Extremal problems in Bergman spaces
by Ferguson, Timothy James, Ph.D., UNIVERSITY OF MICHIGAN, 2011, 78 pages; 3458859

Abstract:

We deal with extremal problems in Bergman spaces. If A P denotes the Bergman space, then for any given functional &phis; ≠ 0 in the dual space (AP)*, an extremal function is a function FAP such that ||F||AP = 1 and Re &phis;(F) is as large as possible.

We give a simplified proof of a theorem of Ryabykh stating that if k is in the Hardy space Hq for 1/ p + 1/q = 1, and the functional &phis; is defined by ff= Dfz kzds, f∈Ap, where σ is normalized Lebesgue area measure, then the extremal function over the space AP is actually in HP.

We also extend Ryabykh's theorem in the case where p is an even integer. Let p be an even integer, and let &phis; be defined as above. Furthermore, let p1 and q1 be a pair of numbers such that q q1 < ∞ and p1 = ( p – 1)q1. Then F ∈ [special characters omitted] if and only if k ∈ [special characters omitted]. For p an even integer, this contains the converse of Ryabykh's theorem, which was previously unknown. We also show that FH if the coefficients of the Taylor expansion of k satisfy a certain growth condition.

Finally, we develop a method for finding explicit solutions to certain extremal problems in Bergman spaces. This method is applied to some particular classes of examples. Essentially the same method is used to study minimal interpolation problems, and it gives new information about canonical divisors in Bergman spaces.

 
AdviserPeter L. Duren
SchoolUNIVERSITY OF MICHIGAN
SourceDAI/B 72-08, p. , Jul 2011
Source TypeDissertation
SubjectsApplied mathematics; Mathematics
Publication Number3458859
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