The integer grid gives distinct bounded-height rational points on the irreducible projective closure. This is the geometric input to CCDN Proposition 5, including the stated degree and the exact grid size.
theorem
CCDN.integer_grid_le_projective_count
{n d : ℕ}
(f : MvPolynomial (Fin n) ℚ)
(hd : f.totalDegree ≤ d)
(s : Finset ℤ)
{B : ℝ}
(hB : 1 ≤ B)
(hsB : ∀ a ∈ s, |↑a| ≤ B)
(hfzero : ∀ (z : IntPoint n), (∀ (j : Fin n), z j ∈ s) → (MvPolynomial.eval (rationalPoint z)) f = 0)
:
A finite integral grid injects into projective space by z↦[1:z].
theorem
CCDN.projective_closure_absolute_irreducible
{n d : ℕ}
(f : MvPolynomial (Fin n) ℚ)
(hd : f.totalDegree = d)
(hf : AbsolutelyIrreducibleRat f)
:
(scaledHomogenize d 1 f).IsHomogeneous d ∧ (scaledHomogenize d 1 f).totalDegree = d ∧ AbsolutelyIrreducibleRat (scaledHomogenize d 1 f)
The homogenization of an absolutely irreducible rational polynomial of total degree d is a
form of degree d that is again absolutely irreducible.
theorem
CCDN.exists_projective_grid_lower_bound
(d : ℕ)
(hd : 4 ≤ d)
:
∃ (F : MvPolynomial (Fin 3) ℚ),
F.IsHomogeneous d ∧ F.totalDegree = d ∧ AbsolutelyIrreducibleRat F ∧ ((d - 1) / 2 + 1) ^ 2 ≤ projectiveCount (projectiveZeroLocus F) ↑((d - 1) / 2 - (d - 1) / 4)
For d≥4, the precise asymmetric integer grid used in Section 6 supplies (floor((d−1)/2)+1)² distinct projective points at the paper's chosen height.
theorem
CCDN.exists_projective_two_point_lower_bound
(d : ℕ)
(hd : 0 < d)
:
∃ (F : MvPolynomial (Fin 3) ℚ),
F.IsHomogeneous d ∧ F.totalDegree = d ∧ AbsolutelyIrreducibleRat F ∧ 2 ≤ projectiveCount (projectiveZeroLocus F) 1
Every positive degree has an absolutely irreducible projective model with at least two rational points of height one. This covers d=1,2,3 in Proposition 5.