Separation of survival and root-reinfection thresholds on strongly exponentially growing trees

Let TT be an infinite tree. Call a vertex vv essential if T{v}T\setminus\{v\} has at least two infinite components. Say that TT has strongly exponential growth if there is some integer r1r\geq1 such that, for every vTv\in T, there are at least three essential vertices ww at graph distance rr from vv. Let λ1\lambda_1 be the survival threshold and let λa\lambda_a be the threshold above which the root is reinfected at arbitrarily large times; together with λb\lambda_b, λ2\lambda_2, and λc\lambda_c, these are the critical values defined for the contact process above. Separation conjecture. For any tree with strongly exponential growth, either all the above critical values are zero, or

λ1λa.\lambda_1\neq\lambda_a.

The claim concerns whether survival can begin strictly before recurrent reinfection of the root on sufficiently branching trees. The source gives no resolution.

Sources & referencesView supporting material

Primary source

Robin Pemantle, “The Contact Process on Trees”, arXiv:math/0404046 (2004).

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