How to Calculate Permutation Powers with Functional Notation?

  • Context: Undergrad 
  • Thread starter Thread starter vivaitalia1
  • Start date Start date
  • Tags Tags
    Permutations
Click For Summary

Discussion Overview

The discussion revolves around calculating the power of a permutation, specifically how to express the permutation \( p \) raised to the power of 100 using functional notation. The context includes theoretical aspects of permutations and their representation in different notations.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Homework-related

Main Points Raised

  • One participant expresses confusion about how to calculate \( p^{100} \) and seeks guidance on the process.
  • Another participant suggests decomposing the permutation into disjoint cycles and provides the decomposition as \( p = (1, 3, 7)(2, 5)(4, 6, 9, 8, 10) \).
  • It is noted that the orders of the cycles affect the calculation of \( p^{100} \), with two cycles resulting in the identity and the remaining cycle being raised to the power of 100.
  • A participant questions whether the task involves running the permutation through 100 cycles.
  • Clarification is provided that the question is about raising the disjoint cycles to the power of 100, not running through cycles.
  • One participant asks for clarification on what is meant by 'functional notation' and whether it refers to the disjoint cycle notation.
  • Another participant suggests that functional notation may refer to a matrix-like representation of permutations.
  • A later reply raises the issue of differing conventions in multiplying permutations, noting that some textbooks may use left-to-right or right-to-left multiplication, which could lead to confusion.

Areas of Agreement / Disagreement

Participants generally agree on the method of calculating the power of the permutation through disjoint cycles, but there is uncertainty regarding the interpretation of 'functional notation' and the conventions used in different textbooks.

Contextual Notes

There is a lack of consensus on the definition of functional notation and how it relates to the disjoint cycle notation. Additionally, the discussion highlights potential confusion arising from different conventions in permutation multiplication.

vivaitalia1
Messages
5
Reaction score
0
I might be a bit thick in this but i just can't figure out how to answers this exam question:

Calculate p to the power of 100, writing your answer in functional notation

p is the permutation(n=10): (3,5,7,6,2,9,1,10,8,4). It should say 1-10 on the top but i don't know how to draw matrices here.

Anyways, point is, how do you do these kinds of questions? :(
 
Physics news on Phys.org
Decompose it into a product of disjoint cycles. In this case you'll find p = (1, 3, 7)(2, 5)(4, 6, 9, 8, 10).

The second cycle up there has order 2 and the last has order 5, so p^{100} = (1, 3, 7)^{100}.

Notice that (1, 3, 7)^2 = (1, 7, 3) and (1, 7, 3)^2 = (1, 3, 7). That should be enough for you to work it out. :smile:
 
So is the question infact asking me to run the permutation through 100 cycles?
 
No, the question is asking yo to raise dsjoint 3, 2 and 5 cycles to the power 100. Clearly two of those 2 disjoint cycles raised to the power 100 are the identity, and the remaining on is just that cycle again. You understand that if a group element, g, has order n, then g^m is the same as g^r where r=m mod n, right?
 
Yes i know that. thanks a lot for the explanation :)

Just one last thing.. what's 'functional notation'? is it the disjoint cycles notation? so basically my answer would be the same as the dijoint cycle notation for this permutation?

i missed soo many lectures (im studying comp science) and basicalyl I am teaching myself the whole syllabus
 
Functional notation probably means the type that you tried to use in your first post (the type that looks sort of like a matrix).
 
vivaitalia1, another thing you might think about is whether the author of your textbook is multiplying permutations left to right or right to left. Unfortunately, modern algebra books seem to be divided about fifty-fifty. (One author, Herstein, even wrote a classic modern algebra textbook using one convention and then wrote a second modern algebra textbook using the other convention!) This can cause great confusion to unwary but diligent students who are comparing treatments in different books! (Otherwise a smart thing to do.)
 
Last edited:

Similar threads

  • · Replies 13 ·
Replies
13
Views
2K
  • · Replies 6 ·
Replies
6
Views
8K
Replies
1
Views
2K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 7 ·
Replies
7
Views
3K
  • · Replies 3 ·
Replies
3
Views
4K
  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K