Davydov–Marcugini–Pambianco orbit-count conjecture for generic lines in PG(3,q)PG(3,q)

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Let qq be a power of 33, let G=PGL2(q)G=PGL_2(q) act on the lines of PG(3,q)PG(3,q), and let CC be the twisted cubic. A line is generic if it neither intersects CC nor lies in any osculating plane of CC; write O6\mathcal{O}_6 for the class of generic lines. Davydov–Marcugini–Pambianco's conjecture. The number of GG-orbits of generic lines of PG(3,q)PG(3,q) is 2q−32q-3, of which there are q/3q/3, q−1q-1, and (2q−6)/3(2q-6)/3 orbits of sizes ∣G∣|G|, ∣G∣/2|G|/2, and ∣G∣/4|G|/4, respectively. This conjecture gives the proposed classification of the generic-line class O6\mathcal{O}_6 into GG-orbits in characteristic 33, a case that had remained open after the corresponding problems in characteristics different from 22 and 33, and in characteristic 22, were solved.

References

Primary source

Krishna Kaipa and Puspendu Pradhan, “On the PGL_2(q)-orbits of lines of PG(3,q) and binary quartic forms in characteristic three”, arXiv:2508.11229 (2025).

Additional references

2 papers in this index state this conjecture (2023–2025). The statement above is taken from the most recent of them; the others are arXiv:2312.07118.

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