The \(n\)-width of the unit ball of \(H^ p\). (English) Zbl 0746.41026
From the authors’ abstract: ‘Let \(E\) be a compact subset of the open unit disc \(\Delta\) and let \(H^ q\) be the Hardy space of analytic functions \(f\) on \(\Delta\) for which \(| f|^ q\) has a harmonic majorant. We determine the value of the Kolmogorov, Gel’fand, and linear \(n\)-widths in \(L^ p(E,\mu)\) of the restriction to \(E\) of the unit ball of \(H^ q\) when \(p\leq q\) or when \(1\leq q<p<\infty\) and \(E\) is “small”’.
Reviewer: G.D.Taylor (Fort Collins)
MSC:
| 41A46 | Approximation by arbitrary nonlinear expressions; widths and entropy |
| 30E10 | Approximation in the complex plane |
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