A generalisation of von Staudt's theorem on cross-ratios

Yatir Halevi, Itay Kaplan

Research output: Contribution to journalArticlepeer-review


A generalisation of von Staudt's theorem that every permutation of the projective line that preserves harmonic quadruples is a projective semilinear map is given. It is then concluded that any proper supergroup of permutations of the projective semilinear group over an algebraically closed field of transcendence degree at least 1 is 4-transitive.

Original languageAmerican English
Pages (from-to)601-612
Number of pages12
JournalMathematical Proceedings of the Cambridge Philosophical Society
Issue number3
StatePublished - 2020

Bibliographical note

Publisher Copyright:
Copyright © Cambridge Philosophical Society 2019.


  • 2010 Mathematics Subject Classification: 14N99 20B27 20E28


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