Rational pullbacks of Galois covers
Publikation: Beitrag in Fachzeitschrift › Forschungsartikel › Beigetragen › Begutachtung
Beitragende
Abstract
The finite subgroups of PGL 2(C) are shown to be the only finite groups G with this property: for some integer r (depending on G), all Galois covers X→PC1 of group G can be obtained by pulling back those with at most r branch points along non-constant rational maps PC1→PC1. For G⊂ PGL 2(C) , it is in fact enough to pull back one well-chosen cover with at most 3 branch points. A consequence of the converse for inverse Galois theory is that, for G⊄ PGL 2(C) , letting the branch point number grow provides truly new Galois realizations F/ C(T) of G. Another application is that the “Beckmann–Black” property that “any two Galois covers of PC1 with the same group G are always pullbacks of another Galois cover of group G” only holds if G⊂ PGL 2(C).
Details
Originalsprache | Englisch |
---|---|
Seiten (von - bis) | 1507-1531 |
Seitenumfang | 25 |
Fachzeitschrift | Mathematische Zeitschrift |
Jahrgang | 299 |
Ausgabenummer | 3-4 |
Publikationsstatus | Veröffentlicht - Dez. 2021 |
Peer-Review-Status | Ja |
Schlagworte
ASJC Scopus Sachgebiete
Schlagwörter
- Galois covers, Inverse Galois theory, Rational pullback