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On the Range of the Aluthge Transform
Authors:Guoxing Ji  Yongfeng Pang  Ze Li
Affiliation:(1) College of Mathematics and Information Science, Shaanxi Normal University, Xian, 710062, People’s Republic of China
Abstract:Let $$mathcal{B}{left( mathcal{H} right)}$$ be the algebra of all bounded linear operators on a complex separable Hilbert space $$mathcal{H}{text{.}}$$ For an operator $$T in mathcal{B}{left( mathcal{H} right)}{text{,}}$$ let $$ ifmmodeexpandaftertildeelseexpandafter~fi{T} = |T|^{{frac{1}{2}}} U|T|^{{frac{1}{2}}}$$ be the Aluthge transform of T and we define $$Delta {left( T right)} = ifmmodeexpandaftertildeelseexpandafter~fi{T} $$ for all $$ in mathcal{B}{left( mathcal{H} right)},$$ where T = U|T| is a polar decomposition of T. In this short note, we consider an elementary property of the range $$ R{left( Delta right)} = {left{ { ifmmodeexpandaftertildeelseexpandafter~fi{T}:T in mathcal{B}{left( mathcal{H} right)}} right}} $$ of Δ. We prove that R(Δ) is neither closed nor dense in $$mathcal{B}{left( mathcal{H} right)}.$$ However R(Δ) is strongly dense if $$mathcal{H}$$ is infinite dimensional. An erratum to this article is available at .
Keywords:Primary 47A15  Secondary 47B20
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