On product of projections

Mohammad Sal Moslehian

  Department of Mathematics, Ferdowsi University of Mashhad P. O. Box 1159, Mashhad 91775, Iran


Institute for Studies in Theoretical Physics and Mathematics (IPM), Iran

E-mail. msalm@@math.um.ac.ir

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.