Uniqueness of the complex 4×84\times 8 equiangular tight frame

A complex 4×84\times8 ETF is an equiangular tight frame represented by a matrix with four rows and eight complex unit-norm columns. Two ETFs are switching equivalent when they are identified under the switching operations used for ETF signature matrices.

4×84\times8 uniqueness conjecture. There exists a unique complex 4×84\times8 ETF up to switching equivalence.

The paper reports a failed initial Gröbner-basis attempt and numerical evidence supporting the claim, including trials whose rounded signature matrices produced the same ETF. The conjecture is not proved in the source.

Sources & referencesView supporting material

Primary source

Joseph W. Iverson, John Jasper and Dustin G. Mixon, “More on the optimal arrangement of 2d lines in C^d”, arXiv:2410.17379 (2024).

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