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Finite group extensions of shifts of finite type:
$K$-theory, Parry and Livšic
Published online by Cambridge University Press: 11 February 2016
Abstract
This paper extends and applies algebraic invariants and constructions for mixing finite group extensions of shifts of finite type. For a finite abelian group $G$, Parry showed how to define a
$G$-extension
$S_{A}$ from a square matrix over
$\mathbb{Z}_{+}G$, and classified the extensions up to topological conjugacy by the strong shift equivalence class of
$A$ over
$\mathbb{Z}_{+}G$. Parry asked, in this case, if the dynamical zeta function
$\det (I-tA)^{-1}$ (which captures the ‘periodic data’ of the extension) would classify the extensions by
$G$ of a fixed mixing shift of finite type up to a finite number of topological conjugacy classes. When the algebraic
$\text{K}$-theory group
$\text{NK}_{1}(\mathbb{Z}G)$ is non-trivial (e.g. for
$G=\mathbb{Z}/n$ with
$n$ not square-free) and the mixing shift of finite type is not just a fixed point, we show that the dynamical zeta function for any such extension is consistent with an infinite number of topological conjugacy classes. Independent of
$\text{NK}_{1}(\mathbb{Z}G)$, for every non-trivial abelian
$G$ we show that there exists a shift of finite type with an infinite family of mixing non-conjugate
$G$ extensions with the same dynamical zeta function. We define computable complete invariants for the periodic data of the extension for
$G$ (not necessarily abelian), and extend all the above results to the non-abelian case. There is other work on basic invariants. The constructions require the ‘positive
$K$-theory’ setting for positive equivalence of matrices over
$\mathbb{Z}G[t]$.
- Type
- Research Article
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- Copyright
- © Cambridge University Press, 2016
References
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