How Do You Decompose a Random n-Cycle into 2-Cycles?

In summary, a permutation cycle is a way of representing the rearrangement of objects in a set. It is written in a specific format with elements separated by a space and enclosed in parentheses. The order of a cycle is the number of elements in the cycle, and cycles can overlap. The parity of a cycle is determined by the number of cycles it takes to rearrange the elements, which is useful in determining the sign of a permutation.
  • #1
frb
16
0
can anyone explain me the technique to decompose a random n-cycle into a bucnh of 2 cycles. Thanks in advance.
 
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  • #2
Look at: (ab)(ac). Approaching this from the left, we have (1) a goes to b. (2) b goes to a in cycle one, and then a goes to c in cycle two. (3) As for c it is sent into a, cycle two.

Thus (abc)=(ab)(ac). And so forth, (abcd) = (ab)(ac)(ad), etc.
 
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  • #3


Permutation cycles are an important concept in mathematics and can be used to represent various operations and transformations. The technique to decompose a random n-cycle into a bunch of 2 cycles is known as cycle decomposition.

To understand this technique, let's first define what a permutation cycle is. A permutation cycle is a way of representing a permutation as a sequence of numbers, where each number is mapped to the next number in the sequence. For example, the permutation (1 2 3) can be represented as the cycle (1 2 3).

Now, to decompose a random n-cycle into a bunch of 2 cycles, we need to follow these steps:

1. Start with the first number in the n-cycle and write it in a cycle as (x1). This will be our first 2-cycle.

2. Next, find the number that is mapped to x1 in the n-cycle. Let's call this number x2. Write this number in the same cycle as (x1 x2).

3. Continue this process, finding the number that is mapped to the last number in the cycle and adding it to the cycle until we reach the first number again. This will give us a complete 2-cycle.

4. Now, we need to move on to the next number in the n-cycle that has not been included in any previous 2-cycle. Repeat the same process as above to create another 2-cycle.

5. Continue this process until we have included all the numbers from the n-cycle in 2-cycles.

By following these steps, we can decompose a random n-cycle into a bunch of 2-cycles. It is important to note that this decomposition is not unique, and there can be multiple ways to decompose a given n-cycle into 2-cycles.

I hope this explanation helps you understand the technique of cycle decomposition. If you have any further questions, please feel free to ask.
 

1. What is a permutation cycle?

A permutation cycle is a way of representing the rearrangement of objects in a set. It is a sequence of elements that are moved from their original positions to new positions. For example, if we have the set {1, 2, 3, 4} and we rearrange it to {2, 4, 3, 1}, the permutation cycle would be (1 2 4 3).

2. How do you write a permutation cycle?

Permutation cycles are written in a specific format, with the elements separated by a space and enclosed in parentheses. The first element represents the starting position of the object, and the following elements represent its new position after each rearrangement. For example, if we have the set {1, 2, 3, 4} and we rearrange it to {3, 4, 1, 2}, the permutation cycle would be (1 3 2 4).

3. What is the order of a permutation cycle?

The order of a permutation cycle is the number of elements in the cycle. For example, if we have a cycle (1 3 2 4), the order would be 4 because there are four elements in the cycle. The order of a permutation cycle can also be thought of as the number of times the cycle needs to be repeated to return the elements to their original positions.

4. Can permutation cycles overlap?

Yes, permutation cycles can overlap. This means that one element can be moved to multiple positions in a single cycle. For example, in the cycle (1 2 3 4), the element 1 is moved to position 2, then to position 3, and finally back to its original position 1. Overlapping cycles can also be written as a composition of multiple cycles, such as (1 2)(2 3)(3 4)(4 1).

5. How do you determine the parity of permutation cycles?

The parity of a permutation cycle is determined by the number of cycles it takes to rearrange the elements. If the number of cycles is even, the permutation cycle has an even parity, and if the number of cycles is odd, the permutation cycle has an odd parity. This can be useful in determining the sign of a permutation, which is important in certain mathematical applications.

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