Proving Abelian Factor Groups: Group Theory Homework Solution

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In summary, an Abelian factor group is a subgroup of a larger group where the elements commute with each other. To prove that a factor group is Abelian, one must show that the elements in the subgroup commute with each other. This is significant because it simplifies the group and has useful properties. Common methods for proving Abelian factor groups include using the definition of Abelian groups, properties of cosets and normal subgroups, and the quotient group theorem. Not all factor groups are Abelian, as the elements must commute for the group to be Abelian.
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Benzoate
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Homework Statement


PRove that a factor group of an abelian group is abelian

Homework Equations


The Attempt at a Solution



Assume G in G/H is abelian. Let there be elements a and b that are in G. such that ab=ba. Since H is a subgroup of G , elements a and b are also in H. Then (aH)(bH)=ab(H) =ba(H)=(bH)(aH) . Therefore , factor group G/H is abelian.

Is my proof correct?
 
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  • #2
G in G/H is abelian? How about 'G is abelian'. Let there be elements in a and b that are in G such that ab=ba? How about 'Since G is abelian any arbitrary choice of a and b in G will commute'. Since H is a subgroup of G, elements a and b are also in H? There is no injection between G and H unless G=H (H is a subset of G). What you want to say is that every element a in G corresponds to an a+H in G/H.

You have the right idea though.
 
  • #3
Benzoate said:
Assume G in G/H is abelian.
What do you mean? G is abelian (given), G/H is abelian (trying to prove that). G is not in G/H

Benzoate said:
Let there be elements a and b that are in G. such that ab=ba.
ab = ba is automatically true if a and b are in G, yes.

Benzoate said:
Since H is a subgroup of G , elements a and b are also in H.
If and only if G = H of course, then G/H = {1} which is abelian. So the statement is false, but do you need it?

Benzoate said:
Then (aH)(bH)=ab(H) =ba(H)=(bH)(aH) . Therefore , factor group G/H is abelian.
This looks like the key line in the proof. It's ok, just check what assumptions you need, reviewing the lines above.
 

FAQ: Proving Abelian Factor Groups: Group Theory Homework Solution

What is an Abelian factor group?

An Abelian factor group is a subgroup of a larger group that is also Abelian, meaning that its elements commute with each other. This means that the order in which the elements are multiplied does not affect the result.

How do you prove that a factor group is Abelian?

To prove that a factor group is Abelian, one must show that the elements in the subgroup commute with each other. This can be done by showing that for any two elements a and b in the subgroup, ab = ba.

What is the significance of proving that a factor group is Abelian?

Proving that a factor group is Abelian is significant because it allows us to simplify the group and make it easier to work with. Additionally, Abelian groups have many useful properties and can be used in various applications in mathematics and science.

What are some common methods for proving Abelian factor groups?

Some common methods for proving Abelian factor groups include using the definition of Abelian groups and verifying that the elements in the subgroup commute, using the properties of cosets and normal subgroups, and using the quotient group theorem.

Are all factor groups Abelian?

No, not all factor groups are Abelian. In order for a factor group to be Abelian, the elements in the subgroup must commute with each other. If this condition is not met, then the factor group will not be Abelian.

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