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  • On a necessary aspect for the Riesz basis property for indefinite Sturm-Liouville problems
    Kostenko, Aleksej Sergejevič, 1980-
    In [Proc. R. Soc. Edinb., Sect. A, Math. 126, No. 5, 1097--1112 ] H. Volkmer observed that the inequality ▫$$\left( \int_{-1}^{1} \frac{1}{\vert r\vert }\vert f^{\prime }\vert ^{2}dx\right) ^{2} \leq ... K^{2}\int_{-1}^{1}\vert f\vert ^{2}dx\int_{-1}^{1}\vert (\frac{1}{r}f^{\prime })^{\prime }\vert ^{2}dx$$▫ is satisfied with some positive constant ▫$K>0$▫ for a certain class of functions ▫$f$ on $[-1,1]$▫ if the eigenfunctions of the problem ▫$$-y^{\prime \prime }=\lambda r(x)y,~y(-1) = y(1)$$▫ form a Riesz basis of the Hilbert space ▫$L_{\vert r\vert }^{2}(-1,1)$▫. Here, the weight ▫$r\in L^{1}(-1,1)$▫ is assumed to satisfy ▫$xr(x)>0$▫ a.e. on ▫$(-1,1)$▫. The author present two criteria in terms of Weyl-Titchmarsh ▫$m$▫-functions for the Volkmer inequality to be valid. Note that one of these criteria is new even for the classical Hardy-Littlewood-Polya-Everitt (HELP) inequality. Using these results the author improve the result of Volkmer by showing that this inequality is valid if the operator associated with the spectral problem satisfies the linear resolvent growth condition. In particular, the author shows that the Riesz basis property of eigenfunctions is equivalent to the linear resolvent growth if ▫$r$▫ is odd.
    Source: Mathematische Nachrichten. - ISSN 0025-584X (Vol. 287, iss. 14-15, 2014, str. 1710-1732)
    Type of material - article, component part ; adult, serious
    Publish date - 2014
    Language - english
    COBISS.SI-ID - 18026073

source: Mathematische Nachrichten. - ISSN 0025-584X (Vol. 287, iss. 14-15, 2014, str. 1710-1732)

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