Cartesian Product of Permutations?

In summary, the conversation discussed the concept of a Cartesian product of groups and how it relates to the quotient group. The example used was the groups G = S3 and H = A3, where it was shown that G/H is isomorphic to the two element group {1,-1}. A general element of A3 x (S3/A3) was also given as (\sigma, \pm 1) where sigma is any even permutation. The conversation concluded with an example of multiplication within this group.
  • #1
Parmenides
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Suppose I was asked if [itex] G \cong H \times G/H [/itex]. At first I considered a familiar group, [itex]G = S_3 [/itex] with its subgroup [itex]H = A_3 [/itex]. I know that the quotient group is the cosets of [itex]H[/itex], but then I realized that I have no idea how to interpret a Cartesian product of any type of set with elements that aren't just numbers. An ordered pair of permutations doesn't make sense (this is not a homework question). I'd be grateful for some clarity.
 
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  • #2
If G1 and G2 are groups, then
[tex] G_1 \times G_2 = \{ (g_1,g_2)\ :\ g_1 \in G_1,\ g_2\in G_2 \} [/tex]
with the multiplication
[tex] (g_1,g_2)\cdot (h_1,h_2) = (g_1 h_1, g_2 h_2) [/tex].

So if you have G = S3, and H = A3, G/H is isomorphic to the two element group {1,-1} (where each permutation gets mapped to its parity), and a general element of A3 x (S3/A3) is [itex] (\sigma, \pm 1 ) [/itex] where sigma here is any even permutation.

For example,
[tex] \left( (1 2 3 ),-1 \right) \cdot \left( (1 2 3), 1 \right) = \left( (1 3 2), -1 \right) [/tex]
is a multiplication inside of this group.
 

Related to Cartesian Product of Permutations?

1. What is the definition of Cartesian Product of Permutations?

The Cartesian Product of Permutations is a mathematical operation that combines two or more permutations to create a new set of ordered pairs. It is denoted by the symbol "×" and can be thought of as taking all possible combinations of elements from the two permutations.

2. How is the Cartesian Product of Permutations calculated?

To calculate the Cartesian Product of Permutations, you multiply the number of elements in each permutation. For example, if the first permutation has 3 elements and the second permutation has 4 elements, the Cartesian Product will have 3 × 4 = 12 elements.

3. What is the difference between Cartesian Product and Cross Product?

Cartesian Product and Cross Product are both mathematical operations that combine two sets of elements. However, Cartesian Product is used for permutations, where order matters, while Cross Product is used for combinations, where order does not matter.

4. What are some real-life applications of Cartesian Product of Permutations?

The Cartesian Product of Permutations has many applications in computer science, such as generating all possible combinations for a password or creating test cases for software testing. It is also used in statistics and probability to calculate the number of possible outcomes in a given scenario.

5. Is the Cartesian Product of Permutations commutative?

No, the Cartesian Product of Permutations is not commutative. This means that the order in which the permutations are multiplied matters. In other words, P × Q is not always equal to Q × P. This is because the resulting set of ordered pairs will be different depending on the order of the permutations.

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