Module

Coefficients_aeval_mem_lSpace_of_isHomogeneous.lean

Nyll.AlgebraicCurves.Cohomology.RiemannRoch.Coefficients_aeval_mem_lSpace_of_isHomogeneous
3 declarations indexed from sourceView source ↗

Pole bounds for the coefficients of a homogeneous substitution

This is the pole-control step of the Riemann--Roch proof of Tsen's theorem (Stacks Project, Tag 03RD). Multiplication is supplied by the existing divisor theory.

Declarations

AlgebraicCurve.mul_coefficients_mem_lSpace
Source context 3 commands

Surrounding namespaces, section variables, and local commands at this declaration.

noncomputable section
open scoped BigOperators
namespace AlgebraicCurve
theorem mul_coefficients_mem_lSpace
    {K F τ : Type*} [Field K] [Field F] [Algebra K F]
    {D E : Divisor K F} {p q : MvPolynomial τ F}
    (hp : p ∈ MvPolynomial.coeffsIn τ (LSpace D))
    (hq : q ∈ MvPolynomial.coeffsIn τ (LSpace E)) :
    p * q ∈ MvPolynomial.coeffsIn τ (LSpace (D + E))
AlgebraicCurve.pow_coefficients_mem_lSpace
Source context 3 commands

Surrounding namespaces, section variables, and local commands at this declaration.

noncomputable section
open scoped BigOperators
namespace AlgebraicCurve
theorem pow_coefficients_mem_lSpace
    {K F τ : Type*} [Field K] [Field F] [Algebra K F]
    {D : Divisor K F} {p : MvPolynomial τ F}
    (hp : p ∈ MvPolynomial.coeffsIn τ (LSpace D)) (n : ℕ) :
    p ^ n ∈ MvPolynomial.coeffsIn τ (LSpace (n • D))
AlgebraicCurve.coefficients_aeval_mem_lSpace_of_isHomogeneous

Substitution of polynomials with coefficients in L(D) into a degree-d homogeneous form with coefficients in L(E) has all coefficients in L(E + dD).

Source context 3 commands

Surrounding namespaces, section variables, and local commands at this declaration.

noncomputable section
open scoped BigOperators
namespace AlgebraicCurve
theorem coefficients_aeval_mem_lSpace_of_isHomogeneous
    {K F σ τ : Type*} [Field K] [Field F] [Algebra K F]
    {d : ℕ} (p : MvPolynomial σ F) (q : σ → MvPolynomial τ F)
    (D E : Divisor K F) (hhom : p.IsHomogeneous d)
    (hp : ∀ a : σ →₀ ℕ, p.coeff a ∈ LSpace E)
    (hq : ∀ i : σ, ∀ a : τ →₀ ℕ, (q i).coeff a ∈ LSpace D) :
    ∀ a : τ →₀ ℕ, (MvPolynomial.aeval q p).coeff a ∈ LSpace (E + d • D)