  The unitary NN-piNN model contains a serious theoretical flaw: unitarity is
obtained at the price of having to use an effective piNN coupling constant that
is smaller than the experimental one. This is but one aspect of a more general
renormalization problem whose origin lies in the truncation of Hilbert space
used to derive the equations. Here we present a new theoretical approach to the
piNN problem where unitary equations are obtained without having to truncate
Hilbert space. Indeed, the only approximation made is the neglect of connected
three-body forces. As all possible dressings of one-particle propagators and
vertices are retained in our model, we overcome the renormalization problems
inherent in previous piNN theories. The key element of our derivation is the
use of convolution integrals that have enabled us to sum all the possible
disconnected time-ordered graphs. We also discuss how the convolution method
can be extended to sum all the time orderings of a connected graph. This has
enabled us to calculate the fully dressed NN one pion exchange potential. We
show how such a calculation can be used to estimate the size of the connected
three-body forces neglected in the new piNN equations. Early indications are
that such forces may be negligible.
