Abstract
We study the trigonometric series \(\sum_{n=1}^\infty \lambda_n \cos nx\) and \(\sum_{n=1}^\infty \lambda_n \sin nx\) with \(\{\lambda_n\}\) being a sequence of bounded variation. Let \(\psi\) denote the sum of such a series. We obtain necessary and sufficient conditions for the validity of the weighted Fourier inequality \(\left(\intop_0^\pi\mathopen|\psi(x)|^q \omega(x)\,dx\right)^{1/q} \le C\!\left(\sum_{n=1}^\infty u_n\left(\sum_{k=n}^\infty\mathopen|\lambda_{k}-\lambda_{k+1}|\right)^p \right)^{1/p}\), \(0<p\le q<\infty\), in terms of the weight \(\omega\) and the weighted sequence \(\{u_n\}\). Applications to the series with general monotone coefficients are given.
Similar content being viewed by others
References
K. F. Andersen, “On the transformation of Fourier coefficients of certain classes of functions. II,” Pac. J. Math. 105 (1), 1–10 (1983).
K. F. Andersen and H. P. Heinig, “Weighted norm inequalities for certain integral operators,” SIAM J. Math. Anal. 14 (4), 834–844 (1983).
K. F. Andersen and B. Muckenhoupt, “Weighted weak type Hardy inequalities with applications to Hilbert transforms and maximal functions,” Stud. Math. 72, 9–26 (1981).
M. Ariño and B. Muckenhoupt, “Maximal functions on classical Lorentz spaces and Hardy’s inequality with weights for nonincreasing functions,” Trans. Am. Math. Soc. 320 (2), 727–735 (1990).
R. Askey, “Norm inequalities for some orthogonal series,” Bull. Am. Math. Soc. 72, 808–823 (1966).
R. Askey, “A transplantation theorem for Jacobi coefficients,” Pac. J. Math. 21, 393–404 (1967).
R. Askey and S. Wainger, “Integrability theorems for Fourier series,” Duke Math. J. 33, 223–228 (1966).
R. Askey and S. Wainger, “A transplantation theorem for ultraspherical coefficients,” Pac. J. Math. 16, 393–405 (1966).
N. K. Bari, Trigonometric Series (Fizmatgiz, Moscow, 1961). Engl. transl.: N. K. Bary, A Treatise on Trigonometric Series (Pergamon Press, Oxford, 1964), Vols. I, II.
N. K. Bari and S. B. Stechkin, “Best approximations and differential properties of two conjugate functions,” Tr. Mosk. Mat. Obshch. 5, 483–522 (1956).
J. J. Benedetto and H. P. Heinig, “Weighted Fourier inequalities: New proofs and generalizations,” J. Fourier Anal. Appl. 9 (1), 1–37 (2003).
G. Bennett and K.-G. Grosse-Erdmann, “Weighted Hardy inequalities for decreasing sequences and functions,” Math. Ann. 334 (3), 489–531 (2006).
R. P. Boas Jr., Integrability Theorems for Trigonometric Transforms (Springer, Berlin, 1967).
C. Carton-Lebrun and H. P. Heinig, “Weighted Fourier transform inequalities for radially decreasing functions,” SIAM J. Math. Anal. 23 (3), 785–798 (1992).
L. De Carli, D. Gorbachev, and S. Tikhonov, “Pitt inequalities and restriction theorems for the Fourier transform,” Rev. Mat. Iberoam. 33 (3), 789–808 (2017).
A. Debernardi, “Weighted norm inequalities for generalized Fourier-type transforms and applications,” Publ. Mat. 64 (1), 3–42 (2020).
A. Debernardi, “The Boas problem on Hankel transforms,” J. Fourier Anal. Appl 25 (6), 3310–3341 (2019).
Ó. Domínguez, D. D. Haroske, and S. Tikhonov, “Embeddings and characterizations of Lipschitz spaces,” J. Math. Pures Appl. 144, 69–105 (2020); arXiv: 1911.08369 [math.FA].
Ó. Domínguez and S. Tikhonov, “Function spaces of logarithmic smoothness: Embeddings and characterizations,” Mem. Am. Math. Soc. (in press); arXiv: 1811.06399 [math.FA].
Ó. Domínguez and M. Veraar, “Extensions of the vector-valued Hausdorff–Young inequalities,” arXiv: 1904.07930 [math.FA].
M. Dyachenko, A. Mukanov, and S. Tikhonov, “Hardy–Littlewood theorems for trigonometric series with general monotone coefficients,” Stud. Math. 250 (3), 217–234 (2020).
M. Dyachenko, E. Nursultanov, and A. Kankenova, “On summability of Fourier coefficients of functions from Lebesgue space,” J. Math. Anal. Appl. 419 (2), 959–971 (2014).
M. Dyachenko and S. Tikhonov, “Convergence of trigonometric series with general monotone coefficients,” C. R., Math., Acad. Sci. Paris 345 (3), 123–126 (2007).
M. Dyachenko and S. Tikhonov, “Integrability and continuity of functions represented by trigonometric series: Coefficients criteria,” Stud. Math. 193 (3), 285–306 (2009).
A. Gogatishvili and V. D. Stepanov, “Reduction theorems for weighted integral inequalities on the cone of monotone functions,” Russ. Math. Surv. 68 (4), 597–664 (2013) [transl. from Usp. Mat. Nauk 68 (4), 3–68 (2013)].
M. L. Gol’dman, “Estimates of norms of Hardy-type integral and discrete operators on cones of quasimonotone functions,” Dokl. Math. 63 (2), 250–255 (2001) [transl. from Dokl. Akad. Nauk 377 (6), 733–738 (2001)].
M. L. Goldman, “Sharp estimates for the norms of Hardy-type operators on the cones of quasimonotone functions,” Proc. Steklov Inst. Math. 232, 109–137 (2001) [transl. from Tr. Mat. Inst. Steklova 232, 115–143 (2001)].
B. I. Golubov, A. V. Efimov, and V. A. Skvortsov, Walsh Series and Transforms: Theory and Applications (Nauka, Moscow, 1987; Kluwer, Dordrecht, 1991).
D. Gorbachev, E. Liflyand, and S. Tikhonov, “Weighted norm inequalities for integral transforms,” Indiana Univ. Math. J. 67 (5), 1949–2003 (2018).
D. Gorbachev and S. Tikhonov, “Moduli of smoothness and growth properties of Fourier transforms: Two-sided estimates,” J. Approx. Theory 164 (9), 1283–1312 (2012).
G. H. Hardy and J. E. Littlewood, “Notes on the theory of series. XIII: Some new properties of Fourier constants,” J. London Math. Soc. 6, 3–9 (1931).
H. Heinig, “Weighted norm inequalities for classes of operators,” Indiana Univ. Math. J. 33 (4), 573–582 (1984).
W. Jurkat and G. Sampson, “On rearrangement and weight inequalities for the Fourier transform,” Indiana Univ. Math. J. 33 (2), 257–270 (1984).
C. N. Kellogg, “An extension of the Hausdorff–Young theorem,” Mich. Math. J. 18, 121–127 (1971).
A. A. Konyushkov, “Best approximations by trigonometric polynomials and Fourier coefficients,” Mat. Sb. 44 (1), 53–84 (1958).
A. Kufner and L.-E. Persson, Weighted Inequalities of Hardy Type (World Scientific, Singapore, 2003).
E. Liflyand and S. Tikhonov, “A concept of general monotonicity and applications,” Math. Nachr. 284 (8–9), 1083–1098 (2011).
E. Liflyand and S. Tikhonov, “Two-sided weighted Fourier inequalities,” Ann. Sc. Norm. Super. Pisa, Cl. Sci., Ser. 5, 11 (2), 341–362 (2012).
B. Muckenhoupt, “Hardy’s inequality with weights,” Stud. Math. 44, 31–38 (1972).
E. D. Nursultanov, “On the coefficients of multiple Fourier series in \(L_p\)-spaces,” Izv. Math. 64 (1), 93–120 (2000) [transl. from Izv. Ross. Akad. Nauk, Ser. Mat. 64 (1), 95–122 (2000)].
E. Nursultanov and S. Tikhonov, “Weighted Fourier inequalities in Lebesgue and Lorentz spaces,” J. Fourier Anal. Appl. 26 (4), 57 (2020).
H. R. Pitt, “Theorems on Fourier series and power series,” Duke Math. J. 3 (4), 747–755 (1937).
J. Rastegari and G. Sinnamon, “Weighted Fourier inequalities via rearrangements,” J. Fourier Anal. Appl. 24 (5), 1225–1248 (2018).
Y. Sagher, “An application of interpolation theory to Fourier series,” Stud. Math. 41, 169–181 (1972).
E. M. Stein, “Interpolation of linear operators,” Trans. Am. Math. Soc. 83, 482–492 (1956).
S. Yu. Tikhonov, “On the integrability of trigonometric series,” Math. Notes 78 (3–4), 437–442 (2005) [transl. from Mat. Zametki 78 (3), 476–480 (2005)].
S. Tikhonov, “Trigonometric series with general monotone coefficients,” J. Math. Anal. Appl. 326 (1), 721–735 (2007).
S. Tikhonov, “Best approximation and moduli of smoothness: Computation and equivalence theorems,” J. Approx. Theory 153 (1), 19–39 (2008).
P. L. Ul’yanov, “Application of \(A\)-integration to a class of trigonometric series,” Mat. Sb. 35 (3), 469–490 (1954).
W. H. Young, “On the Fourier series of bounded functions,” Proc. London Math. Soc. 12, 41–70 (1913).
D. Yu, P. Zhou, and S. Zhou, “On \(L^p\) integrability and convergence of trigonometric series,” Stud. Math. 182 (3), 215–226 (2007).
A. Zygmund, Trigonometric Series (Cambridge Univ. Press, Cambridge, 2002).
Acknowledgments
I would like to thank A. Gogatishvili, M. L. Goldman, and V. D. Stepanov for their comments on Hardy’s inequality. I am also grateful to Amiran Gogatishvili for his remarks regarding Proposition 2.2.
Funding
This research was partially supported by Ministerio de Ciencia, Innovación y Universidades (grant MTM 2017-87409-P) and Generalitat de Catalunya (grant 2017 SGR 358).
Author information
Authors and Affiliations
Corresponding author
Additional information
Published in Russian in Trudy Matematicheskogo Instituta imeni V.A. Steklova, 2021, Vol. 312, pp. 294–312 https://doi.org/10.4213/tm4130.
Rights and permissions
About this article
Cite this article
Tikhonov, S.Y. Weighted Fourier Inequalities and Boundedness of Variation. Proc. Steklov Inst. Math. 312, 282–300 (2021). https://doi.org/10.1134/S0081543821010193
Received:
Revised:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1134/S0081543821010193