Rational pullbacks of Galois covers
Research output: Contribution to journal › Research article › Contributed › peer-review
Contributors
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
Original language | English |
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Pages (from-to) | 1507-1531 |
Number of pages | 25 |
Journal | Mathematische Zeitschrift |
Volume | 299 |
Issue number | 3-4 |
Publication status | Published - Dec 2021 |
Peer-reviewed | Yes |
Keywords
ASJC Scopus subject areas
Keywords
- Galois covers, Inverse Galois theory, Rational pullback