  Starting from the matrix elements of the nucleon-nucleon interaction in
momentum space we present a method to derive an operator representation with a
minimal set of operators that is required to provide an optimal description of
the partial waves with low angular momentum. As a first application we use this
method to obtain an operator representation for the Argonne potential
transformed by means of the unitary correlation operator method and discuss the
necessity of including momentum dependent operators. The resulting operator
representation leads to the same results as the original momentum space matrix
elements when applied to the two-nucleon system and various light nuclei. For
applications in fermionic and antisymmetrized molecular dynamics, where an
operator representation of a soft but realistic effective interaction is
indispensable, a simplified version using a reduced set of operators is given.
