Abstract:
The embedding constants for the Sobolev spaces ˚Wn2[0;1]↪˚Wk2[0;1] (0⩽) are studied. A relationship between the embedding constants and the norms of the functionals f\mapsto f^{(k)}(a) in the space \mathring W^n_2[0;1] is given. An explicit form of the functions g_{n,k}\in \mathring W^n_2[0;1] on which these functionals attain their norm is found. These functions are also extremals for the embedding constants. A connection between the embedding constants and the Legendre polynomials is put forward. A detailed study is made of the embedding constants for k=3 and k=5: explicit formulas for extreme points are obtained, global maximum points calculated, and the values of the sharp embedding constants is given. A link between the embedding constants and some class of spectral problems with distribution coefficients is established.
Key words and phrases:
Sobolev spaces, embedding constants, Legendre polynomials.
The results of §§2 and 3 were obtained with the support of the Russian Foundation for Basic Research (grant no. 19-01-00240) and the results of §§4–6 were obtained with the support of the Russian Science Foundation (grant no. 17-11-01215).
Citation:
I. A. Sheipak, T. A. Garmanova, “An explicit form for extremal functions in the embedding constant problem for Sobolev spaces”, Tr. Mosk. Mat. Obs., 80, no. 2, MCCME, M., 2019, 221–246; Trans. Moscow Math. Soc., 80 (2019), 189–210
\Bibitem{SheGar19}
\by I.~A.~Sheipak, T.~A.~Garmanova
\paper An explicit form for extremal functions in the embedding constant problem for Sobolev spaces
\serial Tr. Mosk. Mat. Obs.
\yr 2019
\vol 80
\issue 2
\pages 221--246
\publ MCCME
\publaddr M.
\mathnet{http://mi.mathnet.ru/mmo628}
\elib{https://elibrary.ru/item.asp?id=43277171}
\transl
\jour Trans. Moscow Math. Soc.
\yr 2019
\vol 80
\pages 189--210
\crossref{https://doi.org/10.1090/mosc/292}
\scopus{https://www.scopus.com/record/display.url?origin=inward&eid=2-s2.0-85083777138}
Linking options:
https://www.mathnet.ru/eng/mmo628
https://www.mathnet.ru/eng/mmo/v80/i2/p221
This publication is cited in the following 5 articles:
T. A. Garmanova, I. A. Sheipak, “Exact estimates for higher order derivatives in Sobolev spaces”, Moscow University Mathematics Bulletin, 79:1 (2024), 1–10
D. D. Kazimirov, I. A. Sheipak, “Exact Estimates of Functions in Sobolev Spaces with Uniform Norm”, Dokl. Math., 2024
T. A. Garmanova, I. A. Sheipak, “Relationship Between the Best L_p Approximations of Splines by Polynomials with Estimates of the Values of Intermediate Derivatives in Sobolev Spaces”, Math. Notes, 114:4 (2023), 625–629
T. A. Garmanova, I. A. Sheipak, “On Sharp Estimates of Even-Order Derivatives in Sobolev Spaces”, Funct. Anal. Appl., 55:1 (2021), 34–44
T. A. Garmanova, “Estimates of Derivatives in Sobolev Spaces in Terms of Hypergeometric Functions”, Math. Notes, 109:4 (2021), 527–533