The Lemmens–Seidel conjecture for equiangular lines at angle arccos(1/5)

Let Nα(r)N_{\alpha}(r) be the maximum number of a system of equiangular lines in Rr\mathbb{R}^r with common angle arccosα\arccos\alpha. The Lemmens–Seidel conjecture concerns the case α=15\alpha=\frac{1}{5}. Lemmens–Seidel conjecture. The maximum cardinality of a system of equiangular lines with angle arccos15\arccos\frac{1}{5} in Rr\mathbb{R}^r is 276276 for 23r18523 \leqslant r \leqslant 185, and 3r32\lfloor \frac{3r-3}{2}\rfloor for r185r \geqslant 185. Neumaier proved the assertion for sufficiently large rr, and the paper states that it completely solves the conjecture.

Sources & referencesView supporting material

Primary source

Meng-Yue Cao, Jack H, Koolen, Yen-Chi Roger Lin and Wei-Hsuan Yu, “The Lemmens-Seidel conjecture and forbidden subgraphs”, arXiv:2003.07511 (2020).

Additional references

2 papers in this index state this conjecture (2018–2020). The statement above is taken from the most recent of them; the others are arXiv:1807.06249.

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