Let
A=(Aij)Ni,j=1Cn×n be a
block irreducible matrix with nonsingular
diagonal blocks,
v=(vi)CN be a positive vector, and let
Formula Not Shown Under these assumptions, necessary and sufficient conditions for
A to be singular are obtained based on a
block generalization of Wielandts lemma. The pointwise case (
N=n) of irreducible matrices with
nonstrict generalized
diagonal dominance is treated separately.