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On properties of weighted Hardy constant for means

Classical Analysis and ODEs 2022-11-23 v2

Abstract

For a given weighted mean M\mathscr{M} defined on a subinterval of R+\mathbb{R}_+ and a sequence of weights λ=(λn)n=1\lambda=(\lambda_n)_{n=1}^\infty we define a Hardy constant H(λ)\mathscr H(\lambda) as the smallest extended real number such that n=1λnM((x1,,xn),(λ1,,λn))H(λ)n=1λnxn for all x1(λ). \sum_{n=1}^\infty \lambda_n \mathscr{M}\big((x_1,\dots,x_n),(\lambda_1,\dots,\lambda_n)\big) \le \mathscr H(\lambda) \cdot \sum_{n=1}^\infty \lambda_n x_n \text{ for all }x \in \ell^1(\lambda). The aim of this note is to present a comprehensive study of the mapping H\mathscr H. For example we prove that it is lower semicontinuous in the pointwise topology. Moreover we show that whenever M\mathscr{M} is a monotone and Jensen-concave mean which is continuous in its weights then H\mathscr H is monotone with respect to the partitioning of the vector. Finally we deliver some sufficient conditions for λ\lambda to validate the equality H(λ)=supH\mathscr H(\lambda)=\sup \mathscr H for every symmetric and monotone mean.

Keywords

Cite

@article{arxiv.2003.06025,
  title  = {On properties of weighted Hardy constant for means},
  author = {Paweł Pasteczka},
  journal= {arXiv preprint arXiv:2003.06025},
  year   = {2022}
}

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