We extend the classical Penon-Frobenius theorem to matrices with some negat
ive entries. We study the cone of matrices that has the matrix of 1's (ee(t
)) as the central ray, and such that any matrix inside the cone possesses a
Perron-Frobenius eigenpair. We also find the maximum angle of any matrix w
ith ee(t) that guarantees this property. (C) 2001 Elsevier Science Inc. All
rights reserved.