Y. Esstafa

Hahn-Type Orthogonality for the Resolvent Delta Operator $\mathscr L=D(I-D)^{-1}$

We investigate orthogonality under the shift-invariant resolvent delta operator $\mathscr L=D(I-D)^{-1}$. First, we prove a rigidity theorem: a monic orthogonal polynomial sequence is $\mathscr L$-Appell if and only if it is a translated Laguerre sequence. We then move beyond the Appell setting and show that the diagon...