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Inhomogeneous contact processes on trees
Authors:C Chris Wu
Institution:(1) Department of Mathematics, Penn State University, Beaver Campus, 15061 Monaca, Pennsylvania
Abstract:We consider an inhomogeneous contact process on a tree 
$$\mathbb{T}_k $$
of degreek, where the infection rate at any site isλ, the death rate at any site in 
$$S \subset \mathbb{T}_k $$
isδ (with 0 <δ ⩽ 1) and that at any site in 
$$\mathbb{T}_k  - S$$
is 1. Denote by 
$$\lambda _c (\mathbb{T}_k )$$
the critical value for thehomogeneous model (i.e.,δ=1) on 
$$\mathbb{T}_k $$
and byϑ(δ, λ) the survival probability of the inhomogeneous model on 
$$\mathbb{T}_k $$
. We prove that whenk > 4, if 
$$S = \mathbb{T}_\sigma  $$
, a subtree embedded in 
$$\mathbb{T}_k $$
, with 1 ⩽σ ⩽ √k, then three existsδ c σ strictly between ( 
$$\lambda _c (\mathbb{T}_k )/\lambda _c (\mathbb{T}_\sigma  )$$
) and 1 such that ( 
$$\theta (\delta ,\lambda _c (\mathbb{T}_k )) = 0$$
) whenδ >δ c σ andϑ(δ, λ c( 
$$\theta (\delta , \lambda _c (\mathbb{T}_k )) > 0$$
) > 0 whenδ <δ c σ ; ifS={o}, the origin of 
$$\theta (\delta , \lambda _c (\mathbb{T}_k )) = 0$$
, then 
$$\theta (\delta , \lambda _c (\mathbb{T}_k )) = 0$$
for anyδ ε (0, 1).
Keywords:Contact process  inhomogeneity  trees
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