7 papers
Existential fragments of theories of henselian valued fields
Sylvy Anscombe, Arno Fehm
We study fragments of the existential theory of henselian valued fields with parameters. This includes the -fragment in the equicharacteristic or unramified mixed charac…
Elimination results for tame fields with finite residue fields
Sylvy Anscombe, Blaise Boissonneau
Building on work of Kuhlmann and Lisinski, we study the theory of the Hahn series field , over a finite field , equipped with the…
A note on existentially t-henselian fields
Sylvy Anscombe
A field is existentially t-henselian if it is has the same existential theory in the first-order language of rings as a field that admits a nontrivial henselian valuation. This pro…
The model theory of perfectoid fields [after Jahnke and Kartas]
Sylvy Anscombe
This text was written to support a Bourbaki seminar given in January 2026 on the subject of the model theory of perfectoid fields, especially on the work of Jahnke and Kartas in th…
Ax-Kochen-Ershov principles for finitely ramified henselian fields
Sylvy Anscombe, Philip Dittmann, Franziska Jahnke
We study the model theory of finitely ramified henselian valued fields of fixed initial ramification, obtaining versions of the Ax-Kochen-Ershov principle as follows. We identify t…
Universal-existential theories of fields
Sylvy Anscombe, Arno Fehm
We study various universal-existential fragments of first-order theories of fields, in particular of function fields and of equicharacteristic henselian valued fields. For example…