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Eulerian form of #2513: perturbed generalized Eulerian rows interlace - #2525

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PerAlexandersson merged 3 commits into
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theory/euler-orbit-cayley
Nov 10, 2026
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PerAlexandersson merged 3 commits into
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theory/euler-orbit-cayley

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Follow-up to #2524 (#2513, Eulerian form).

  • strictInterl_cayleyTransform_succ_of_roots_mem_Icc (in PolynomialValueEulerNumerator/Interlacing.lean): the Cayley transform preserves degree-raising interlacing p ≪ q, deg q = deg p + 1, for roots in [−1, 0]. The proof adjoins the root −1 to p (same degree-(n+1) transform) and reuses the same-degree theorem.
  • strictInterl_C_mul_add_C_mul_one_add_X_pow_of_recurrence: for s ≥ 1, c ≥ 1/2, E 0 = 1 and E (n+1) = (1 + (1 + s n) X) E n + s X (1 − X) E n', the rows c E n + (1 − c)(1 + X)^n interlace strictly; the splits theorem becomes a corollary.
  • cayleyEulerOrbit_eq_generalizedEulerian and strictInterl_C_mul_generalizedEulerian_add: the E n are generalizedEulerian s n.
  • orbitPerturbationRow_package also records the degree.

Downstream: closes the sorrys A141689_interlaces, A141689_prec, A141690_interlaces, A141690_prec in real-rooted-oeis-proofs (PR to follow).

Local checks: focused builds of touched modules and importers, runLinter, catalog audit, proof status; axioms propext, Classical.choice, Quot.sound.

🤖 Generated with Claude Code

PerAlexandersson and others added 3 commits November 10, 2026 18:53
strictInterl_cayleyTransform_succ_of_roots_mem_Icc: the Cayley transform preserves
degree-raising interlacing of polynomials with roots in [-1, 0] (adjoin the root -1, which does
not change the transform).  strictInterl_C_mul_add_C_mul_one_add_X_pow_of_recurrence: for
s >= 1 and c >= 1/2 the rows c E n + (1 - c) (1 + X)^n interlace strictly; the splits theorem
becomes a corollary.  orbitPerturbationRow_package now also records the degree.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
@PerAlexandersson
PerAlexandersson merged commit f41176d into main Nov 10, 2026
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PerAlexandersson deleted the theory/euler-orbit-cayley branch November 10, 2026 19:18
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