Address.
Department of Mathematics, Ferdowsi
University of Mashhad
P. O. Box 1159, Mashhad 91775, Iran
and
Institute for Studies in Theoretical Physics and Mathematics
(IPM), Iran
E-mail. msalm@@math.um.ac.ir
Abstract.
An operator with infinite dimensional kernel is positive iff it is
a positive scalar times a certain product of three projections.
AMSclassification. 47A05, 47A68.
Keywords. Projection, positive operator, factorization.