigate the finite-frequency thermal transport through a quantum dot
subject to strong interactions, by providing an exact, nonperturbative
formalism that allows us to carry out a systematic analysis of the thermopower
at any frequency. Special emphasis is put on the dc and high-frequency limits.
We demonstrate that, in the Kondo regime, the ac thermopower is characterized
by a universal function that we determine numerically.Comment: 8 pages, 8 figure
