Minimal polynomial degree for geometric separation of torus-knot subsets on the standard torus
Determine, for each integer p ≥ 1, the minimal integer degree d of a polynomial P(z,w) such that P(0,0) = 0 and the level sets H_λ = {(z,w) ∈ C^2 : P(z,w) = λ} are disjoint from K_p = {(e^{ipθ}, e^{-iθ}) : 0 ≤ θ ≤ 2π} for all λ ≥ 0, thereby showing that (0,0) does not belong to the geometric d-polynomial hull of K_p.
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So, at least for p ≤ 4, one can test that (0,0) is not in the geometric polynomial hull of Kp using polynomials of degree 2. We do not believe that this holds for larger p, but we are not able to find the lowest degree of polynomials for even such a simple case.
— Polynomial convexity with degree bounds
(2403.14529 - Slapar, 21 Mar 2024) in Example 7, Section 2