Conjugacy Classes of n-cycles in An and Their Elements

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In summary, the question asks about the number of conjugacy classes of n-cycles in An if n is odd. The hint suggests using An acting on itself, but the calculation of stabilizers and orbits is still unclear. There is a discrepancy in the statement of the problem, as it may not be true in all cases. The provided example in A3 shows that some n-cycles may commute, leading to more than two conjugacy classes. Further clarification is needed to fully understand the problem.
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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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  • #2
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.
 
  • #3
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
 

1. What are conjugacy classes in an?

Conjugacy classes in an are a fundamental concept in group theory that describe the equivalence classes of elements within a group that are related by conjugation.

2. How do you determine the conjugacy classes in an?

To determine the conjugacy classes in an, you first need to identify the elements in the group that are related by conjugation. This can be done by multiplying each element in the group by a chosen element and then checking if the resulting element is the same as one of the original elements. The resulting elements that are the same are then grouped together to form a conjugacy class.

3. What is the significance of conjugacy classes in an?

Conjugacy classes in an help us understand the structure of a group and its subgroups. They also have important applications in areas such as number theory, physics, and cryptography.

4. Can two different groups have the same conjugacy classes?

Yes, it is possible for two different groups to have the same conjugacy classes. This is known as isoclassification and occurs when the groups have isomorphic subgroups.

5. How are conjugacy classes related to normal subgroups?

Conjugacy classes are closely related to normal subgroups. In fact, the conjugacy classes of a group are the cosets of its normal subgroups, and the number of conjugacy classes is equal to the index of the normal subgroup in the group.

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