Computable presentations of linear orders

2026

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DOI 10.1093/logcom/exag052
Data confidence 70 medium
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Abstract

Abstract This article explores computable reducibility for presentations of computable linear orders. In particular, this paper investigates the degree structures $\mathbf{P}(\mathcal{L})$ consisting of the $c$-degrees of computable copies of a fixed linear order $\mathcal{L}$, where $\mathcal{L}$ is one of the following: $\omega \cdot k$, $\omega ^{2}$, $\omega +\omega ^{*}$, $\zeta $ or $\omega \cdot \eta $. The main objective is to identify structural differences between these posets, focusing on the existence of least degrees, minimal degrees, universal degrees, minimal covers and the possible number of such covers. Among the notable differences, the structure $\mathbf{P}(\zeta )$ contains degrees with a minimal cover that is not a strong minimal cover, a phenomenon that does not occur in $\mathbf{P}(\omega )$.