Write as a Product of Transpositions

In summary, the permutation P = (123)(45687) can be written as a product of transpositions as (12)(23)(45)(56)(68)(87). This is done by breaking down each cycle into pairs of numbers and writing them as separate transpositions, then combining them all together.
  • #1
flufles
10
0

Homework Statement


Write the permutation
P=
12345678
23156847

in cycle notation, and then write it as a product of transpositions


Homework Equations





The Attempt at a Solution


I got the cycle notation to be (123)(45687), but i am now not sure now to write it as a product of transpositions. My only really thought was just grouping the digits in twos but i don't think that is correct

Thank you
 
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  • #2
Welcome to PF, flufles! :smile:

Each cycle can be written as a product of transpositions.
The most common methods are:
(1 2 3 4) = (1 4)(1 3)(1 2)
and
(1 2 3 4) = (1 2)(2 3)(3 4).
See the pattern?
 
  • #3
thank you for the welcome,
i think i do
so (123) could be written as (12)(23) or (13)(12)
and (45687) written as (45)(56)(68)(87) or (47)(48)(46)(45)
and so would i just put these next to each other as (12)(23)(45)(56)(68)(87)

Thank you
 
  • #4
Yep! That's it! :smile:

And you're welcome.
 
  • #5
thank you very much =]
 

Related to Write as a Product of Transpositions

1. How do you write a permutation as a product of transpositions?

To write a permutation as a product of transpositions, you need to first break down the permutation into cycles. Each cycle will have a certain number of elements, and you will need one transposition for each element in the cycle. Start with the first element in the cycle and swap it with the element that is in the second position. Then, take the element that was in the second position and swap it with the element that is in the third position, and continue until you reach the end of the cycle. Repeat this process for each cycle until you have written the entire permutation as a product of transpositions.

2. Why is it useful to write a permutation as a product of transpositions?

Writing a permutation as a product of transpositions can be useful in various mathematical and scientific applications. It allows for a more efficient way to represent and manipulate permutations, making calculations and proofs simpler and easier to understand. Additionally, it can also reveal certain properties and patterns of the permutation that may not be immediately obvious from its original form.

3. Is there a specific order in which the transpositions should be written?

No, there is no specific order in which the transpositions should be written. However, it is important to note that the order in which the elements are transposed does matter. In other words, the product of transpositions is not commutative, meaning that changing the order of the transpositions will result in a different permutation.

4. Can any permutation be written as a product of transpositions?

Yes, any permutation can be written as a product of transpositions. This is known as the transposition decomposition theorem, which states that every permutation can be expressed as a product of transpositions in a unique way. This theorem is a fundamental concept in the field of group theory and is widely used in various mathematical and scientific fields.

5. Can I use a different type of cycle to write a permutation as a product of transpositions?

Yes, in addition to using cycles of length 2 (transpositions), you can also use cycles of any length to write a permutation as a product of transpositions. However, using cycles of length greater than 2 may result in a longer product of transpositions. Therefore, using cycles of length 2 is typically the most efficient method for writing permutations as products of transpositions.

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