Abstract:
The paper concerns with necessary and sufficient conditions providing that a function of many variables with nonnegative trigonometric Fourier coefficients velongs to the big and small Zygmund classes. Earler, such a result was obtained by R. P. Boas in the
one-dimensional case and by V. Fulop in the two-dimensional case.
Key words:functions of many variables, Fourier coefficients, Zygmund classes.
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