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feat: straddle-set no-cross + not-internal facts — #2965#2982

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feat/straddle-cross-facts-2965
May 26, 2026
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feat: straddle-set no-cross + not-internal facts — #2965#2982
phasetr merged 2 commits into
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feat/straddle-cross-facts-2965

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@phasetr phasetr commented May 26, 2026

Part of #2965.

Two graph-level facts about the straddle (cut) edge set of induce_sum_map_sumCompl_eq_deleteEdges (#2979), in SumGraph.lean:

Pure adjacency (no Fintype/instance risk), bridging #2979/#2981/#2978 toward the bond-deletion → isolated-component capstone via the working inducedGraph route.

lake build IsingModel.SumGraph green, sorry 0, file linter-clean, tex compiles.

🤖 Generated with Claude Code

phasetr and others added 2 commits May 27, 2026 01:00
Add two graph-level facts about the straddle (cut) edge set of
induce_sum_map_sumCompl_eq_deleteEdges:

- straddle_not_mem_of_same_side: p a ↔ p b ⇒ s(a,b) ∉ straddle (the deleted set
  contains no same-side edge), feeding inducedGraph_deleteEdges_eq_of_not_internal.
- deleteEdges_straddle_no_cross: p a, ¬p b ⇒ ¬(G.deleteEdges {straddle}).Adj a b
  (the bond-deleted graph disconnects the two sides), the no-cross hypothesis for
  correlation_inducedGraph_union_inl_of_no_cross applied to G.deleteEdges {straddle}.

Pure adjacency facts (no Fintype), bridging #2979/#2981/#2978 toward the
bond-deletion → isolated-component capstone via the working inducedGraph route.

Part of #2965

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
@phasetr phasetr merged commit aa6ffd3 into main May 26, 2026
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phasetr added a commit that referenced this pull request May 26, 2026
…apstone, Finset route) — #2965 (#2983)

* feat: bond-deleted correlation = isolated induced subgraph (Finset route) (Part of #2965)

* feat: bond-deleted correlation = isolated induced subgraph (Phase A capstone, Finset route)

Add correlation_inducedGraph_deleteEdges_union_inl: for S ⊆ W, deleting the cut
edges between S and Sᶜ gives

  correlation (inducedGraph (G.deleteEdges {straddle S}) (S ∪ Sᶜ)) p
    ((A.map inl).map union) = correlation (inducedGraph G S) p A

— the bond-deleted model's correlation of an S-supported observable equals the
correlation in the isolated induced subgraph on S of the original model.

Assembled from correlation_inducedGraph_union_inl_of_no_cross (#2978) ∘
correlation_congr_of_eq (inducedGraph_deleteEdges_eq_of_not_internal, #2981),
with no-cross/not-internal hypotheses discharged by deleteEdges_straddle_no_cross
/ straddle_not_mem_of_same_side (#2982). Reuses the working inducedGraph/Finset
machinery, sidestepping the Equiv.sumCompl instance pathology (#2980) entirely.

This is the Issue #2965 Phase A component-factorization capstone: combined with
the ball-boundary bond-deletion increment correlation_sub_deleteEdges_le_derivBound
(#2974), it yields the per-stage exhaustion increment bound.

Part of #2965

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>
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