OAI/Geometry/HyperbolicGroups/TreeSubpairingLift.lean
1 declarations, 0 contain sorry, 0 declared as axioms
- theorem
OAI.HyperbolicObstruction.PictureSwitch.PictureMap.lift_spanning_treeline 25Source documentation
Every spanning tree of the actual underlying graph lifts to a genuine one-boundary dart subpairing. Kruskal is applied ONLY to actual copies of its own edges; connectedness then forces equality with the selected tree. This permits a shortest-path tree, rather than an arbitrary-radius tree.
theorem lift_spanning_tree (T : SimpleGraph M.GraphVertex) (hle : T ≤ M.underlyingGraph) (hT : T.IsTree) : ∃ q : Perm D, ∃ hq : ∀ x, q x = x ∨ q x = M.edge x, SameCycle.setoid M.vertex ⊔ SameCycle.setoid q = ⊤ ∧ cycles (M.vertex*q) = 1 ∧ M.subpairingGraph q (M.subpairing_sq q hq) = T := by …