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Conjugacy classes in the symmetric group are determined by the cycle type: the number of cycles of each length. So the conjugacy class in of permutations with one fixed point, one transposition, and one 3-cycle, contains elements: the support of the 3-cycle can be chosen in ways; there are two 3-cycles given the support; and the fixed point can be chosen from the remaining three points in 3 ways. This fixes the transposition. This is verified below.
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| (2) |
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You can use in to iterate through the members of a conjugacy class.
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In the following example you iterate through the members of , and pair them up with their inverses if they occur. In this case, every element is conjugate with its inverse, so all elements are paired up eventually and none are left over.
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Since the cycle type of a permutation on letters corresponds one-to-one with a partition , the number of different conjugacy classes is equal to the partition function at .
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Examining the conjugacy classes of the quaternion group, given by a Cayley table.
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| (11) |
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You see that there are two conjugacy classes of size one and three of size two.
There are only two groups of order less than with class number equal to . (In fact, of any finite order.)
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Verify the class numbers as follows:
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The class number of a direct product of groups can be computed if the class numbers of the individual factors are known.
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| (15) |