We introduce a new variant of zero forcing - signed zero forcing. The classical zero forcing number provides an upper bound on the maximum nullity of a matrix with a given graph (i.e. zero-nonzero pattern). Our new variant provides an analo- gous bound for the maximum nullity of a matrix with a given sign pattern. This allows us to compute, for instance, the maximum nullity of a Z-matrix whose graph is L(K_{n}), the line graph of a clique.
@article{arxiv.1307.2198,
title = {Zero forcing for sign patterns},
author = {Felix Goldberg and Abraham Berman},
journal= {arXiv preprint arXiv:1307.2198},
year = {2013}
}