Abstract
We generalize and unify various tools from the study of valued fields equipped with an automorphism to obtain a relative quantifier elimination result for such fields. Along the way we point how the techniques we employ relate to a classical result from tropical geometry. The quantifier elimination result we provide is then applied to the transseries field equipped with the automorphism which sends \(f(x)\) to \(f(x+1)\).
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Notes
The conjecture is indeed false.
That is, valued difference fields where \(\sigma (\gamma )>n\gamma \) for all \(n\) whenever \(\gamma >0\).
With \({\varvec{i}}=(0,1,0 \ldots ,0)\), the multi-index \((0,0,1,0,\ldots ,0)\) can not be written as \({\varvec{i}}+{\varvec{j}}\), and hence we do not claim \(\sigma (\gamma _1)<\sigma ^2(\gamma _1)\), which is not true in general.
See [2], section 2, for the definition of complexity.
Generic elements from [12] correspond to regular elements.
The first author would like to thank Koushik Pal for bringing up this point, which has been neglected in [1].
It is also possible to obtain these maps with additional assumptions. For example if the value difference group is flat as a \(\mathbb Z [\sigma ]\)-module then the field admits a cross section in an elementary extension.
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Durhan, S., Onay, G. Quantifier elimination for valued fields equipped with an automorphism. Sel. Math. New Ser. 21, 1177–1201 (2015). https://doi.org/10.1007/s00029-015-0183-0
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DOI: https://doi.org/10.1007/s00029-015-0183-0