Joyner's conjecture 4.3 on parameters of toric codes

Let C(E,D,X)\mathcal{C}(E,D,X) be the toric code associated to the 11-cycle EE, the TT-invariant Cartier divisor DD, and the toric variety XX. Assume that XX is a nonsingular toric variety of dimension rr, that

ψD(v)=minuPDMu,v\psi_D(v)=\min_{u\in P_D\cap M}\langle u,v\rangle

is strictly convex, and that deg(C)>deg(Dr)\deg(C)>\deg(D^r). Joyner's conjecture 4.3. If qq is sufficiently large, then every fH0(X,O(D))f\in\mathrm{H}^0(X,\mathcal{O}(D)) has at most nn zeros among the rational points of XX. Consequently,

kdimH0(X,O(D))=#(PDM),k\geq\dim\mathrm{H}^0(X,\mathcal{O}(D))=\#(P_D\cap M), dnr!#(PDM).d\geq n-r!\,\#(P_D\cap M).

Moreover, if n>r!#(PDM)n>r!\,\#(P_D\cap M), then

dimH0(X,O(D))=#(PDM).\dim\mathrm{H}^0(X,\mathcal{O}(D))=\#(P_D\cap M).

The paper gives a counterexample for q8q\geq8, so the conjecture is refuted.

Sources & referencesView supporting material

Primary source

Diego Ruano, “On the Parameters of r-dimensional Toric Codes”, arXiv:math/0512285 (2005).

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