This paper relates questions about factorizations of positive matrices
to properties of analytic reproducing kernel Hilbert spaces. In parti
cular the question of when the polynomials are dense in a reproducing
kernel Hilbert space is related to the factoring of an associated posi
tive matrix into the form UU where U is an upper triangular matrix. A
n emphasis is placed on factorization and reproducing kernel methods a
s opposed to function theoretic methods.