Abstract
We consider the following question: are there exponents \(2<p<q\) such that the Riesz projection is bounded from \(L^q\) to \(L^p\) on the infinite polytorus? We are unable to answer the question, but our counter-example improves a result of Marzo and Seip by demonstrating that the Riesz projection is unbounded from \(L^\infty \) to \(L^p\) if \(p\ge 3.31138\). A similar result can be extracted for any \(q>2\). Our approach is based on duality arguments and a detailed study of linear functions. Some related results are also presented.
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Acknowledgements
The author would like to extend his gratitude to A. Bondarenko, H. Hedenmalm, E. Saksman and K. Seip for an interesting discussion which culminated in the material presented in Sect. 3 and to the referee for a helpful suggestion.
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Brevig, O.F. Linear functions and duality on the infinite polytorus. Collect. Math. 70, 493–500 (2019). https://doi.org/10.1007/s13348-019-00243-8
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DOI: https://doi.org/10.1007/s13348-019-00243-8