English

Intersecting sets in probability spaces and Shelah's classification

Combinatorics 2024-06-28 v1 Logic Probability

Abstract

For nNn \in \mathbb{N} and ε>0\varepsilon > 0, given a sufficiently long sequence of events in a probability space all of measure at least ε\varepsilon, some nn of them will have a common intersection. A more subtle pattern: for any 0<p<q<10 < p < q < 1, we cannot find events AiA_i and BiB_i so that μ(AiBj)p\mu \left( A_i \cap B_j \right) \leq p and μ(AjBi)q\mu \left( A_j \cap B_i\right) \geq q for all 1<i<j<n1 < i < j < n, assuming nn is sufficiently large. This is closely connected to model-theoretic stability of probability algebras. We survey some results from our recent work on more complicated patterns that arise when our events are indexed by multiple indices. In particular, how such results are connected to higher arity generalizations of de Finetti's theorem in probability, structural Ramsey theory, hypergraph regularity in combinatorics, and model theory.

Keywords

Cite

@article{arxiv.2406.18772,
  title  = {Intersecting sets in probability spaces and Shelah's classification},
  author = {Artem Chernikov and Henry Towsner},
  journal= {arXiv preprint arXiv:2406.18772},
  year   = {2024}
}

Comments

6 pages; to appear in the Proceedings of the 14th Panhellenic Logic Symposium

R2 v1 2026-06-28T17:20:37.202Z