Proof of `Minors of acyclic graphs are acyclic`
groundedproofs/Lax68Proofs/ForestMinors.lean · lax-68
What this proof establishes
no assumptions
Assuming the claims on the left, the claim on the right holds — checked by the archive's pipeline. Proof code is not displayed here.
Description
Every edge of an acyclic graph is a bridge. If an edge of the minor had an alternative route between its endpoints, that route would lift through the connected branch sets after deleting a corresponding edge of the original graph. This contradicts that edge being a bridge.