Abstract
We establish a direct and a matching two-term converse estimate by a K-functional and a modulus of smoothness for the rate of approximation by generalized Kantorovich sampling operators in variable exponent Lebesgue spaces. They yield the saturation property and class of these operators. We also prove a Voronovskaya-type estimate.
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Acar, T., Costarelli, D., Vinti, G.: Linear prediction and simultaneous approximation by \(m\)-th order Kantorovich type sampling series. Banach J. Math. Anal. 14, 1481–1508 (2020)
Acar, T., Draganov, B.R.: A characterization of the rate of the simultaneous approximation by generalized sampling operators and their Kantorovich modification. J. Math. Anal. Appl. 530(2), 127740 (2024)
Akgün, R.: Trigonometric approximation of functions in generalized Lebesgue spaces with variable exponent. Ukrain. Math. J. 63(1), 3–23 (2011)
Akgün, R.: Polynomial approximation of functions in weighted Lebesgue and Smirnov spaces with nonstandard growth. Georg. Math. J. 18(2), 203–235 (2011)
Angeloni, L., Çetin, N., Costarelli, D., Sambucini, A.R., Vinti, G.: Multivariate sampling Kantorovich operators: quantitative estimates in Orlicz spaces. Constr. Math. Anal. 4(2), 229–241 (2021)
Bardaro, C., Butzer, P.L., Stens, R.L., Vinti, G.: Kantorovich-type generalized sampling series in the setting of Orlicz spaces. Sample Theory Signal Image Process. 6(1), 29–52 (2007)
Bardaro, C., Mantellini, I.: Voronovskaya formulae for Kantorovich type generalized sampling series. Int. J. Pure Appl. Math. 62(3), 247–262 (2010)
Bartoccini, B., Costarelli, D., Vinti, G.: Extension of saturation theorems for the sampling Kantorovich operators. Complex Anal. Oper. Theory 13, 1161–1175 (2019)
Butzer, P.L., Nessel, R.J.: Fourier Analysis and Approximation. Birkhäser, Basel (1971)
Butzer, P.L., Stens, R.L.: Linear prediction by samples from the past. In: Marks, R.J., II. (ed.) Advanced Topics in Shannon Sampling and Interpolation Theory, pp. 157–183. Springer, New York (1993)
Costarelli, D., Vinti, G.: Approximation by multivariate generalized sampling Kantorovich operators in the setting of Orlicz spaces. Boll. Unione Mat. Ital. Serie (9) 4(3), 445–468 (2011)
Costarelli, D., Vinti, G.: An inverse result of approximation by sampling Kantorovich series. Proc. Edinb. Math. Soc. (2) 62(1), 265–280 (2019)
Costarelli, D., Vinti, G.: Inverse results of approximation and the saturation order for the sampling Kantorovich series. J. Approx. Theory 242, 64–82 (2019)
Costarelli, D., Vinti, G.: Saturation by the Fourier transform method for the sampling Kantorovich series based on bandlimited kernels. Anal. Math. Phys. 9, 2263–2280 (2019)
Costarelli, D., Vinti, G.: Approximation results by multivariate sampling Kantorovich series in Musielak–Orlicz spaces. Dolomites Res. Notes Approx. 12, 7–16 (2019)
Costarelli, D., Vinti, G.: Approximation properties of the sampling Kantorovich operators: regularization, saturation, inverse results and Favard classes in \(L^p\)-Spaces. J. Fourier Anal. Appl. 28, 49 (2022)
Costarelli, D., Vinti, G.: Convergence of sampling Kantorovich operators in modular spaces with applications. Rend. Circ. Mat. Palermo 2(70), 1115–1136 (2021)
Costarelli, D., Vinti, G.: A quantitative estimate for the sampling Kantorovich series in terms of the modulus of continuity in Orlicz spaces. Constr. Math. Anal. 2(1), 8–14 (2019)
Cruz-Uribe, D.: Variable Lebesgue Spaces: Foundations and Harmonic Analysis. CRM Preprints, Barcelona (2012)
Cruz-Uribe, D., Diening, L., Fiorenza, A.: A new proof of the boundedness of maximal operators on variable Lebesgue spaces. Boll. Unione Mat. Ital. (9) 2(1), 151–173 (2009)
Cruz-Uribe, D., Fiorenza, A., Neugebauer, C.J.: The maximal function on variable \(L^p\) spaces. Ann. Acad. Sci. Fenn. Math. 28(1), 223–238 (2003)
Cruz-Uribe, D., Fiorenza, A., Neugebauer, C.J.: Corrections to: “The maximal function on variable \(L^p\) spaces” [Ann. Acad. Sci. Fenn. Math. 28(1), 223–238 (2003)]. Ann. Acad. Sci. Fenn. Math. 29(1), 247–249 (2004)
DeVore, R.A., Lorentz, G.G.: Constructive Approximation. Springer, Berlin (1993)
Ditzian, Z., Ivanov, K.G.: Strong converse inequalities. J. Anal. Math. 61, 61–111 (1993)
Donnini, C., Vinti, G.: Approximation by means of Kantorovich generalized sampling operators in Musielak–Orlicz spaces. PanAmerican Math. J. 18(2), 1–18 (2008)
Guven, A., Israfilov, D.M.: Trigonometric approximation in generalized Lebesgue spaces \(L^{p(x)}\). J. Math. Inequal. 4(2), 285–299 (2010)
Israfilov, D., Kokilashvili, V., Samko, S.: Approximation in weighted Lebesgue and Smirnov spaces with variable exponents. Proc. A. Razmadze Math. Inst. 143, 25–35 (2007)
Israfilov, D.M., Testici, A.: Approximation problems in the Lebesgue spaces with variable exponent. J. Math. Anal. Appl. 459(1), 112–123 (2018)
Jia, R.-Q.: Approximation with scaled shift-invariant spaces by means of quasi-projection operators. J. Approx. Theory 131(1), 30–46 (2004)
Kolomoitsev, Yu., Skopina, M.: Approximation by multivariate Kantorovich–Kotelnikov operators. J. Math. Anal. Appl. 456(1), 195–213 (2017)
Kolomoitsev, Yu., Skopina, M.: Approximation by sampling-type operators in \(L_{p}\)-spaces. Math. Meth. Appl. Sci. 43(16), 9358–9374 (2020)
Kolomoitsev, Yu., Skopina, M.: Approximation by multivariate quasi-projection operators and Fourier multipliers. Appl. Math. Comput. 400, 125955 (2021)
Kolomoitsev, Yu., Skopina, M.: Uniform approximation by multivariate quasi-projection operators. Anal. Math. Phys. 12, 68 (2022)
Nekvinda, A.: Hardy-Littlewood maximal operator on \(L^{p(x)}(^n)\). Math. Inequal. Appl. 7(2), 255–265 (2004)
Ries, S., Stens, R.L.: Approximation by generalized sampling series. In: Sendov, B., Petrushev, P., Maleev, R., Tashev, S. (eds.) Proc. Internat. Conf. “Constructive Theory of Functions”, Varna, Bulgaria, June 1984, pp. 746–756. Bulgarian Acad. Sci., Sofia (1984)
Samko, S.: Convolution type operators in \(L^{p(x)}\). Integr. Transforms Spec. Funct. 7(1–2), 123–144 (1998)
Samko, S.: Differentiation and integration of variable order and the spaces \(L^{p(x)}\). In: “Operator theory for complex and hypercomplex analysis’’ (Mexico City, 1994), Contemp. Math, vol. 212, pp. 203–219. American Mathematical Society, Providence (1998)
Sharapudinov, I.I.: Some aspects of approximation theory in the spaces \(L^{p(x)}\). Anal. Math. 33(2), 135–153 (2007)
Sharapudinov, I.I.: Approximation of functions in \(L^{p(x)}_{2\pi }\) by trigonometric polynomials. Izv. RAN Ser. Mat. 77(2), 197–224 (2013) (in Russian); English transl. Izv. Math. 77(2), 407–434 (2013)
Funding
This study is financed by the European Union-NextGenerationEU, through the National Recovery and Resilience Plan of the Republic of Bulgaria, project No BG-RRP-2.004-0008.
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Draganov, B.R. A characterization of the rate of approximation of Kantorovich sampling operators in variable exponent Lebesgue spaces. Rev. Real Acad. Cienc. Exactas Fis. Nat. Ser. A-Mat. 118, 71 (2024). https://doi.org/10.1007/s13398-024-01571-6
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DOI: https://doi.org/10.1007/s13398-024-01571-6
Keywords
- Sampling operator
- Kantorovich sampling operator
- Direct estimate
- Converse estimate
- Modulus of smoothness
- Variable exponent Lebesgue space