Concrete Barriers to Quantifier Elimination in Finite-Dimensional C*-algebras

Christopher J. Eagle; Todd Schmid

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arXiv · 1905.12153

Concrete Barriers to Quantifier Elimination in Finite-Dimensional C*-algebras

Christopher J. Eagle·Todd Schmid

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Abstract

Work of Eagle, Farah, Goldbring, Kirchberg, and Vignati shows that the only separable C*-algebras that admit quantifier elimination in continuous logic are $\mathbb{C},$ $\mathbb{C}^2,$ $M_2(\mathbb{C}),$ and the continuous functions on the Cantor set. We show that, among finite dimensional C*-algebras, quantifier elimination does hold if the language is expanded to include two new predicate symbols: One for minimal projections, and one for pairs of unitarily conjugate projections. Both of these predicates are definable, but not quantifier-free definable, in the usual language of C*-algebras. We also show that adding just the predicate for minimal projections is sufficient in the case of full matrix algebras, but that in general both new predicate symbols are required.

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BibTeX RIS

Christopher J. Eagle, Todd Schmid. 2019-05-29. Concrete Barriers to Quantifier Elimination in Finite-Dimensional C*-algebras. https://arxiv.org/abs/1905.12153

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