| Title: | Universally divergent Fourier series via Landau's extremal functions (English) | 
| Author: | Herzog, Gerd | 
| Author: | Kunstmann, Peer Chr. | 
| Language: | English | 
| Journal: | Commentationes Mathematicae Universitatis Carolinae | 
| ISSN: | 0010-2628 (print) | 
| ISSN: | 1213-7243 (online) | 
| Volume: | 56 | 
| Issue: | 2 | 
| Year: | 2015 | 
| Pages: | 159-168 | 
| Summary lang: | English | 
| . | 
| Category: | math | 
| . | 
| Summary: | We prove the existence of functions $f\in A(\mathbb D)$, the Fourier series of which being universally divergent on countable subsets of $\mathbb T = \partial \mathbb D$. The proof is based on a uniform estimate of the Taylor polynomials of Landau's extremal functions on $\mathbb T\setminus\{1\}$. (English) | 
| Keyword: | Fourier series | 
| Keyword: | universal functions | 
| Keyword: | Landau's extremal functions | 
| MSC: | 30B30 | 
| MSC: | 42A16 | 
| MSC: | 47B38 | 
| idZBL: | Zbl 06433815 | 
| idMR: | MR3338730 | 
| DOI: | 10.14712/1213-7243.2015.115 | 
| . | 
| Date available: | 2015-04-25T16:59:20Z | 
| Last updated: | 2017-08-07 | 
| Stable URL: | http://hdl.handle.net/10338.dmlcz/144238 | 
| . | 
| Reference: | [1] Anderson J.M., Clunie J., Pommerenke Ch.: On Bloch functions and normal functions.J. Reine Angew. Math. 270 (1974), 12–37. Zbl 0292.30030, MR 0361090 | 
| Reference: | [2] Beise H.-P., Müller J.: On the boundary behaviour of Taylor series in Hardy and Bergman spaces.preprint, 2014. | 
| Reference: | [3] Bernal-González L.: Lineability of universal divergence of Fourier series.Integral Equations Operator Theory 74 (2012), 271–279. Zbl 1282.47008, MR 2983066, 10.1007/s00020-012-1984-6 | 
| Reference: | [4] Fejér L.: Über die Koeffizientensumme einer beschränkten und schlichten Potenzreihe.Acta Math. 49 (1926), 183–190. MR 1555240, 10.1007/BF02543853 | 
| Reference: | [5] Grosse-Erdmann K.-G.: Universal families and hypercyclic operators.Bull. Amer. Math. Soc. (N.S.) 36 (1999), 345–381. Zbl 0933.47003, MR 1685272, 10.1090/S0273-0979-99-00788-0 | 
| Reference: | [6] Grosse-Erdmann K.-G., Peris Manguillot A.: Linear Chaos.Universitext, Springer, London, 2011. Zbl 1246.47004, MR 2919812 | 
| Reference: | [7] Kahane J.-P.: Baire's category theorem and trigonometric series.J. Anal. Math. 80 (2000), 143–182. Zbl 0961.42001, MR 1771526, 10.1007/BF02791536 | 
| Reference: | [8] Katsoprinakis E., Nestoridis V., Papachristodoulos C.: Universality and Cesàro summability.Comput. Methods Funct. Theory 12 (2012), 419–448. Zbl 1262.30071, MR 3058515 | 
| Reference: | [9] Landau E., Gaier D.: Darstellung und Begründung einiger neuerer Ergebnisse der Funktionentheorie.Springer, Berlin, 1986. Zbl 0601.30001, MR 0869998 | 
| Reference: | [10] Müller J.: Continuous functions with universally divergent Fourier series on small subsets of the circle.C.R. Math. Acad. Sci. Paris 348 (2010), 1155–1158. Zbl 1204.42008, MR 2738918, 10.1016/j.crma.2010.10.026 | 
| Reference: | [11] Pogosyan N.B.: Universal Fourier series.Uspekhi Mat. Nauk 38 (1983), 185–186. Zbl 0525.42003, MR 0693740 | 
| Reference: | [12] Rudin W.: Real and Complex Analysis.McGraw-Hill Book Co., New York, 1987. Zbl 1038.00002, MR 0924157 | 
| Reference: | [13] Wintner A.: The theorem of Eneström and the extremal functions of Landau-Schur.Math. Scand. 5 (1957), 236–240. Zbl 0081.07103, MR 0098192 | 
| Reference: | [14] Zygmund A.: Trigonometric Series. Vol. I, II.Cambridge University Press, Cambridge, 2002. MR 1963498 | 
| . |