  Within a two component approach to high Tc copper oxides including polaronic
couplings, we identify the pseudogap phase as the onset of polaron ordering.
This ordering persists in the superconducting phase. A huge isotope effect on
the pseudogap onset temperature is predicted and in agreement with experimental
data. The anomalous temperature dependence of the mean square copper oxygen ion
displacement observed above, at and below Tc stems from an s-wave
superconducting component of the order parameter, whereas a pure d-wave order
parameter alone can be excluded.
