Abstract
Ap-Helson set is defined to be a closed subsetE of the circle groupT with the property that every continuous function onE can be extended to the full circle in such a way that this extension has its sequence of Fourier coefficients inl p. For 1<p<2, the union of two such sets is again ap-Helson set. It is shown that thep-Helson sets (p>1) differ from the Helson sets and also that the notion really depends on the indexp. An analogue of H. Helson’s result is given: ap-Helson set supports no nonzero measure with Fourier-Stieltjes transform inl q, 1/p+1/q=1.
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References
N. K. Bary,A Treatise on Trigonometric Series, Vol. 1, Macmillan, New York, 1964.
C. C. Graham,Compact independent sets and Haar measure, Proc. Amer. Math. Soc. (to appear).
H. Helson,Fourier transforms on perfect sets, Studia Math.14 (1954), 209–213.
E. Hewitt and K. Ross,Abstract Harmonic Analysis II, Springer-Verlag, New York, 1970.
J. P. Kahane R. Salem,Ensembles Parfaits et Séries Trigonométriques, Hermann, Paris, 1963.
J. P. Kahane,Séries de Fourier absolument convergent, Ergebnisse der Mathematik, Band 50, Springer-Verlag, New York, 1970.
Y. Katznelson,An Introduction to Harmonic Analysis, Wiley, New York, 1968.
W. Rudin,Trigonometric series with gaps, J. Math. Mech.9 (1960), 203–228.
W. Rudin,Fourier Analysis on Groups, Interscience, New York, 1962.
W. Rudin,Real and Complex Analysis, McGraw-Hill, New York, 1966.
R. Salem,On sets of multiplicity for trigonometrical series, Amer. J. Math.64 (1942), 531–538.
N. Th. Varopoulos,Sur la réunion de deux ensembles de Helson,C. R. Acad. Sci. Paris. 271, 251–253.
I. Wik,On linear dependence in closed sets, Ark. Mat.4 (1960), 209–218.
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Gregory, M.B. p-Helson sets, 1<p<2. Israel J. Math. 12, 356–368 (1972). https://doi.org/10.1007/BF02764627
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DOI: https://doi.org/10.1007/BF02764627