Can an Abelian Group Be Isomorphic to a Non-Abelian Group in Physics?

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Discussion Overview

The discussion revolves around the question of whether an abelian group can be isomorphic to a non-abelian group, exploring concepts from group theory and their implications in the context of molecular symmetry groups and point groups.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant questions if an abelian group can be isomorphic to a non-abelian group.
  • Another participant argues that the defining property of non-abelian groups, where the order of multiplication affects the outcome, prevents isomorphism with abelian groups.
  • A later reply references an article suggesting that the molecular symmetry group, which is typically non-abelian, is isomorphic to its point group, which is generally abelian, raising questions about the validity of this claim.
  • Another participant corrects the previous assertion about point groups, stating that most point groups are not abelian, using the cubic group as an example.
  • A participant acknowledges the correction regarding point groups.
  • Further questions arise about constructing the character table of irreducible representations based on the multiplication table of groups.

Areas of Agreement / Disagreement

Participants express disagreement regarding the properties of point groups and their relationship to abelian and non-abelian groups, with no consensus reached on the original question of isomorphism.

Contextual Notes

There are unresolved assumptions regarding the definitions of groups and the specific contexts in which the properties of abelian and non-abelian groups are applied.

Konte
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Hi everybody,

I have a question: is an abelian group can be isomorphic to a non-abelian group?

Thank you everybody.
 
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In a non-abelian group, there are at least two elements A and B so that A*B=C but B*A=D with different D and C. this is not possible in an abelian group, so the two groups can also not be isomorphic.
 
DrDu said:
In a non-abelian group, there are at least two elements A and B so that A*B=C but B*A=D with different D and C. this is not possible in an abelian group, so the two groups can also not be isomorphic.

I thought so. But I asked this question because I have read this article of G.Bone and Co. http://dx.doi.org/10.1080/00268979100100021(in appendix page 71-72), which states that the Molecular symmetry group (MS) of a rigid molecule is isomorphic to its point group. Knowing that the MS group is composed of nuclear permutation-inversion operation, I verified by myself this group is in general non-abelian, and on the other side, point group are in general abelian. So, did they say something wrong?

Thank you.

Konte
 
Most point groups aren't abelian. Take a cubic group, like Oh as an example: Rotate first 90 deg, around x and then 90 deg. around y. Compare to first rotating 90 deg around y and then 90 deg around x.
 
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Likes   Reactions: Konte
You are right, I missed it.
Thanks a lot.

I have another question, how to construct the character table of irreducible representation knowing the multiplication table of the group?
 
This can be arbitrarily nontrivial. Best have a look on a decent book on group theory. As you are mainly interested in the symmetric group, Sternberg, "Group theory and physics" might be what you are looking for.
 
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Likes   Reactions: Konte
Ok. Thanks!
 

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