Conjugacy Classes of n-cycles in An and Their Elements

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SUMMARY

The discussion centers on the conjugacy classes of n-cycles in the alternating group An, specifically when n is odd. It is established that there are exactly two conjugacy classes of n-cycles in An, each containing (n-1)!/2 elements. The participants clarify that An contains every n-cycle as these are even permutations, and the total number of n-cycles is (n-1)!. The conversation highlights confusion regarding terminology such as "CCl" and the notation (12)x(12), indicating a need for further explanation on these concepts.

PREREQUISITES
  • Understanding of group theory concepts, particularly alternating groups.
  • Familiarity with conjugacy classes in group theory.
  • Knowledge of permutations and cycle notation.
  • Basic grasp of even and odd permutations in symmetric groups.
NEXT STEPS
  • Study the properties of alternating groups, specifically An.
  • Learn about the calculation of conjugacy classes in symmetric and alternating groups.
  • Explore the concept of stabilizers and orbits in group actions.
  • Investigate the implications of odd and even permutations in group theory.
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Mathematicians, particularly those specializing in group theory, students studying algebra, and anyone interested in the properties of permutations within alternating groups.

pandasong
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(Moderator's note: thread moved from "Set Theory, Logic, Probability, Statistics")

the question is
if n is odd then there are exactly two conjugacy classes of n cycles in An each of which contains (n-1)!/2 elements.
also there is a hint says let An act on itself
i know the fact that since An acts on itself, x doesn't commute with any odd permutation. So it splits into two Ccl An (x) and CCl An (12)x(12).
But i can't figure it out how to calculate either the number of stabilizers or the number of orbits
 
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Your question is rather difficult to understand. eg. what do you mean by "CCl", "Ccl", (12)x(12)? And what is x?

I don't even think this is true! eg: in A3, the two 3-cycles: (123) and (132) commute, and so they are in the same conjugacy class.

For what it's worth, it might help you to note that if n is odd, then An contains every n-cycle, as these are even permutations. Also that the number of these n-cycles is: (n-1)! (as we can fix the 1 at the beginning of the cycle and then permute the other (n-1) numbers in every possible way).

Otherwise you will need to explain more.
 
mrbohn1 said:
Your question is rather difficult to understand. eg. what do you mean by "CCl", "Ccl", (12)x(12)? And what is x?

I don't even think this is true! eg: in A3, the two 3-cycles: (123) and (132) commute, and so they are in the same conjugacy class.

For what it's worth, it might help you to note that if n is odd, then An contains every n-cycle, as these are even permutations. Also that the number of these n-cycles is: (n-1)! (as we can fix the 1 at the beginning of the cycle and then permute the other (n-1) numbers in every possible way).

Otherwise you will need to explain more.
well the permutations you gave they are in ccl An
its what is written on my lecture notes actually i also don't know much about it but it has the same conj. class with ccl an
 

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