© 1996 by London Mathematical Society
© The London Mathematical Society
Vector Majorization Via Hessenberg Matrices
Department of Mathematics, University of Wisconsin Madison, WI 53706, USA
Department of Mathematics Education, Kyungpook University Taegu 702-701, Republic of Korea
Received 12 April 1994.
In this paper it is proved that, for real n-vectors x and y, x is majorized by y if and only if x = PHQy for some permutation matrices P, Q, and for some doubly stochastic matrix H which is a direct sum of doubly stochastic Hessenberg matrices. This result reveals that any n-vector which is majorized by a vector y can be expressed as a convex combination of at most (n2 – n + 2)/2 permutations of y.
First author's research partially supported by NSF grant DMS-9123318. Second author supported by a grant from TGRC-Kosef under the international cooperation program. This paper was completed while the second author was visiting the University of Wisconsin at Madison.