Abstract
We expand the class of deviation sequences for which the problem on the existence of an element of a Banach space with these deviations from a system of nested subspaces is solved positively regardless of the space and the system of subspaces. This result is used to narrow the gap between the weak asymptotics constants in S. V. Konyagin’s theorem on the existence of an element whose deviations are asymptotically close to given ones.
References
S. N. Bernstein, “On an inverse problem of the theory of best approximation of continuous functions,” in Collection of Works (Izd. Akad. Nauk SSSR, Moscow, 1954), Vol. 2, pp. 292–294 [in Russian].
A. F. Timan, Theory of Approximation of Functions of a Real Variable. (Fizmatgiz, Moscow, 1960) [in Russian].
V. N. Nikol’skii, “Some properties of reflexive spaces,” Kalinin. Gos. Ped. Inst. Ucen. Zap. 29, 121–125 (1963).
I. S. Tyuremskikh, “The \((B)\)-property of Hilbert spaces,” Kalinin. Gos. Ped. Inst. Ucen. Zap. 39, 53–64 (1964).
H. S. Shapiro, “Some negative theorems of approximation theory,” Michigan Math. J. 11 (3), 211–217 (1964).
I. S. Tyuremskikh, “A certain theorem of S. N. Bernstein,” Kalinin. Gos. Ped. Inst. Ucen. Zap. 52, 123–129 (1967).
P. A. Borodin, “On the existence of an element with given deviations from an expanding system of subspaces,” Math. Notes 80 (5), 621–630 (2006).
S. V. Konyagin, “Deviation of elements of a Banach space from a system of subspaces,” Proc. Steklov Inst. Math. 284, 204–207 (2014).
Acknowledgments
The author thanks P. A. Borodin for valuable remarks.
Funding
This work was financially supported by the Russian Science Foundation (project 23-71-30001, https://rscf.ru/en/project/23-71-30001/) at Lomonosov Moscow State University.
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Translated from Matematicheskie Zametki, 2023, Vol. 114, pp. 780–788 https://doi.org/10.4213/mzm13982.
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Skvortsov, Y.A. On the Existence of an Element with Given Deviations from an Expanding System of Subspaces. Math Notes 114, 949–956 (2023). https://doi.org/10.1134/S0001434623110299
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DOI: https://doi.org/10.1134/S0001434623110299