  We develop a local realist analysis of parametric down conversion, based on
the recognition that the pump field, instead of down converting spontaneously,
does so through its nonlinear coupling with a real zeropoint, or "vacuum"
electromagnetic field. The theory leads tothe prediction of a new phenomenon -
that, in addition to the main down-conversion rainbow, there is a satellite
rainbow, whose intensity is about 3 per cent of the main one. Confirmation of
this prediction will call seriously into question the current description of
the light field in terms of photons.
  The present article extends the analysis of its predecessors (this archive,
numbers 9711029 and 9712001) to take account of the pump's polarization>
