A polynomial matrix with dependent columns at every integer value has a polynomial kernel vector that remains nonzero at zero. A common power of X is removed from a kernel vector after its rational denominators are cleared.
theorem
CCDN.polynomial_matrix_kernel_nonzero_at_zero
{K : Type u_1}
{ι : Type u_2}
{κ : Type u_3}
[Field K]
[CharZero K]
[Finite ι]
[Fintype κ]
(A : Matrix ι κ (Polynomial K))
(hA : ∀ (k : ℕ), ¬Function.Injective ⇑(A.map ⇑(Polynomial.evalRingHom ↑k)).mulVecLin)
:
∃ (v : κ → Polynomial K), A.mulVec v = 0 ∧ ∃ (j : κ), Polynomial.eval 0 (v j) ≠ 0
If every integer specialization has dependent columns, there is a polynomial relation whose constant coefficient vector is nonzero.