We consider the Fröhlich Hamiltonian with large coupling constant
.
For initial data of Pekar product form with coherent phonon field and
with the electron minimizing the corresponding energy, we provide
a norm-approximation of the evolution, valid up to times of order
. The
approximation is given in terms of a Pekar product state, evolved through the
Landau–Pekar equations, corrected by a Bogoliubov dynamics taking quantum
fluctuations into account. This allows us to show that the Landau–Pekar
equations approximately describe the evolution of the electron- and one-phonon
reduced density matrices under the Fröhlich dynamics up to times of order
.