Ye–Lim's universal Toeplitz factorization conjecture

Let nNn\in\mathbb{N} and let MCn×nM\in\mathbb{C}^{n\times n}. Write Toep(M)\mathrm{Toep}(M) for the minimal number of Toeplitz matrices whose product is MM, and let Toepn\mathrm{Toep}_n be the maximum of Toep(M)\mathrm{Toep}(M) over all n×nn\times n matrices.

Ye–Lim's conjecture. For all nNn\in\mathbb{N},

Toepn=n2+1.\mathrm{Toep}_n=\left\lfloor\frac{n}{2}\right\rfloor+1.

This asserts that the generic upper bound established by Ye and Lim holds for every matrix, not merely for generic matrices. The paper notes that the conjecture is true for n=1,2n=1,2 but is disproved for n=3n=3; the proposed replacement in odd dimensions appears later in the paper.

Sources & referencesView supporting material

Primary source

Ignacio García-Marco, Irene Márquez-Corbella and Daniel Seco, “On the minimum number of Toeplitz factors of a matrix”, arXiv:2506.16432 (2025).

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