Subgraph entropy

Document Type

Journal Article

Role

Author

Published In

Bulletin of the London Mathematical Society

Volume

58

Issue

6

Article Number

e70397

Publication Date

6-1-2026

Abstract

Given 𝑟 ⩾3, we prove that there exists 𝜆 >0 depending only on 𝑟 so that if 𝐺 is a metric graph of rank 𝑟 with metric entropy 1, then there exists a proper subgraph 𝐻 of 𝐺 with metric entropy at least 𝜆. This answers a question of the second two authors together with Rieck. We interpret this as a graph theoretic version of the Bers Lemma from hyperbolic geometry, and explain some connections to the pressure metric on the Culler–Vogtmann Outer Space.

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