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.

Background

In Section 2 the paper studies polynomial convexity with degree bounds for subsets of the standard Lagrangian torus in C2. For the family K_p = {(e{ipθ}, e{-iθ})}, the author exhibits, for p ≤ 4, explicit quadratic polynomials whose level sets avoid K_p for all nonnegative levels while passing through (0,0), which demonstrates that (0,0) is not in the geometric degree-2 polynomial hull of K_p.

The author suggests this behavior may fail for larger p but leaves open the task of identifying the optimal (lowest) degree required to achieve such a separation for general p.

References

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