A characterization of extremal elements in some linear problems
Ural mathematical journal, Tome 3 (2017) no. 2, pp. 22-32
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We give a characterization of elements of a subspace of a complex Banach space with the property that the norm of a bounded linear functional on the subspace is attained at those elements. In particular, we discuss properties of polynomials that are extremal in sharp pointwise Nikol'skii inequalities for algebraic polynomials in a weighted $L_q$-space on a finite or infinite interval.
Keywords:
Complex Banach space, Bounded linear functional on a subspace, Pointwise Nikol'skii inequality.
Mots-clés : Algebraic polynomial
Mots-clés : Algebraic polynomial
@article{UMJ_2017_3_2_a3,
author = {Vitalii V. Arestov},
title = {A characterization of extremal elements in some linear problems},
journal = {Ural mathematical journal},
pages = {22--32},
publisher = {mathdoc},
volume = {3},
number = {2},
year = {2017},
language = {en},
url = {http://geodesic.mathdoc.fr/item/UMJ_2017_3_2_a3/}
}
Vitalii V. Arestov. A characterization of extremal elements in some linear problems. Ural mathematical journal, Tome 3 (2017) no. 2, pp. 22-32. http://geodesic.mathdoc.fr/item/UMJ_2017_3_2_a3/