11,767 research outputs found
Quaternionic Hankel operators and approximation by slice regular functions
In this paper we study Hankel operators in the quaternionic setting. In
particular we prove that they can be exploited to measure the
distance of a slice function from the space of bounded slice
regular functions.Comment: 19 page
Approximation numbers of weighted composition operators
We study the approximation numbers of weighted composition operators
on the Hardy space on the unit disc. For
general classes of such operators, upper and lower bounds on their
approximation numbers are derived. For the special class of weighted lens map
composition operators with specific weights, we show how much the weight
can improve the decay rate of the approximation numbers, and give sharp upper
and lower bounds. These examples are motivated from applications to the
analysis of relative commutants of special inclusions of von Neumann algebras
appearing in quantum field theory (Borchers triples).Comment: 35 pages, no figures. Some typos removed, minor improvements in
presentation, updated reference
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