1. ## Centralizers

I am a little confused as to the definition of a centralizer. Is it the set of elements in H such that gh=hg or that ghg^{-1}=h?

Thanks,

Paul

2. Not to worry, I figured out that they are the same thing,

Paul

3. I was going to reply yesterday.
I seems you have to use the fact if $\tau = (a_1,...,a_k)(b_1,b_2 .... )...$
Then, $\sigma \tau \sigma^{-1} = (\sigma (a_1),....,\sigma(a_k))(\sigma(b_1),....)$.