Hereditary Hsu-Robbins-Erdös Law of Large Numbers

Fuente: arXiv
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Auteurs principaux: Berkes, Istvan, Karatzas, Ioannis, Schachermayer, Walter
Format: Preprint
Publié: 2025
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author Berkes, Istvan
Karatzas, Ioannis
Schachermayer, Walter
author_facet Berkes, Istvan
Karatzas, Ioannis
Schachermayer, Walter
contents We show that every sequence $f_1, f_2, \cdots$ of real-valued random variables with $\sup_{n \in \N} \E (f_n^2) < \infty$ contains a subsequence $f_{k_1}, f_{k_2}, \cdots$ converging in \textsc{Cesàro} mean to some $\,f_\infty \in \mathbb{L}^2$ {\it completely,} to wit, $ \sum_{N \in \N} \, ¶\left( \bigg| \frac{1}{N} \sum_{n=1}^N f_{k_n} - f_\infty \bigg| > \eps \right)< \infty\,, \quad \forall ~ \eps > 0\,; $ and {\it hereditarily,} i.e., along all further subsequences as well. We also identify a condition, slightly weaker than boundedness in $ \mathbb{L}^2,$ which turns out to be not only sufficient for the above hereditary complete convergence in \textsc{Cesàro} mean, but necessary as well.
format Preprint
id arxiv_https___arxiv_org_abs_2503_19484
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Hereditary Hsu-Robbins-Erdös Law of Large Numbers
Berkes, Istvan
Karatzas, Ioannis
Schachermayer, Walter
Probability
Primary 60A10, 60F15, Secondary 60G42, 60G46
G.3
We show that every sequence $f_1, f_2, \cdots$ of real-valued random variables with $\sup_{n \in \N} \E (f_n^2) < \infty$ contains a subsequence $f_{k_1}, f_{k_2}, \cdots$ converging in \textsc{Cesàro} mean to some $\,f_\infty \in \mathbb{L}^2$ {\it completely,} to wit, $ \sum_{N \in \N} \, ¶\left( \bigg| \frac{1}{N} \sum_{n=1}^N f_{k_n} - f_\infty \bigg| > \eps \right)< \infty\,, \quad \forall ~ \eps > 0\,; $ and {\it hereditarily,} i.e., along all further subsequences as well. We also identify a condition, slightly weaker than boundedness in $ \mathbb{L}^2,$ which turns out to be not only sufficient for the above hereditary complete convergence in \textsc{Cesàro} mean, but necessary as well.
title Hereditary Hsu-Robbins-Erdös Law of Large Numbers
topic Probability
Primary 60A10, 60F15, Secondary 60G42, 60G46
G.3
url https://arxiv.org/abs/2503.19484