English

Multiple points on the boundaries of Brownian loop-soup clusters

Probability 2025-05-13 v3 Mathematical Physics math.MP

Abstract

For a Brownian loop soup with intensity c(0,1]c\in(0,1] in the unit disk, we show that almost surely, the set of simple (resp. double) points on any portion of boundary of any of its clusters has Hausdorff dimension 2ξc(2)2-\xi_c(2) (resp. 2ξc(4)2-\xi_c(4)), where ξc(k)\xi_c(k) is the generalized disconnection exponent computed in arxiv:1901.05436. As a consequence, when the dimension is positive, such points are a.s. dense on every boundary of every cluster. There are a.s. no triple points on the cluster boundaries. As an intermediate result, we establish a separation lemma for Brownian loop soups, which is a powerful tool for obtaining sharp estimates on non-intersection and non-disconnection probabilities in the setting of loop soups. In particular, it allows us to define a family of generalized intersection exponents ξc(k,λ)\xi_c(k, \lambda), and show that ξc(k)\xi_c(k) is the limit as λ0\lambda\searrow 0 of ξc(k,λ)\xi_c(k, \lambda).

Keywords

Cite

@article{arxiv.2205.11468,
  title  = {Multiple points on the boundaries of Brownian loop-soup clusters},
  author = {Yifan Gao and Xinyi Li and Wei Qian},
  journal= {arXiv preprint arXiv:2205.11468},
  year   = {2025}
}

Comments

58 pages, 12 figures, to appear in AOP

R2 v1 2026-06-24T11:25:58.117Z