The concept of essential numerical range of an operator was dened and studied by Stamp i and Williams in 1972. Researchers generalised this idea of essential numerical range to a group of operators to the joint essential ...
Denote by T the bounded linear operator on a complex Hilbert space X and let T = U|T | be any polar decomposition of T with U a partial isometry and |T | = (T ∗T ) 1 2 . Then, the Aluthge transform Te of T is the operator ...