Elementary cyclic normal group theory

In summary, the problem states that if G is a finite group and H is a normal subgroup of G with finite index m=[G:H], we need to show that a^m\in H for all a\in G. The solution involves considering the canonical map \phi : G \rightarrow G/H, which is defined by g \mapsto gH. We also need to use the fact that the order of a group is equal to the order of its elements, which is only true for cyclic groups and generators.
  • #1
eileen6a
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Homework Statement


If G is a finite group and let H be a normal subgroup of G with finite index m=[G:H]. Show that [itex]a^m\in H[/itex] for all a[itex]\in[/itex] G.


Homework Equations


order of a group equal the order of element.


The Attempt at a Solution


no idea.
 
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  • #2
Consider the canonical map [itex]\phi : G \rightarrow G/H[/itex] defined by [itex]g \mapsto gH[/itex]. What can you say about [itex]\phi(a^m)[/itex]?

P.S. "order of a group equal the order of element" is false unless the group is cyclic and the element is a generator of the group.
 

Related to Elementary cyclic normal group theory

What is an elementary cyclic normal group?

An elementary cyclic normal group is a type of group in abstract algebra that is both cyclic (meaning it can be generated by a single element) and normal (meaning its subgroups are also normal). It is a fundamental concept in group theory and can be found in various mathematical fields, such as number theory and geometry.

What are the properties of an elementary cyclic normal group?

An elementary cyclic normal group has the following properties:

  • It is cyclic, meaning it can be generated by a single element.
  • It is normal, meaning all of its subgroups are also normal.
  • It is abelian, meaning its group operation is commutative.
  • It has a unique subgroup of every order, which is also normal.
  • Its order (number of elements) is a power of a prime number.

How is an elementary cyclic normal group different from a cyclic group?

An elementary cyclic normal group is a special case of a cyclic group. While all elementary cyclic normal groups are cyclic, not all cyclic groups are elementary cyclic normal groups. The key difference is that an elementary cyclic normal group must also be normal, while a cyclic group does not necessarily have this property.

What is the significance of elementary cyclic normal groups?

Elementary cyclic normal groups are important in abstract algebra and other mathematical fields because they provide a simpler and more structured understanding of groups. They also have many useful properties and can be used to prove theorems and solve problems in various areas of mathematics.

Can an elementary cyclic normal group have non-abelian subgroups?

No, an elementary cyclic normal group cannot have non-abelian subgroups. This is because all of its subgroups are normal, and a non-abelian subgroup would not be normal in an abelian group. Additionally, an elementary cyclic normal group is itself abelian, so it cannot contain any non-abelian subgroups.

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