A survey on recent notions of singularity for kernels of nonlinear integral operators

Authors

DOI:

https://doi.org/10.64700/mmm.90

Keywords:

Singularity, generalized Lipschitz conditions, nonlinear integral operators, locally compact topological spaces, modular spaces

Abstract

In this paper, we review several notions of singularity for kernels of abstract nonlinear integral operators acting on functions defined over locally compact Hausdorff topological spaces or groups. A recent general definition of abstract nonlinear operators is also discussed, which includes some discrete operators, as the sampling series in a nonlinear form.

References

[1] L. Angeloni, G. Vinti: A unified approach to approximation results with applications to nonlinear sampling theory, Int. Journal Math. Sci., 3 (1) (2004), 93–128.

[2] L. Angeloni, G. Vinti: Rate of approximation for nonlinear integral operators with application to signal processing, Differential Integral Equations, 18 (8) (2005), 855–890.

[3] L. Angeloni, G. Vinti: Convergence in variation and rate of approximation for nonlinear integral operators of convolution type, Results Math., 49 (1-2) (2006), 1–23.

[4] L. Angeloni, F. Vici: Approximation methods in BV for nonlinear generalized sampling series, Results Math., 80 (4) (2025), Article ID:99.

[5] C. Bardaro, A. Boccuto, X. Dimitriou and I. Mantellini: Modular filter convergence theorems for abstract sampling type operators, 92 (11) (2013), 1404–2423.

[6] C. Bardaro, P. L. Butzer, I. Mantellini and G. Schmeisser: Mellin Analysis, Transform Theory, and Applications, Birkhauser, (2025).

[7] C. Bardaro, H. Karsli and G. Vinti: Nonlinear integral operators with homogeneous kernels: pointwise approximation theorems, Appl.Anal., 90 (3-4) (2011), 463–474.

[8] C. Bardaro, I. Mantellini: A modular convergence theorem for nonlinear integral operators, Commentationes Math., 36 (1996), 27–37.

[9] C. Bardaro, I. Mantellini: Modular approximation by sequences of nonlinear integral operators in Musielak–Orlicz spaces, Atti Sem. Mat. Fis. Univ. Modena, 46 (1998), 403–425.

[10] C. Bardaro, I. Mantellini: On a singularity concept for kernels of nonlinear integral operators, Intern. Math. Journal, 1 (3) (2002), 239–254.

[11] C. Bardaro, I. Mantellini: On approximation properties of Urysohn integral operators, Intern. Journal of Pure and Appl. Math., 3 (2002), 129–148.

[12] C. Bardaro, I. Mantellini: Uniform modular integrability and convergence properties for a class of Urysohn integral operators in function spaces, Math. Slovaca, 56 (4) (2006), 465–482.

[13] C. Bardaro, I. Mantellini: On global approximation properties of abstract integral operators in Orlicz spaces and applications, J. Inequalities in Pure and Applied Math., 6 (4) (2005), Article ID:123.

[14] C. Bardaro, I. Mantellini: Approximation properties in abstract modular spaces for a class of general sampling-type operators, Appl. Anal., 85 (4) (2006), 383–413.

[15] C. Bardaro, I. Mantellini: Estimates of the approximation error for abstract sampling type operators in Orlicz spaces, Funct. Approx. Comment. Math., 26 (2006), 45–70.

[16] C. Bardaro, J. Musielak and G. Vinti: Approximation by nonlinear integral operators in some modular function spaces, Annales Polonici Math., 63 (1996), 173–182.

[17] C. Bardaro, J. Musielak and G. Vinti: Nonlinear operators of integral type in some functional spaces, Collect. Math., 48 (1997), 409–422.

[18] C. Bardaro, J. Musielak and G. Vinti: On nonlinear integro-differential operators in generalized Orlicz-Sobolev spaces, J. Approx. Theory, 105 (2000), 238–251.

[19] C. Bardaro, J. Musielak and G. Vinti: Nonlinear integral operators and applications, 9, De Gruyter, Berlin-New York (2003).

[20] C. Bardaro, S. Sciamannini and G. Vinti: Convergence in BVϕ by nonlinear Mellin-type convolution operators, Funct. Approx. Comment. Math., 29 (2001), 17–28.

[21] C. Bardaro, G. Vinti: A modular convergence theorem for certain nonlinear integral operators with homogeneous kernel, Collect. Math., 48 (1997), 393–407.

[22] C. Bardaro, G. Vinti: Uniform convergence and rate of approximation for a nonlinear version of the generalized sampling operators, Result. Math., 34 (1998), 224–240.

[23] C. Bardaro, G. Vinti: An abstract approach to sampling type operators inspired by the work of P.L. ButzerPart II- Nonlinear operators, Sampl. Theory Signal Image Process., 3 (1) (2004), 29–44.

[24] P. L. Butzer, S. Jansche: A direct approach to Mellin transform, J. Fourier Anal. Appl., 3 (4) (1997), 325–376.

[25] P. L. Butzer, S. Jansche: Mellin transform, the Mellin-Poisson summation formula and the exponential sampling theorem, Atti Sem. Mat. Fis. Univ. Modena, 46, (1998), 99–122.

[26] P. L. Butzer, S. Jansche: The finite Mellin Transform, Mellin–Fourier series and the Mellin–Poisson summation formula, Rend. Circ. Mat. Palermo, Ser. II, 52 (1998), 55–81.

[27] P. L. Butzer, S. Jansche: A self-contained approach to Mellin transform analysis for square integrable functions, applications, Integral Transforms Spec. Funct., 8 (1999), 175–198.

[28] P. L. Butzer, S. Jansche: Mellin–Fourier series and the classical Mellin transform, Comput. Math. Appl., 40 (1) (2000), 49–62.

[29] P. L. Butzer, R. J. Nessel: Fourier analysis and approximation I, Academic Press, New York-London (1971).

[30] P. L. Butzer, R. L. Stens: Sampling theory for not necessarily band-limited functions: an historical overview, SIAM Review, 34 (1992), 40–53.

[31] P. L. Butzer, R. L. Stens: Linear prediction by samples from the past, Shannon Sampling and Interpolation Theory II, Springer-Verlag, New York (1993), 157–183.

[32] D. Costarelli, M. Natale and G. Vinti: Convergence results for nonlinear sampling Kantorovich operators in modular spaces, Numer. Funct. anal. Optim., 44 (12) (2023), 1276–1299.

[33] K. Demirci: I-limit superior and limit inferior, Math. Comm., 6 (2001), 165–172.

[34] H. Fast: Sur la convergence statistique, Colloq. Math., 2 (1951), 241–244.

[35] G. B. Folland: Real analysis: modern techniques and their applications, Wiley and Sons, New York (1984).

[36] E. Hewitt, K. A. Ross: Abstract harmonic analysis vol. II: Structure and analysis for compact groups, analysis on locally compact Abelian groups, Springer, New York (1970).

[37] J. R. Higgins: Sampling Theory in Fourier and Signal Analysis: Foundations, Oxford Univ. Press, Oxford, (1996).

[38] W. M. Kozlowski: Modular Function Spaces, Pure Appl. Math., Marcel Dekker, New York and Basel (1988).

[39] I. Mantellini, G. Vinti: Approximation results for nonlinear integral operators in modular spaces and applications, Annales Polonici Math., 46 (1) (2003), 55–71.

[40] J. Musielak: On some approximation problems in modular spaces, Proc. Int. Conf. Constructive Function Theory, Varna (1981), Sofia (1983), 455–461.

[41] J. Musielak: Orlicz spaces and modular spaces, Lecture Notes in Math., Springer-Verlag, Berlin (1983).

[42] J. Musielak: Nonlinear approximation in some modular function spaces I, Math. Japonica, 38 (1993), 83–90.

[43] H. Steinhaus: Sur la convergence ordinaire et la convergence asymptotique, Colloq. Math., 2 (1951), 73–74.

[44] G. Vinti: A general approximation result for nonlinear integral operators and applications to signal processing, Appl. Anal., 79 (2001), 21—238.

[45] G. Vinti, L. Zampogni: Approximation by means of nonlinear Kantorovich sampling type operators in Orlicz spaces, J. Approx. Theory, 161 (2) (2009), 511–528.

[46] G. Vinti, L. Zampogni: A general method to study the convergence of nonlinear operators in Orlicz spaces, Adv. Nonlinear Studies, 22 (1) (2022), 594–618.

[47] S. Willard: General topology, Addison Wesley Publ. Comp., Massachusetts (1968).

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Published

15-04-2026

How to Cite

Mantellini, I., & Bardaro, C. (2026). A survey on recent notions of singularity for kernels of nonlinear integral operators. Modern Mathematical Methods, 4(1), 14–29. https://doi.org/10.64700/mmm.90

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