Determine if a group is cyclic

In summary, the question is whether a cyclic group of order 20 can have three or two elements of order 4. The necessary condition is that the powers of the elements must divide 20. However, this is not a sufficient condition as shown by considering the cyclic group of order 20 with the fourth power of each element expressed as ##g^m##, where ##m<20##.
  • #1
DeldotB
117
7
Hello all!

If I have a group of order 20 that has three elements of order 4, can this group be cyclic? What if it has two elements? I am new to abstract algebra, so please keep that in mind!

Thanks!
 
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  • #2
If it's cyclic then it has a generator element g such that ##g^{20}=1## and ##1,g,g^2,...,g^{19}## are all different.

Let the three elements of order 4 be a, b and c.

What can we deduce about what powers of g each of those elements could be?
 
  • #3
Do the powers need to divide 20?
 
  • #4
That's a sufficient, but not a necessary condition.

Think about the* cyclic group of order 20: {1,##g,g^2,...,g^{19}##}. Express the fourth power of each of its elements as ##g^m## where ##m<20##.

*Note the use of 'the' rather than 'a'. All cyclic groups of order 'n' are isomorphic.
 

Related to Determine if a group is cyclic

1. What is a cyclic group?

A cyclic group is a mathematical object that is formed by a set of elements and a binary operation that combines two elements to produce a third element. The elements in a cyclic group are generated by repeatedly applying the binary operation to a starting element, known as the generator.

2. How can you determine if a group is cyclic?

A group is considered cyclic if there exists a single element, known as the generator, that can generate all the other elements in the group by repeatedly applying the group operation. In other words, if every element in the group can be expressed as a power of the generator, then the group is cyclic.

3. What are the properties of a cyclic group?

One of the main properties of a cyclic group is that it is abelian, meaning that the group operation is commutative. Additionally, every cyclic group is finite and has a finite number of elements. Lastly, every subgroup of a cyclic group is also cyclic.

4. Can a non-abelian group be cyclic?

No, a non-abelian group cannot be cyclic. This is because the defining property of a cyclic group is that it is abelian, and a non-abelian group, by definition, does not satisfy this property.

5. What is the significance of cyclic groups in mathematics?

Cyclic groups play a crucial role in many areas of mathematics, including number theory, abstract algebra, and group theory. They also have applications in cryptography and coding theory. Additionally, cyclic groups are used to study other mathematical objects, such as fields and vector spaces.

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