The matrix inverse realization conjecture for noncommutative rational functions

Let A\mathcal A be the algebra under consideration and let L1L\geq 1. For an invertible matrix AAL×L\mathfrak A\in\mathcal A^{L\times L}, write

A=(aij)1i,jL,A1=(bij)1i,jL.\mathfrak A=(\mathfrak a_{ij})_{1\leq i,j\leq L},\qquad \mathfrak A^{-1}=(\mathfrak b_{ij})_{1\leq i,j\leq L}.

Matrix inverse realization conjecture. Each entry of A1\mathfrak A^{-1} is a noncommutative rational expression in the entries of A\mathfrak A: there exist noncommutative rational expressions SijS_{ij}, for 1i,jL1\leq i,j\leq L, such that

(a11,,aLL)domA(Sij)(\mathfrak a_{11},\ldots,\mathfrak a_{LL})\in\operatorname{dom}_{\mathcal A}(S_{ij})

and

bij=Sij(a11,,aLL),1i,jL.\mathfrak b_{ij}=S_{ij}(\mathfrak a_{11},\ldots,\mathfrak a_{LL}),\qquad 1\leq i,j\leq L.

This assertion is stated as equivalent to the preceding conjecture concerning inversion of matrix-valued noncommutative rational functions; its resolution would provide rational-expression realizations of inverse matrix entries over the algebra.

Sources & referencesView supporting material

Primary source

Motke Porat and Victor Vinnikov, “Realizations of non-commutative rational functions around a matrix centre, II: The lost-abbey conditions”, arXiv:2009.08527 (2022).

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