Mazur 13 port: cancel_invertible_ideal

Proved

MazurProof.N13EffectiveDataCompatibility.cancel_invertible_ideal

by xuanji · Oct 9, 2026 · Mathlib 0df444a (Lean v4.33.1)

huang-flt-portmazur-full-torsionmazur-n13-portorder13

Supporting lemma cancel_invertible_ideal (namespace MazurProof.N13EffectiveDataCompatibility).

This lemma is one step of a machine-checked proof that the genus-two curve

Y^2 = X^6+4X^5+6X^4+2X^3+X^2+2X+1

(a model of $X_1(13)$ ) has no rational affine points other than the cusps $X\in\{0,-1\}$ , which gives the case $N=13$ of Mazur's torsion theorem. The proof is Xiang Huang's Lean development, ported to this Mathlib and split into one node per large lemma; definitions live in the layered entries MazurN13_L0, MazurN13_L1, ….

Preamble

import Mathlib

set_option backward.isDefEq.respectTransparency false
set_option backward.isDefEq.respectTransparency.types false
open scoped nonZeroDivisors

Formal statement

theorem MazurProof.N13EffectiveDataCompatibility.cancel_invertible_ideal {T K : Type*} [CommRing T] [IsDomain T] [Field K] [Algebra T K] [IsFractionRing T K] (I J U : Ideal T) (hU : IsUnit (U : FractionalIdeal T⁰ K)) (h : I * U = J * U) : I = J := by sorry

Source

Xiang Huang, FLT fork, https://github.com/xiangyazi24/FLT/blob/51bbb4f/FLT/Assumptions/MazurProof/N13EffectiveDataCompatibility.lean#L45

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