Abstract
It is known that the maximal operator \({\sigma^{\kappa,*}(f)} := sup_{n \in \mathbf{P}}{|{\sigma}_{n}^{\kappa} (f)|}\) is bounded from the dyadic Hardy space \({H_{p}}\) into the space \({L_{p}}\) for \({p > 2/3}\) [6]. Moreover, Goginava and Nagy showed that \({\sigma^{\kappa,*}}\) is not bounded from the Hardy space \({H_{2/3}}\) to the space \({L_{2/3}}\) [9]. The main aim of this paper is to investigate the case \({0 < p < 2/3}\). We show that the weighted maximal operator \({\tilde{\sigma}^{\kappa,*,p}(f) :=sup_{n\in \mathbf{P}} \frac{|{\sigma}_{n}^\kappa (f)|}{n^{2/p-3}}}\), is bounded from the Hardy space \({H_{p}}\) into the space \({L_{p}}\) for any \({0 < p < 2/3}\). With its aid we provide a necessary and sufficient condition for the convergence of Walsh–Kaczmarz–Marcinkiewicz means in terms of modulus of continuity on the Hardy space \({H_p}\), and prove a strong convergence theorem for this means.
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Research is supported by project TÁMOP-4.2.2.A-11/1/KONV-2012-0051, Campus Hungary grant B2/4R/15701 and Shota Rustaveli National Science Foundation grants YS15-2.1.1-47 and DI/9/5-100/13.
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Nagy, K., Tephnadze, G. The Walsh–Kaczmarz–Marcinkiewicz means and Hardy spaces. Acta Math. Hungar. 149, 346–374 (2016). https://doi.org/10.1007/s10474-016-0617-y
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DOI: https://doi.org/10.1007/s10474-016-0617-y
Key words and phrases
- Walsh–Kaczmarz system
- Marcinkiewicz means
- maximal operator
- two-dimensional system
- strong convergence
- modulus of continuity