Zauner's maximal equiangular tight frame conjecture

For each dimension mm, let ρ1,ρ2,ρ3\rho_1,\rho_2,\rho_3 denote the three quantities defined in the paper, and let ρ(m)\rho(m) be the associated complex projection constant. Zauner's conjecture. For every m1m\geq 1,

λC(m)=1m(1+(m1)m+1).\lambda_\mathbb{C}(m)=\frac{1}{m}\left(1+(m-1)\sqrt{m+1}\right).

This is equivalent in the paper's framework to the existence of a complex maximal equiangular tight frame in every dimension. The formula is known in the listed dimensions m{1,,17,19,24,28,35,48}m\in\{1,\ldots,17,19,24,28,35,48\}, while the assertion for every dimension remains open.

Sources & referencesView supporting material

Primary source

Beata Deregowska and Barbara Lewandowska, “A simple proof of the Grunbaum conjecture”, arXiv:2206.09454 (2024).

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