A general theorem on the existance of lipshitz retractions on certain surfaces was proved.<br> As a corollary, a lipshitz $\varepsilon$-selection on the set of generalised rational functions was constructed. Several results, concerning the problem of existance of continuous selections from the operator of generalised rational approximation in $L_p$, $0<p\le\infty$ spaces were obtained. It was proved that pseudodimension of any set is greater or equal than its topological dimension.
Main publications:
Lipshitsevost retraktsii i operator obobschennogo ratsionalnogo priblizheniya // Fundament. i prikl. matem., 2000, # 4, s. 1205–1220.
Ravnomernaya nepreryvnost obobschennykh ratsionalnykh priblizhenii // Matematicheskie zametki, 2002, t. 71, # 2, s. 261–270.
Otsenka snizu psevdorazmernosti cherez topologicheskuyu // Matematicheskie zametki, 2001, t. 70, # 1, s. 155–156.
Yu. V. Malykhin, K. S. Ryutin, “The Product of Octahedra is Badly Approximated in the $\ell_{2,1}$-Metric”, Math. Notes, 101:1 (2017), 94–99
2.
C. S. Rjutin, “Uniform Continuity of Generalized Rational Approximations”, Math. Notes, 71:2 (2002), 236–244
3.
C. S. Rjutin, “Continuity of Operators of Generalized Rational Approximation in the Space $L_1[0;1]$”, Math. Notes, 73:1 (2003), 142–147
4.
A. R. Alimov, K. S. Ryutin, I. G. Tsar'kov, “Existence, uniqueness, and stability of best and near-best approximations”, Russian Math. Surveys, 78:3 (2023), 399–442
5.
B. S. Kashin, Yu. V. Malykhin, K. S. Ryutin, “Kolmogorov width and approximate rank”, Proc. Steklov Inst. Math., 303 (2018), 140–153
6.
K. S. Ryutin, “Recovery of sparse integer vectors from linear measurements”, Russian Math. Surveys, 74:6 (2019), 1129–1131
7.
C. S. Rjutin, “Lipshitz retractions and the operator of generalized rational approximation”, Fundam. Prikl. Mat., 6:4 (2000), 1205–1220
C. S. Rjutin, “On Uniformly Continuous Almost Best Generalized Rational Approximation Operators”, Math. Notes, 87:1 (2010), 141–145
10.
Yu. V. Malykhin, K. S. Ryutin, “Widths and rigidity of unconditional sets and random vectors”, Izv. Math., 89:2 (2025), 261–273
11.
Yu. V. Malykhin, K. S. Ryutin, “Concentration of the $L_1$-norm of trigonometric polynomials and entire functions”, Sb. Math., 205:11 (2014), 1620–1649
12.
Yuri Malykhin, Konstantin Ryutin, Tatyana Zaitseva, “Recovery of regular ridge functions on the ball”, Constr. Approx., 56 (2022), 687–708 , arXiv: 2102.13203
K. S. Ryutin, “Integer Sampling Matrices with Small Entries Ensuring Vector Recovery”, Math. Notes, 107:2 (2020), 363–366
14.
S. V. Konyagin, Yu. V. Malykhin, C. S. Rjutin, “On Exact Recovery of Sparse Vectors from Linear Measurements”, Math. Notes, 94:1 (2013), 107–114
15.
T. I. Zaitseva, Yu. V. Malykhin, K. S. Ryutin, “On Recovery of Regular Ridge Functions”, Math. Notes, 109:2 (2021), 307–311
16.
A. A. Vasil'eva, A. V. Gorshkov, M. P. Zapletin, L. V. Lokutsievskiy, G. G. Magaril-Il'yaev, K. Yu. Osipenko, K. S. Ryutin, A. V. Fursikov, “Main recent research results of the staff of the Chair of General Problems of Control”, Moscow University Mathematics Bulletin, 79:6 (2024), 351–359
17.
A. S. Rubtsova, K. S. Ryutin, V. N. Temlyakov, “On the fixed volume discrepancy of the Korobov point sets”, Sb. Math., 212:8 (2021), 1180–1192
18.
Yu. V. Malykhin, K. S. Ryutin, “On the concentration of measure and the $L^1$-norm”, J. Approx. Theory, 175 (2013), 77–82
19.
C. S. Rjutin, “A Lower Bound for Pseudodimension in Terms of Topological Dimension”, Math. Notes, 70:1 (2001), 143–144
20.
Yu. V. Malykhin, K. S. Ryutin, “Kolmogorov widths of balls in mixed norms: the case of rigidity”, Trudy Mat. Inst. Steklova, 331, 2025 (to appear)
21.
A. R. Alimov, A. A. Vasil'eva, S. V. Konyagin, A. S. Kochurov, A. I. Kozko, T. P. Lukashenko, K. S. Ryutin, V. M. Tikhomirov, A. V. Fursikov, V. N. Chubarikov, “Igor Germanovich Tsarkov (to 60th anniversary)”, Vestnik Moskov. Univ. Ser. 1. Mat. Mekh., 2020, no. 4, 70–71
22.
B. S. Kashin, Yu. V. Malykhin, V. Yu. Protasov, K. S. Ryutin, I. D. Shkredov, “Sergei Vladimirovich Konyagin turns 60”, Proc. Steklov Inst. Math., 303 (2018), 1–9
23.
S. V. Konyagin, Yu. V. Malykhin, K. S. Ryutin, “Letter to the Editor”, Math. Notes, 96:3 (2014), 462
24.
Teoriya priblizhenii, funktsionalnyi analiz i prilozheniya, Sbornik statei. K 70-letiyu akademika Borisa Sergeevicha Kashina, Trudy MIAN, 319, ed. S. V. Konyagin, M. I. Dyachenko, V. N. Temlyakov, M. R. Gabdullin, K. S. Ryutin, MIAN, M., 2022 , 328 pp.
25.
Garmonicheskii analiz, teoriya priblizhenii i teoriya chisel, Sbornik statei. K 60-letiyu so dnya rozhdeniya akademika Sergeya Vladimirovicha Konyagina, Trudy MIAN, 303, ed. B. S. Kashin, Yu. V. Malykhin, V. Yu. Protasov, I. D. Shkredov, K. S. Ryutin, MAIK «Nauka/Interperiodika», M., 2018 , 287 pp.
An extremal problem for integer sparse recovery S. V. Konyagin, K. S. Rjutin XVI International Conference «Algebra, Number Theory and Discrete Geometry: modern problems, applications and problems of history» dedicated to the 80th anniversary of the birth of Professor Michel Desa May 13, 2019 15:00
On the concentration of $L_1$ norm Yu. V. Malykhin, K. S. Ryutin International conference "Nonlinear Approximations and Applications" dedicated to the 60th birthday of Professor V. N. Temlyakov November 1, 2013 17:00
Approximation Theory, Functional Analysis, and Applications, Collected papers. On the occasion of the 70th birthday of Academician Boris Sergeevich Kashin, Trudy Mat. Inst. Steklova, 319, ed. S. V. Konyagin, M. I. Dyachenko, V. N. Temlyakov, M. R. Gabdullin, K. S. Ryutin, 2022, 328 с. http://mi.mathnet.ru/book1903
Harmonic analysis, approximation theory, and number theory, Collected papers. Dedicated to Academician Sergei Vladimirovich Konyagin on the occasion of his 60th birthday, Trudy Mat. Inst. Steklova, 303, ed. B. S. Kashin, Yu. V. Malykhin, V. Yu. Protasov, I. D. Shkredov, K. S. Ryutin, 2018, 287 с. http://mi.mathnet.ru/book1734
