  In the recent publication arXiv:1410.8860 the spin vertex was introduced as a
new approach for computing three-point functions in N = 4 SYM. In this note we
consider the BMN limit of the spin vertex for scalar excitations and show that
it reproduces the string vertex in the light-cone string field theory which
describes the string interactions in the pp-wave background at the leading
order of BMN expansion. This is achieved by introducing a polynomial
representation for the spin vertex. We derive the Neumann coefficients from the
spin vertex at weak coupling and show they match with the Neumann coefficients
from the string field theory.
