Linear-time inverse positive definite Hankel factorization conjecture

From papers

Let HRn×n\mathbf{H} \in \mathbb{R}^{n\times n} be a positive definite Hankel matrix with bit complexity \ell and condition number bounded by 22^\ell. An inverse symmetric positive factorization algorithm should find a representation of a matrix B\mathbf{B} with nn rows, O~(n)\tilde{O}(n) columns, and bit complexity \ell in time O~(nω/2)\tilde{O}(n^{\omega/2} \cdot \ell) such that

H1BBF<12.\left\|\mathbf{H}^{-1}-\mathbf{B}\mathbf{B}^*\right\|_{\operatorname{F}}<\frac{1}{2^{\ell}}.

This conjecture would provide a positive-semidefinite symmetric factorization for the inverse of a positive definite Hankel matrix within the stated subquadratic running time. It complements the paper's difference-of-positive-factorizations approach for Hankel matrices and their inverses; the supplied text gives no resolution of this conjecture.

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Sources & referencesView supporting material

Primary source

Mehrdad Ghadiri, “On Symmetric Factorizations of Hankel Matrices”, arXiv:2307.00805 (2023).

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