Constraining images of quadratic arboreal representations
| Autor: | Andrea Ferraguti, Carlo Pagano |
|---|---|
| Přispěvatelé: | Ferraguti, Andrea, Pagano, Carlo |
| Jazyk: | angličtina |
| Rok vydání: | 2020 |
| Předmět: |
Pure mathematics
Binary tree Conjecture Mathematics - Number Theory General Mathematics Local class field theory 010102 general mathematics Galois group Algebraic number field 01 natural sciences 010101 applied mathematics Number theory Quadratic equation FOS: Mathematics Number Theory (math.NT) Settore MAT/03 - Geometria 0101 mathematics Abelian group Mathematics |
| Zdroj: | International Mathematics Research Notices |
| Popis: | In this paper, we prove several results on finitely generated dynamical Galois groups attached to quadratic polynomials. First we show that, over global fields, quadratic post-critically finite polynomials are precisely those having an arboreal representation whose image is topologically finitely generated. To obtain this result, we also prove the quadratic case of Hindes' conjecture on dynamical non-isotriviality. Next, we give two applications of this result. On the one hand, we prove that quadratic polynomials over global fields with abelian dynamical Galois group are necessarily post-critically finite, and we combine our results with local class field theory to classify quadratic pairs over $\mathbb Q$ with abelian dynamical Galois group, improving on recent results of Andrews and Petsche. On the other hand we show that several infinite families of subgroups of the automorphism group of the infinite binary tree cannot appear as images of arboreal representations of quadratic polynomials over number fields, yielding unconditional evidence towards Jones' finite index conjecture. Sections 3 and 4 now swapped. Accepted for publication on IMRN |
| Databáze: | OpenAIRE |
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