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Library · hunts/weil_propagation/c4_s2/cutoff/BRIEF.md

Brief: cutoff/, gap (c), product-ball cutoff against the global module cutoff

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You own hunts/weil_propagation/c4_s2/cutoff/ and write nowhere else. Time box: 2 hours of work from your start. This is proof work and can run indefinitely; at the box, write RESULTS.md with the exact state and stop.

The gap

The factorization Π_S = S_∞ ⊗ P_2 + 1 ⊗ (1 − P_2) (theory §7.3 item 2) holds for product cutoffs. Connes' semilocal formula (arXiv:2602.04022 eq. (22)) cuts off by the global module |x|_S, which does not factor. The passage from the product-ball cutoff to the module cutoff is unproved. two_adic/ builds T_S with the product-ball cutoff; your result decides what that T_S says about the formula as Connes states it.

Inputs

Tasks, in order

  1. State both cutoffs exactly for S = {∞, 2} on windows c ∈ [2, 3), and the trace term each one defines. Milestone 1: status message.
  2. Prove that the two give the same T_S on these windows, or bound the difference (operator norm, or trace, on the window space), or state the gap exactly: which term fails to transfer, and why.
  3. If a matrix comparison is cheap, compute the difference on the mission cells in the shared basis, reusing two_adic/'s functions read-only through imports, never by editing their files. If it is not cheap, say what it would cost.
  4. If a clean lemma comes out, you may state it in Lean and check it with AXLE; grade it kernel-checked for exactly that lemma.

Your RESULTS.md must say which of prove / bound / gap you reached, with its grade.

Standing rules (identical in all four briefs)