  We examine the validity of the weak coupling spin-susceptibility "glue"
approximation (SSGA) in a two-dimensional Hubbard model for cuprates. For
comparison, we employ the well-established dynamical cluster approximation
(DCA) with a quantum Monte Carlo algorithm as a cluster solver. We compare the
leading eigenvalues and corresponding eigenfunctions of the DCA and SSGA
pairing matrices. For realistic model parameters, we find that the SSGA fails
to capture the leading pairing symmetries seen in the DCA. Furthermore, when
the SSGA is improved through the addition of a term with d-wave symmetry, the
strength of this additional term is found to be larger than that of the "glue"
approximation.
