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Jun 23, 2023 at 1:03 comment added user488802 Sorry to trouble with a related question. Could I also conclude that the conjugacy class in $G$ to which $E$ belongs is unique because it is from the regular representation?
Jun 22, 2023 at 8:52 comment added user488802 I think I've got it. Thank you for your patience!
Jun 22, 2023 at 7:41 comment added Dave Benson Okay, let me express this in terms of character theory. Your condition implies that the trace of all non-identity elements of $E$ is zero. So the inner products of your character with all one dimrensional irreducibles are equal. So the number of copies of each is the same. It follows that all automorphisms of $E$ take this to an isomorphic representation. The isomorphism then gives the required element of the normaliser to effect this automorphism of $E$. I hope this helps.
Jun 22, 2023 at 4:23 comment added user488802 Because there are other reps (where not every nontrivial elt is conjugate to $e$) which don't give this $N/C$ structure.
Jun 22, 2023 at 4:18 comment added user488802 I suppose my question is: for the 2nd possibility, why this particular representation where all the nontrivial elts are conjugate to $e$ gives the $N/C$ structure?
Jun 22, 2023 at 0:01 comment added user488802 I seem to have grasped your answer, thank you! Just one question on the last sentence. I'm being stupid here. Why in the regular representation case, $N/C$ is the full automorphism group? And you mean $k/p$ copies of the regular reps, right? Thank you!
Jun 21, 2023 at 22:58 vote accept user488802
Jun 21, 2023 at 22:34 comment added user488802 Sorry about that...
Jun 21, 2023 at 22:33 comment added Dave Benson You also keep accepting and unaccepting my answer, which is a little annoying.
Jun 21, 2023 at 22:32 comment added user488802 Sorry I forgot to write "thank you for all your input".
Jun 21, 2023 at 22:09 vote accept user488802
Jun 21, 2023 at 22:27
Jun 21, 2023 at 20:46 history edited Dave Benson CC BY-SA 4.0
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Jun 21, 2023 at 13:15 history edited Dave Benson CC BY-SA 4.0
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Jun 21, 2023 at 11:06 history edited Dave Benson CC BY-SA 4.0
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Jun 21, 2023 at 9:19 vote accept user488802
Jun 21, 2023 at 22:05
Jun 21, 2023 at 9:11 history edited Dave Benson CC BY-SA 4.0
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Jun 21, 2023 at 8:54 history answered Dave Benson CC BY-SA 4.0