On the similarity of powers of operators with flag structure.

Let \mathrm {L}^2_a(\mathbb {D}) be the classical Bergman space and let M_h denote the operator of multiplication by a bounded holomorphic function h. Let B be a finite Blaschke product of order n. An open question proposed by R. G. Douglas is whether the operators M_B on \mathrm {L}^2_a(\mathbb {D}) similar to \oplus _1^n M_z on \oplus _1^n \mathrm {L}^2_a(\mathbb {D})? The question was answered in the affirmative, not only for Bergman space but also for many other Hilbert spaces with reproducing kernel. Since the operator M_z^* is in Cowen-Douglas class B_1(\mathbb {D}) in many cases, Douglas question can be reformulated for operators in B_1(\mathbb {D}), and the answer is affirmative for many operators in B_1(\mathbb {D}). A natural question occurs for operators in Cowen-Douglas class B_n(\mathbb {D}) (n>1). In this paper, we investigate a family of operators, which are in a norm dense subclass of Cowen-Douglas class B_2(\mathbb {D}), and give a negative answer. [ABSTRACT FROM AUTHOR]