Can prime fields act two ways on the same abelian group?

In summary, the conversation discusses finding an abelian group V and a field F with two different actions, denoted as \cdot and \odot, such that V is an F-module. One possible solution is to take a vector space over a field with a non-trivial automorphism group and define r\odot \mu to be f(r)\cdot \mu for f\in \text{Aut}(F), f\neq \iota. The question is whether this is the only way or if a prime field cannot act in two different ways on a module. Examples are provided, such as direct versus semidirect products and the group ##D_{12}##, which has two different operations on its elements.
  • #1
imurme8
46
0
A problem asks to find an abelian group [itex]V[/itex] and a field [itex]F[/itex] such that there exist two different actions, call them [itex]\cdot[/itex] and [itex]\odot[/itex], of [itex]F[/itex] on [itex]V[/itex] such that [itex]V[/itex] is an [itex]F[/itex]-module.

A usual way to solve this is to take any vector space over a field with a non-trivial automorphism group, and define [itex]r\odot \mu[/itex] to be [itex]f(r)\cdot \mu[/itex] for [itex]f\in \text{Aut}(F), f\neq \iota[/itex].

My question is: is this essentially the only way? Given two different actions of [itex]F[/itex] on [itex]V[/itex], can we construct a non-trivial automorphism of [itex]F[/itex]?

Or, a weaker result: can we show that a prime field cannot act in two different ways on a module?
 
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  • #2
We always have the trivial operation: ##F.V \equiv 0##.
Another example are direct versus semidirect products. And if the automorphism group is large enough, we can have different conjugations.

And ##D_{12} \cong V_4 \ltimes \mathbb{Z}_3 \cong D_6 \times \mathbb{Z}_2## might provide an example as we have two copies of ##\mathbb{Z}_2## here with a different operation on the rest.
 

1. What are prime fields?

Prime fields are fields that have only two elements, 0 and 1, and follow the arithmetic rules of addition and multiplication. They are denoted by the symbol Fp, where p is a prime number.

2. Can prime fields act on abelian groups?

Yes, prime fields can act on abelian groups. In fact, an abelian group can be defined as a set with an operation that follows the same rules as addition in a prime field.

3. How can prime fields act on abelian groups?

Prime fields act on abelian groups through a binary operation of addition or multiplication, depending on the specific group and field. This operation follows the rules of commutativity, associativity, and identity.

4. Can prime fields act two ways on the same abelian group?

No, prime fields can only act one way on the same abelian group. This is because the binary operation must be well-defined and follow the rules of an abelian group, which only allow for one operation.

5. Are there any limitations to how prime fields can act on abelian groups?

Yes, there are limitations to how prime fields can act on abelian groups. For example, the order of the field and the order of the group must be compatible, and the operation must follow the rules of an abelian group. Additionally, the field must have a prime number of elements and the group must be abelian.

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