Quadratic Twist Point Equiv map
WeierstrassCurve.quadraticTwistPointEquiv_map
Plain-language statement
Naturality of quadraticTwistPointEquiv in M: the isomorphisms on M-points over varying M ⊇ L are all induced by a single isomorphism of curves over L, so they commute with the maps on points induced by any L-algebra homomorphism.
Exact Lean statement
theorem quadraticTwistPointEquiv_map {N : Type*} [Field N] [Algebra K N] [Algebra L N]
[IsScalarTower K L N] [DecidableEq N] (f : M →ₐ[L] N)
(P : ((E.quadraticTwist L)⁄M).Point) :
E.quadraticTwistPointEquiv L N (Affine.Point.map f P) =
Affine.Point.map f (E.quadraticTwistPointEquiv L M P)Formal artifact
Lean source
theorem quadraticTwistPointEquiv_map {N : Type*} [Field N] [Algebra K N] [Algebra L N] [IsScalarTower K L N] [DecidableEq N] (f : M →ₐ[L] N) (P : ((E.quadraticTwist L)⁄M).Point) : E.quadraticTwistPointEquiv L N (Affine.Point.map f P) = Affine.Point.map f (E.quadraticTwistPointEquiv L M P) := by -- The base-changed change of variables over `N` is the image under `f` of that over `M`. have hu : (((E.quadraticTwistVarChange L).baseChange N).u : N) = f (((E.quadraticTwistVarChange L).baseChange M).u : M) := by simp only [VariableChange.baseChange, VariableChange.map, Units.coe_map, MonoidHom.coe_coe] exact (f.commutes _).symm have hr : ((E.quadraticTwistVarChange L).baseChange N).r = f ((E.quadraticTwistVarChange L).baseChange M).r := (f.commutes _).symm have hs : ((E.quadraticTwistVarChange L).baseChange N).s = f ((E.quadraticTwistVarChange L).baseChange M).s := (f.commutes _).symm have ht : ((E.quadraticTwistVarChange L).baseChange N).t = f ((E.quadraticTwistVarChange L).baseChange M).t := (f.commutes _).symm rcases P with _ | ⟨x, y, h⟩ · simp [← Affine.Point.zero_def] · simp only [quadraticTwistPointEquiv, AddEquiv.trans_apply, Affine.Point.equivOfEq_some, Affine.Point.equivVariableChange_some, Affine.Point.map_some] refine Affine.Point.some_eq_some (E.baseChange N) ?_ ?_ · simp only [map_add, map_mul, map_pow, hu, hr] · simp only [map_add, map_mul, map_pow, hu, hs, ht]- Project
- Fermat's Last Theorem
- License
- Apache-2.0
- Commit
- 8dd808888295
- Source
- FLT/KnownIn1980s/EllipticCurves/QuadraticTwists/QuadraticTwists.lean:665-687
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