  We study quenches of the interaction and electron-phonon coupling parameter
in the Hubbard-Holstein model, using nonequilibrium dynamical mean field
theory. The calculations are based on a generalized Lang-Firsov scheme for
time-dependent interactions or externally driven phonons, and an approximate
strong-coupling impurity solver. The interaction quench calculations reveal the
phonon-assisted decay of excess doublons, while the quenches of the
electron-phonon coupling lead to persistent oscillations of the phonons and to
a phonon-enhanced doublon production.
