Exceptional polynomials
This page gives exceptional polynomials
according to the definition in my paper Distance to the
discriminant. They are all homogeneous polynomials in three
variables and therefore their zero locus are algebraic curves in the
projective plane. These polynomials maximize the distance to the discriminant for
the Bombieri norm, among polynomials of the same norm. As a consequence
(see the paper), they can all be written as sums of powers of linear
forms in the directions which correspond to critical points of P on
the unit sphere with the minimum absolute critical value.
This page presents two kinds of polynomials: exact
ones and numerical approximations. The
former are normalized to be at distance one to the discriminant,
while the latter are normalized to have Bombieri norm 1. In both cases,
we give two expressions:
- The original form arising from the construction of the curve.
- The writing as a sum of power of linear forms.
- For exact polynomials we have . For numerical polynomials, gives us an interesting error which tells us if the polynomial is optimized enough. For instance, if it is less than , we know that both polynomials have zero locus which are ambient-isotopic. When this is not the case, the optimization
process to maximize the distance to the discriminant is not
finished yet and the polynomial is marked with a ✖
sign. We stopped optimisation when we got the best polynomial with coefficients represented as double (64 bits IEEE 754 representation). When it is not the case, we will continue the optimisation. For the writing as a sum of power of linear forms, we give enough precision for the distance between the two polynomials to be accurate.
We provide images of the zero locus curves that can be zoomed and
dragged. The curve is projected onto a disc shown in light grey using
the stereographic projection of the hemisphere . We also highlight with a cross the critical points with the least critical absolute value on the unit sphere. These are the directions of the linear forms in the expression as a sum of linear forms to the power d.
| Degree |
Topology |
Remark |
Nb. of forms |
|
| Good |
Exact polynomials
Degree 2, ⟨1⟩ ✔
Degree 3, ⟨J ∐ 1⟩ ✔
Degree 4, ⟨4⟩ ✔
Degree 4, ⟨3⟩ ✔
Degree 6, ⟨10⟩ V1 ✔
This is a M-1 curve, but locally extremal. It is probably not in the same rigid isotopy class than the next one.
Degree 6, ⟨10⟩ V2 ✔
This is a M-1 curve, but locally extremal. It is probably not in the same rigid isotopy class than the previous one.
Approximated polynomials
Degree 5, ⟨𝐽 ∐ 6⟩ ✔
Degree 5, ⟨𝐽 ∐ 5⟩ ✔
Degree 6, ⟨9 ∐ 1⟨1⟩⟩ ✔
Degree 6, ⟨6 ∐ 1⟨2⟩⟩ ✔
Degree 6, ⟨2 ∐ 1⟨6⟩⟩ ✔
Degree 6, ⟨1 ∐ 1⟨9⟩⟩ ✔
Degree 6, ⟨5 ∐ 1⟨5⟩⟩ ✔
Degree 7, ⟨𝐽 ∐ 15⟩ ✔
Degree 8, ⟨18 ∐ 1⟨3⟩⟩ ✔
Degree 8, ⟨19⟩ ✔
Degree 9 ⟨J U 28⟩ ✖