Converse characterization of the essential approximate point spectrum for elliptic and double parabolic Blaschke products
Converse characterization of the essential approximate point spectrum for elliptic and double parabolic Blaschke products
Let be an elliptic or double parabolic Blaschke product of degree , and let be the weighted composition operator on the disc algebra associated with and a weight . Consider the set of moduli of scalars whose circles lie in the upper semi-Fredholm spectrum:
Converse characterization conjecture. The set is at most countable and its only accumulation point, if any, is .
The surrounding discussion presents this as the converse to the preceding theorem for finite Blaschke products. The supplied text does not establish the converse, so its resolution remains open.
Sources & referencesView supporting material
Primary source
Arkady Kitover and Mehmet Orhon, “Spectrum of weighted composition operators. Part XI. The essential spectra of some weighted composition operators on the disc algebra”, arXiv:2503.17516 (2025).
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