Removing the exceptional fibers #
After denominator clearing, the generic-fiber argument gives coefficient vanishing away from one analytic bad factor. This file packages the pure pointwise step: fiber rigidity makes every lower-degree coefficient zero on the good locus, so multiplying by the bad factor extends the conclusion over the exceptional locus as well.
theorem
LocalComplexGeometry.eventually_mul_coefficient_eq_zero_of_vanishes_on_good_fibers
{n e : ℕ}
(he : 0 < e)
(Z : ComplexEuclidean n → Prop)
(D : ComplexEuclidean n → ℂ)
(q : ComplexEuclidean n → Polynomial ℂ)
(b : Fin e → ComplexEuclidean n → ℂ)
(hgood :
∀ᶠ (z : ComplexEuclidean n) in nhds 0, Z z →
D z ≠ 0 →
q z ≠ 0 ∧ (q z).Separable ∧ (q z).natDegree = e ∧ ∀ (w : ℂ), Polynomial.eval w (q z) = 0 → Polynomial.eval w (remainderPolynomialAt b z) = 0)
:
If a degree-< e polynomial vanishes on all roots of a separable
degree-e fiber whenever D is nonzero, then every coefficient multiplied
by D vanishes, including on the exceptional fibers where D = 0.
theorem
LocalComplexGeometry.localSetGerm_le_germZeroLocus_mul_of_eventually
{n : ℕ}
(Z : LocalSetGerm n)
(Zrep : ComplexEuclidean n → Prop)
(D c : ComplexEuclidean n → ℂ)
(hD : AnalyticAt ℂ D 0)
(hc : AnalyticAt ℂ c 0)
(hZ : Z = ↑Zrep)
(hvanish : ∀ᶠ (z : ComplexEuclidean n) in nhds 0, Zrep z → D z * c z = 0)
:
Turn the representative-level product-vanishing conclusion into the corresponding inclusion of local set germs.