English

Some remarks on Davis inequality for biparameter filtrations

Probability 2025-09-30 v1

Abstract

The Davis inequality ESfEf\mathbb{E} Sf\simeq \mathbb{E} f^* between L1L^1 norms of square function of a martingale and its maximal function is known for martingales indexed by linearly ordered filtrations and in some particular cases for double indexed one. We prove the \gtrsim inequality for arbitrary filtrations satisfying the (F4) condition of Cairoli and Walsh and propose a method to attack the other inequality. The former is done by means of a two-parameter analogue of Davis-Garsia decomposition.

Cite

@article{arxiv.2509.23351,
  title  = {Some remarks on Davis inequality for biparameter filtrations},
  author = {Maciej Rzeszut},
  journal= {arXiv preprint arXiv:2509.23351},
  year   = {2025}
}
R2 v1 2026-07-01T06:00:59.199Z