## The Annals of Applied Probability

- Ann. Appl. Probab.
- Volume 27, Number 3 (2017), 1678-1701.

### On the capacity functional of the infinite cluster of a Boolean model

Günter Last, Mathew D. Penrose, and Sergei Zuyev

#### Abstract

Consider a Boolean model in $\mathbb{R}^{d}$ with balls of random, bounded radii with distribution $F_{0}$, centered at the points of a Poisson process of intensity $t>0$. The capacity functional of the infinite cluster $Z_{\infty}$ is given by $\theta_{L}(t)=\mathbb{P}\{Z_{\infty}\cap L\ne\varnothing \}$, defined for each compact $L\subset\mathbb{R}^{d}$.

We prove for any fixed $L$ and $F_{0}$ that $\theta_{L}(t)$ is infinitely differentiable in $t$, except at the critical value $t_{c}$; we give a Margulis–Russo-type formula for the derivatives. More generally, allowing the distribution $F_{0}$ to vary and viewing $\theta_{L}$ as a function of the measure $F:=tF_{0}$, we show that it is infinitely differentiable in all directions with respect to the measure $F$ in the supercritical region of the cone of positive measures on a bounded interval.

We also prove that $\theta_{L}(\cdot)$ grows at least linearly at the critical value. This implies that the critical exponent known as $\beta$ is at most 1 (if it exists) for this model. Along the way, we extend a result of Tanemura [*J. Appl. Probab.* **30** (1993) 382–396], on regularity of the supercritical Boolean model in $d\geq3$ with fixed-radius balls, to the case with bounded random radii.

#### Article information

**Source**

Ann. Appl. Probab., Volume 27, Number 3 (2017), 1678-1701.

**Dates**

Received: January 2016

Revised: July 2016

First available in Project Euclid: 19 July 2017

**Permanent link to this document**

https://projecteuclid.org/euclid.aoap/1500451238

**Digital Object Identifier**

doi:10.1214/16-AAP1241

**Mathematical Reviews number (MathSciNet)**

MR3678482

**Zentralblatt MATH identifier**

1373.60160

**Subjects**

Primary: 60K35: Interacting random processes; statistical mechanics type models; percolation theory [See also 82B43, 82C43]

Secondary: 60D05: Geometric probability and stochastic geometry [See also 52A22, 53C65]

**Keywords**

Continuum percolation Boolean model infinite cluster capacity functional percolation function Reimer inequality Margulis–Russo-type formula

#### Citation

Last, Günter; Penrose, Mathew D.; Zuyev, Sergei. On the capacity functional of the infinite cluster of a Boolean model. Ann. Appl. Probab. 27 (2017), no. 3, 1678--1701. doi:10.1214/16-AAP1241. https://projecteuclid.org/euclid.aoap/1500451238