4 papers
The Local Operator Moment Problem on
Raul E. Curto, Abderrazzak Ech-charyfy, Hamza El Azhar +1
We study the connections between operator moment sequences of self-adjoint operators on a complex Hilbert space a…
Propagation Phenomena for Operator-Valued Weighted Shifts
Raul E. Curto, Abderrazzak Ech-charyfy, Hamza El Azhar +1
This paper is devoted to the study of propagation phenomena for --hyponormal, quadratically hyponormal, and cubically hyponormal operator-valued weighted shifts. \ First, we sho…
A Combinatorial Formula for Recursive Operator Sequences and Applications
Raul E. Curto, Abderrazzak Ech-charyfy, Kaissar Idrissi +1
We study sequences of bounded operators \((T_n)_{n \ge 0}\) on a complex separable Hilbert space \(\mathcal{H}\) that satisfy a linear recurrence relation of the form $$ T_{n+r} =…
The Square Root Problem and Subnormal Aluthge Transforms of Recursively Generated Weighted Shifts
Raul E. Curto, Hamza El Azhar, Youssef Omari +1
For recursively generated shifts, we provide definitive answers to two outstanding problems in the theory of unilateral weighted shifts: the Subnormality Problem ({\bf SP}) (relate…