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An incomplete real tree with complete segments - MaRDI portal

An incomplete real tree with complete segments (Q6581286)

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scientific article; zbMATH DE number 7889333
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English
An incomplete real tree with complete segments
scientific article; zbMATH DE number 7889333

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    An incomplete real tree with complete segments (English)
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    30 July 2024
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    Let \(\Lambda\) be a dense subgroup of \((\mathbb{R}, +)\) and let \(\mathcal{T}\) be a \(\Lambda\)-tree. The real tree associated to \(\mathcal{T}\) is defined as \(\mathcal{T}^{\mathrm{sc}}=\bigcup_{s \in S} \overline{s}\), where \(S\) is the set of segments in \(\mathcal{T}\) and \(\overline{s}\) is the metric completion of \(s\) in \(\mathcal{T}\).\N\NIn this paper the authors give an example of a \(\mathbb{Q}\)-tree \(\mathcal{T}\), as defined in [\textit{G. W. Brumfiel}, Contemp. Math. 74, 51--75 (1988; Zbl 0662.32022)] for which \(\mathcal{T}^{\mathrm{sc}}\) is not a complete metric space. In particular they prove that if \(\mathbb{F}\) is the field of real Puiseux series with \(\mathbb{Q}\)-valuation, and \(\mathcal{T}_{\mathbb{F}}\) is its associated \(\mathbb{Q}\)-tree, then \(\mathcal{T}^{\mathrm{sc}}_{\mathbb{F}}\) is not metrically complete.
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    \(\Lambda\)-trees
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    completions
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    non-Archimedean ordered fields
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