English

The Frog Model on $\mathbb{Z}$ with Discrete Weibull Lifetimes and Random Parameter $p$

Probability 2026-01-23 v1

Abstract

We study the frog model on Z\mathbb{Z} with particle wise discrete Weibull lifetimes. Each particle has an i.i.d. survival parameter π(0,1)\pi\in(0,1); conditionally on π=p\pi=p, its lifetime Ξ\Xi satisfies P(Ξkπ=p)=pkγ,kN0,γ>0. P(\Xi\ge k\mid \pi=p)=p^{k^{\gamma}},\qquad k\in\mathbb{N}_0,\gamma>0. The law of π\pi has right edge density fπ(u)(1u)β1,L((1u)1)(u1), f_\pi(u)\sim(1-u)^{\beta-1},L\big((1-u)^{-1}\big)\qquad (u\uparrow 1), with β>0\beta>0 and LL slowly varying; let η\eta denote the common law of the i.i.d. initial occupation numbers {ηx}xZ\{\eta_x\}_{x\in\mathbb{Z}}. The survival parameter distribution strictly extends the Beta family, while the lifetime distribution extends the geometric case. We prove a sharp extinction and survival dichotomy with the γ\gamma-dependent threshold βc:=12γ. \beta_c:=\frac{1}{2\gamma}. If β>βc\beta>\beta_c and E(η)<E(\eta)<\infty, the process becomes extinct almost surely; if β<βc\beta<\beta_c and P(η=0)<1P(\eta=0)<1, it survives with positive probability. At the boundary β=βc\beta=\beta_c we provide explicit criteria in terms of lim sup/lim inf\limsup/\liminf of L(n2γ)L(n^{2\gamma}). The case γ=1\gamma=1 (geometric lifetimes) recovers the benchmark βc=12\beta_c=\frac{1}{2} and the critical refinements previously obtained for random geometric lifetimes.

Keywords

Cite

@article{arxiv.2601.15526,
  title  = {The Frog Model on $\mathbb{Z}$ with Discrete Weibull Lifetimes and Random Parameter $p$},
  author = {J. H. Ramírez González and Gustavo O. Carvalho and Fábio P. Machado},
  journal= {arXiv preprint arXiv:2601.15526},
  year   = {2026}
}

Comments

23 pages, 2 figures

R2 v1 2026-07-01T09:15:01.373Z