Cycle Decomposition of Permutations

FlickS
Messages
3
Reaction score
0

Homework Statement


Let α = (α1α2...αs) be a cycle, for positive integers α1α2...αs. Let π be any permutation that παπ-1 is the cycle (π(α1)πα2...π(αs)).

Homework Equations

The Attempt at a Solution


I started by choosing a specific α and π, and tried finding παπ-1 to give myself some idea of what to do but have had no luck. Suggestions would be welcomed.
 
Physics news on Phys.org
FlickS said:

Homework Statement


Let α = (α1α2...αs) be a cycle, for positive integers α1α2...αs. Let π be any permutation that παπ-1 is the cycle (π(α1)πα2...π(αs)).

Homework Equations

The Attempt at a Solution


I started by choosing a specific α and π, and tried finding παπ-1 to give myself some idea of what to do but have had no luck. Suggestions would be welcomed.

For example, work out what is ##\pi \alpha \pi^{-1}(\pi(\alpha_1))##?
 
I would get παπ−1(π(α1)) = πα(α1)) = πα2?
It gives me the next element in the cycle. So παπ−1 would be that cycle.
I'm still relatively confused.
 
FlickS said:
I would get παπ−1(π(α1)) = πα(α1)) = πα2?
It gives me the next element in the cycle. So παπ−1 would be that cycle.
I'm still relatively confused.

Let's set ##\sigma=\pi \alpha \pi^{-1}## for short. You've shown ##\sigma(\pi(\alpha_1))=\pi(\alpha_2)##. Generalizing that I'd say the cycle structure of ##\sigma## is ##(\pi(\alpha_1)\pi(\alpha_2)...)##. Still confused?
 
Dick said:
Let's set ##\sigma=\pi \alpha \pi^{-1}## for short. You've shown ##\sigma(\pi(\alpha_1))=\pi(\alpha_2)##. Generalizing that I'd say the cycle structure of ##\sigma## is ##(\pi(\alpha_1)\pi(\alpha_2)...)##. Still confused?
Okay, that definitely makes its more clear. Thanks so much!
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
Back
Top