Bukh's conjecture on spherical codes with separated negative inner products

Let β(0,1)\beta\in(0,1) be fixed, let α1,,αk\alpha_1,\dots,\alpha_k be any kk real numbers, and let a spherical LL-code be a finite non-empty set of unit vectors in Rn\mathbb{R}^n whose pairwise inner products lie in LL. Bukh's conjecture. Every spherical [1,β]{α1,,αk}[-1,-\beta]\cup\{\alpha_1,\dots,\alpha_k\}-code in Rn\mathbb{R}^n has size at most

cβ,knk,c_{\beta,k}n^k,

for some constant cβ,kc_{\beta,k} depending only on β\beta and kk. Bukh had proved the corresponding linear bound when the positive part consists of one value. The conjecture generalizes polynomial upper bounds of Delsarte, Goethals and Seidel and remains open based on the supplied information.

Sources & referencesView supporting material

Primary source

Igor Balla, Felix Dräxler, Peter Keevash and Benny Sudakov, “Equiangular Lines and Spherical Codes in Euclidean Space”, arXiv:1606.06620 (2017).

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