Abstract
We establish inequalities of Ulyanov-type for moduli of smoothness relating the source Lorentz–Zygmund space \(\, L^{p,r}(\log L)^{\alpha -\gamma },\, \gamma >0,\) and the target space \(\, L^{p^*,s}(\log L)^\alpha \) over \(\, {\mathbb R}^n\) if \(\, 1<p<p^*<\infty \) and over \(\, \mathbb {T}^n\) if \(\, 1<p \le p^*<\infty .\) The stronger logarithmic integrability (corresponding to \(\, L^{p^*,s}(\log L)^\alpha \)) is balanced by an additional logarithmic smoothness.
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Acknowledgments
The authors thank the referees for useful comments and suggestions that led to the improvement of the paper. Part of this work was done while the authors were at the Centre de Recerca Matemàtica (Barcelona) in 2011. This research was partially supported by the MTM 2011-27637, 2014 SGR 289, RFFI 13-01-00043, RVO: 67985840, the Grant Agency of the Czech Republic, Grants Nos. 201/08/0383, and P 201 13-14743S. The research of A. Gogatishvili was partially supported by the research grant no. 31/48 of the Shota Rustaveli National Science Foundation.
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Communicated by Hans G. Feichtinger.
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Gogatishvili, A., Opic, B., Tikhonov, S. et al. Ulyanov-type Inequalities Between Lorentz–Zygmund Spaces . J Fourier Anal Appl 20, 1020–1049 (2014). https://doi.org/10.1007/s00041-014-9343-4
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DOI: https://doi.org/10.1007/s00041-014-9343-4