Conjecture on the distance formula and strong exposedness of the functions fβf_\beta

From papers

Let A1A^1 be the Bergman space, let (A1)(A^1)^\perp denote its annihilator in the relevant dual space, let CC denote the subspace of constant functions, and let φβ\varphi_\beta and fβf_\beta be the functions defined in the paper for 2<β<0-2<\beta<0. For a point xx and subset EE of a normed space, write d(x,E)d(x,E) for the distance from xx to EE. Distance and exposedness conjecture. For all 2<β<0-2<\beta<0,

d(φβ,(A1)+C)=2πsin(βπ2)β+2.d(\varphi_\beta,(A^1)^\perp+C)=\frac{2}{\pi}\frac{|\sin(\frac{\beta\pi}{2})|}{\beta+2}.

In particular, the functions fβf_\beta are strongly exposed for all such β\beta. This conjecture extends the established strong exposedness result for 1<β<0-1<\beta<0 and is motivated by the asymptotic sharpness of the distance inequality as β\beta decreases to 2-2; its resolution for the full interval remains open in the supplied text.

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Sources & referencesView supporting material

Primary source

Paul Beneker and Jan Wiegerinck, “Strongly exposed points in the ball of the Bergman space”, arXiv:math/0208234 (2002).

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