The Gelfand-transform criterion for elementary generation in Banach algebras

Let RR be a commutative, semisimple, unital complex Banach algebra with maximal ideal space XRX_R equipped with the weak-\ast topology induced from R:=L(R;C)R^*:=\mathcal{L}(R;\mathbb{C}). Let ^:RC(XR;C)\widehat{\cdot}:R\to C(X_R;\mathbb{C}) be the Gelfand transform. For FSLn(R)F\in SL_n(R), let F^\widehat F be the matrix obtained by applying the Gelfand transform to its entries, and let π(F^)\pi(\widehat F) denote the homotopy class of the map φF^(φ):XRSLn(C)\varphi\mapsto\widehat F(\varphi):X_R\to SL_n(\mathbb{C}). Write En(R)E_n(R) for the subgroup of SLn(R)SL_n(R) generated by elementary matrices.

Gelfand-transform criterion. FSLn(R)F\in SL_n(R) belongs to En(R)E_n(R) if and only if

π(F^)=0.\pi(\widehat F)=0.

This asks whether elementary generation over a commutative semisimple Banach algebra is characterized exactly by the null-homotopy of the associated Gelfand-transform map. The supplied text presents it as a question/conjecture; no resolution is given here.

Sources & referencesView supporting material

Primary source

Amol Sasane, “Factorization in SL_n(R) with elementary matrices when R is the disk algebra and the Wiener algebra”, arXiv:1405.5006 (2014).

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