#### Document Type

Article

#### Department/Program

Mathematics

#### Journal Title

Linear Algebra and Its Applications

#### Pub Date

2009

#### Volume

431

#### Issue

12

#### First Page

2336

#### Abstract

Let B(H) be the algebra of bounded linear operator acting on a Hilbert space H (over the complex or real Held). Characterization is given to A(1), ... , A(k) is an element of B(H) such that for any unitary operators U(1), ... , U(k), Sigma(k)(j=1) U(j)*A(j)U(j) is always in a special class S of operators such as normal operators, self-adjoint operators, unitary operators. As corollaries, characterizations are given to A is an element of B(H) such that complex, real or nonnegative linear combinations of operators in its unitary orbit u(A) = {U*AU : Uunitary} always lie in S. (c) 2009 Elsevier Inc. All rights reserved.

#### Recommended Citation

Li, C. K., & Poon, Y. T. (2009). The sum of unitary similarity orbits containing only special operators. Linear Algebra and its Applications, 431(12), 2336-2345.

#### DOI

10.1016/j.laa.2009.03.010