Main Article Content
Let A be a positive operator on a Hilbert space H with 0 < m â¤ A â¤ M, and let X and Y be isometries on H such that X*Y = 0, p > 0, and Î¦ be a 2-positive unital linear map. Define Î = (Î¦(X*AY )Î¦(Y*AY )^(â1)Î¦(Y*AX)^p Î¦(X*AX)^(âp). Several upper bounds for (1/2) |Î + Î*| are established. These bounds complement a recent result on the operator Wielandt inequality.