arXiv subjects
Publications and source records attributed to Lothar Sebastian Krapp.
We investigate what henselian valuations on ordered fields are definable in the language of ordered rings. This leads towards a systematic study of the class of ordered fields which are dense in their real closure. Some results have connections to recent conjectures on definability of henselian valuations in strongly NIP fields. Moreover, we obtain a complete characterisation of strongly NIP almost real closed fields.
Let $F$ be an archimedean field, $G$ a divisible ordered abelian group and $h$ a group exponential on $G$. A triple $(F,G,h)$ is realised in a non-archimedean exponential field $(K,\exp)$ if the residue field of $K$ under the natural valuation is $F$ and the induced exponential group of $(K,\exp)$ is $(G,h)$. We give a full characterisation of all triples $(F,G,h)$ which can be realised in a model of real exponentiation in the following two cases: i) $G$ is countable. ii) $G$ is of cardinality $κ$ and $κ$-saturated for an uncountable regular cardinal $κ$ with $κ^{<κ} = κ$. Moreover, we show that for any o-minimal exponential field $(K, \exp)$ satisfying the differential equation $\exp' = \exp$, its residue exponential field is a model of real exponentiation.