Find the conjugacy classes in .

Is there an easier way to do this than cutting out a square and checking every possibility?

Printable View

- April 19th 2009, 08:44 AMDeadstarConjugacy Classes
Find the conjugacy classes in .

Is there an easier way to do this than cutting out a square and checking every possibility? - April 19th 2009, 11:34 AMGammaslightly quicker
You know in general that every element of the center is in its own conjugacy class. When calculating orbits of group elements it is also useful to note you will not get anything new from anything in the centralizer of the element. Lastly, keep in mind that conjugacy classes is an equivalence relation, so hopefully those things can trim your work down a bit.

- April 20th 2009, 04:19 AMJaneBennet
Let be an element of order 4 in (i.e. a rotation).

Then so two of the conjugacy classes are

Now and are the only elements of of order 4. Since elements in the same conjugacy class have the same order, and since and don’t belong to the centre (and so don’t form their own singleton conjugacy classes), must be another conjugacy class.

This leaves you with just 4 elements (the reflections) to check.