Subfields of Ample Fields I. Rational Maps and Definability
نویسنده
چکیده
Pop proved that a smooth curve C over an ample field K with C(K) 6= ∅ has |K| many rational points. We strengthen this result by showing that there are |K| many rational points that do not lie in a given proper subfield, even after applying a rational map. As a consequence we gain insight into the structure of existentially definable subsets of ample fields. In particular, we prove that a perfect ample field has no existentially definable proper infinite subfields.
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