Skip to main content
13 events
when toggle format what by license comment
Apr 19, 2022 at 19:26 history edited Sam Hopkins CC BY-SA 4.0
added 168 characters in body
Apr 19, 2022 at 19:25 comment added Dominic van der Zypen No worries Sam, I wasn't explicit in this question, and thanks for your question dealing explicitly with infinite graphs.
Apr 19, 2022 at 19:24 history edited Sam Hopkins CC BY-SA 4.0
added 19 characters in body
Apr 19, 2022 at 19:23 comment added Sam Hopkins @DominicvanderZypen: Apologies, I did not realize you were also asking about infinite graphs. At any rate, the other question I posted will hopefully resolve this remaining part.
Apr 19, 2022 at 19:22 comment added Dominic van der Zypen @bof 's comment shows that the question has only been answered for finite graphs -- but your answer, Sam, is so interesting that I decided to accept (and upvote)
Apr 19, 2022 at 19:16 vote accept Dominic van der Zypen
Apr 19, 2022 at 18:44 comment added Sam Hopkins @bof I asked this as a new question here: mathoverflow.net/questions/420668/….
Apr 19, 2022 at 16:14 comment added Sam Hopkins @AgnishomChattopadhyay: but that is about whether the group is abstractly the automorphism group of a graph, which then tells you nothing about fixed points.
Apr 19, 2022 at 16:12 comment added Agnishom Chattopadhyay According to mathoverflow.net/questions/37356/… : every (finite or infinite) group is the automorphism group of some graph Taking the fact given by Sam Hopkins and using the above link answers @bof 's question
Apr 19, 2022 at 12:37 comment added Sam Hopkins @GordonRoyle Of course, the identity is also not a derangement. (And yes it is very easy to find a transitive permutation action on an infinite set with no fixed-point free permutations: e.g. take all permutations which only displace finitely many things.)
Apr 19, 2022 at 10:38 comment added Gordon Royle There are infinite transitive permutation groups with no derangements other than the identity, but I don’t know if they can be the full automorphism group of a graph.
Apr 19, 2022 at 5:32 comment added bof Could there be a vertex-transitive infinite graph with no fixed-point-free automorphism?
Apr 18, 2022 at 20:13 history answered Sam Hopkins CC BY-SA 4.0