Abstract. Let R and S be two operators on a Hilbert space. We discuss the link between the subscalarity of RS and SR. As an application, we show that backward Aluthge iterates of hyponormal operators and p-quasihyponormal operators are subscalar.
Introduction.Let H be a Hilbert space and L(H) be the algebra of bounded linear operators on H. We write σ(T ) for the spectrum of T .In [14], M. Putinar showed that a hyponormal operator has a scalar extension which means that it is similar to the restriction to an invariant subspace of a (generalized) scalar operator (in the sense of Colojoarǎ-Foiaş). This was extended to w-hyponormal operators by E. Ko [10].A bounded linear operator S on H is called scalar of order m if it has a spectral distribution of order m, i.e., if there is a continuous unital morphism of topological algebras Φ : C