Abstract
For a function field in one variable F/K and a discrete valuation v of K with perfect residue field k, we bound the number of discrete valuations on F extending v whose residue fields are non-ruled function fields in one variable over k. Assuming that K is relatively algebraically closed in F, we find that the number of non-ruled residually transcendental extensions of v to F is bounded by \({\mathfrak {g}}+1\) where \({\mathfrak {g}}\) is the genus of F/K. An application to sums of squares in function fields of curves over \({\mathbb {R}}(\!(t)\!)\) is outlined.
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This work was supported by the FWO Odysseus Programme (Project G0E6114N, Explicit Methods in Quadratic Form Theory), funded by the Fonds Wetenschappelijk Onderzoek—Vlaanderen, by ANID (proyecto FONDECYT 11150956) and by the Universidad de Santiago de Chile (USACH proyecto DICYT, Codigo 041933 G).
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Becher, K.J., Grimm, D. Nonsplit conics in the reduction of an arithmetic curve. Math. Z. 306, 12 (2024). https://doi.org/10.1007/s00209-023-03395-3
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DOI: https://doi.org/10.1007/s00209-023-03395-3
Keywords
- Valuation
- Residue field extension
- Function field in one variable
- Genus
- Ruled residue theorem
- Minimal arithmetic surface
- Reduction theory
- Sums of squares