The dimension formulas for the codes C(1,q) and C(2,q) over odd prime powers

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Let qq be an odd prime power, and let C(1,q)C(1,q) and C(2,q)C(2,q) be the codes defined from the incidence structures in the paper. Their dimensions are the integers dim⁡C(1,q)\dim C(1,q) and dim⁡C(2,q)\dim C(2,q). Dimension conjecture.

dim⁡C(1,q)=12q3−q2+32q−1,\dim C(1,q)=\frac{1}{2}q^3-q^2+\frac{3}{2}q-1, dim⁡C(2,q)=12q3−52q2+92q−72.\dim C(2,q)=\frac{1}{2}q^3-\frac{5}{2}q^2+\frac{9}{2}q-\frac{7}{2}.

These formulas were obtained by interpolation from computed tables and are verified in the source for every odd prime power qq with 5≤q≤315\leq q\leq31; their validity beyond that range is not established.

References

Primary source

Alain Couvreur, “Incidence structures from the blown-up plane and LDPC codes”, arXiv:1004.3774 (2011).

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