Hansen's parameter estimate for toric codes

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Let X=X(Δ)X=X(\Delta) be a complete toric variety of dimension rr, let GG be a TT-invariant Cartier divisor, let PGP_G be the polytope associated to GG, and let MM be the lattice associated to XX. For the toric evaluation code CL=CL(G,P,X)C_L=C_L(G,P,X), write nn for its length and dd for its minimum distance. Suppose XX is nonsingular and projective, and suppose there is an integer N>1N>1 such that

2N⋅vol⁡(PG)≤n≤2N2⋅vol⁡(PG).2N\cdot \operatorname{vol}(P_G)\leq n\leq 2N^2\cdot \operatorname{vol}(P_G).

Hansen's conjecture. If qq is sufficiently large, then every f∈L(G)=H0(X,O⁡(G))f\in L(G)=H^0(X,\operatorname{\mathcal O}(G)) has at most nn zeros in X(Fq)X(\mathbb{F}_q), and consequently

d≥n−2N⋅vol⁡(PG).d\geq n-2N\cdot \operatorname{vol}(P_G).

The meaning of sufficiently large may depend on XX, PP, and GG, but not on ff. The estimate was conjecturally proposed for toric codes and verified computationally for many examples; its general validity is not resolved by the supplied text.

References

Primary source

David Joyner, “Toric codes over finite fields”, arXiv:math/0208155 (2003).

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