Not a specific problem, just some help with the one step subgroup test

In summary, the one step subgroup test is an important tool in determining if a subset of a group is a subgroup. It involves showing that if two elements are in the subset, then their inverse is also in the subset. A simple example of this is the integers with addition as the operation, where the subset of multiples of 3 is shown to be a subgroup using this test.
  • #1
bennyska
112
0

Homework Statement


i just don't really get the one step subgroup test, which is very important, and something i should understand. can someone walk me through in general how to use the test? maybe give me a simple example? thanks.


Homework Equations





The Attempt at a Solution

 
Physics news on Phys.org
  • #2
Here's a simple example. Let G be the integers with addition as the operation. Let H be the subset of G consisting of the multiples of 3. In G, the [additive] inverse of x is -x.

To show H is a subgroup by that test you must show that if x and y are in H, then x + (-y) is in H.

x in H says x = 3m for some m in G and y in H says y = 3n for some n in G. The inverse of y is then -3n so the expression x + (-y) is just

3m + (-3n) = 3(m + (-n)), using the usual rules. This is a multiple of 3 and therefore in H. So H is a subgroup.
 

FAQ: Not a specific problem, just some help with the one step subgroup test

What is the one step subgroup test?

The one step subgroup test is a method used in group theory to determine if a subset of a group is a subgroup. It involves checking if the subset is closed under the group operation and if it contains the identity element and inverses of all its elements.

How is the one step subgroup test performed?

The one step subgroup test is performed by first identifying the subset in question and then checking if it satisfies the three conditions: closure, identity, and inverses. If all three conditions are met, then the subset is a subgroup.

3. What is the importance of the one step subgroup test?

The one step subgroup test is important because it allows us to quickly determine if a subset of a group is a subgroup without having to go through the more tedious process of verifying all the properties of a subgroup. It also helps us understand the structure and properties of groups better.

4. Can the one step subgroup test be applied to all groups?

No, the one step subgroup test can only be applied to finite groups. For infinite groups, there are more complex methods for determining if a subset is a subgroup.

5. Are there any limitations to the one step subgroup test?

Yes, the one step subgroup test can only be used to determine if a subset is a subgroup, but it cannot tell us if the subset is a normal subgroup. To determine if a subset is a normal subgroup, we need to use other methods such as the index test or the conjugation test.

Similar threads

Replies
15
Views
2K
Replies
4
Views
3K
Replies
4
Views
2K
Replies
6
Views
2K
Replies
17
Views
3K
Replies
25
Views
3K
Replies
23
Views
3K
Replies
3
Views
3K
Back
Top