# Power of a cycle

1. Nov 16, 2011

### Bachelier

let π be a product of disjoint m-cycles. Prove that π is a power of a cycle?

So this is like asking show that π = βx for some cycle β and pos. integer x. right?

I don't know how to proceed on this except for the fact that the order of π is m.

2. Nov 16, 2011

### mathwonk

what have you tried? remember, when you have no clue what will work, any idea at all is progress.

3. Nov 16, 2011

### Bachelier

man I have no idea.

I know I can write π = (....)(....)(....)(....)(....)(....)(....)(....)(....)(....)

probably need to consider when m is even and odd.

I can break down π to a product of transpositions.

But the end result is too abstract I can get my head around it.

4. Nov 17, 2011

### micromass

First, note that

$$\sigma (i_1~i_2~i_3~...~i_n) \sigma^{-1}=(\sigma(i_1)~\sigma(i_2)~\sigma(i_3)~...~\sigma(i_n))$$

This allows you to bring everything back to the cycle (1 2 3 ... n).

Now, take powers of (1 2 3 ... n) and see what types of disjoint cycle decompostions you meet.

5. Nov 22, 2011

### Bachelier

let ∏= ∏αi for all 1≤i≤n with αi = (ai1 ai2 ai3 ...aim)

consider θ = (a11 a21......an1 a12 a22......a1m a2m a3m...anm)

then applying θ n times will give us the original ∏.

Hence ∏ = θn