An identity for reproducing kernels in a planar domain and Hilbert-Schmidt Hankel operators.
The Invariant Subspace Problem for Hilbert spaces is a long-standing question and the use of universal operators in the sense of Rota has been an important tool for studying such important problem. In this survey, we focus on Rota’s universal operators, pointing out their main properties and exhibiting some old and recent examples.
Motivated by the relationship between the area of the image of the unit disk under a holomorphic mapping and that of , we study various norms for , where is the Toeplitz operator with symbol . In Theorem , given polynomials and we find a symbol such that . We extend some of our results to the polydisc.