Hollmann's pseudocyclicity conjecture for the Frobenius fusion scheme

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Let q=2mq=2^m, let E{\cal E} be the set of exterior lines to a fixed nonsingular conic in PG(2,q){\rm PG}(2,q), and let (E,{Γa})({\cal E},\{\Gamma_a\}) be the elliptic association scheme. For a∈T0∗a\in {\bf T}_0^*, define the Frobenius orbit

Ca={a,a2,a4,…,a2m−1}C_a=\{a,a^2,a^4,\ldots,a^{2^{m-1}}\}

and set

Δa=⋃i∈CaΓi.\Delta_a=\bigcup_{i\in C_a}\Gamma_i.

Let R{\cal R} be a set of representatives for the Frobenius orbits on T0∗{\bf T}_0^*. The fusion scheme (E,{Δa})({\cal E},\{\Delta_a\}) is obtained by merging the classes of the elliptic scheme along these orbits.

Hollmann's conjecture. If mm is an odd prime, then (E,{Δa})({\cal E},\{\Delta_a\}) is pseudocyclic.

When mm is prime, each nontrivial Frobenius orbit has size mm, so the fusion scheme has equal nontrivial valencies. The conjecture asserts the remaining condition needed for pseudocyclicity; the source gives no resolution.

References

Primary source

Henk D. L. Hollmann and Qing Xiang, “Pseudocyclic association schemes arising from the actions of PGL(2,2^m) and PΓL(2,2^m)”, arXiv:math/0503570 (2005).

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