Entropy criterion for finiteness of the weak-disorder critical point

Let K(n)K(n) be the distribution of the renewal increments, and let βc\beta_c be the critical value separating weak disorder from strong disorder. Assume that the environment is unbounded from above.

Entropy criterion conjecture. The weak-disorder critical point is finite if and only if

βc<n1K(n)log1K(n)<.\beta_c<\infty\quad\Longleftrightarrow\quad\sum_{n\geq1}K(n)\log\frac{1}{K(n)}<\infty.

The criterion is proposed as a characterization of when a strong-disorder phase can occur in the heavy-tailed directed-polymer model. The surrounding discussion presents it as an unresolved question, particularly in the regime where the tail of KK is near the entropy threshold; no resolution is supplied in the source.

Sources & referencesView supporting material

Primary source

Roberto Viveros, “Directed Polymer for very heavy tailed random walks”, arXiv:2003.14280 (2020).

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