From: metroplex021 on
Hi folks - I have a couple of basic questions about fundamental
representations.

First of all, does every group have a set of fundamental
representations, or just the semi-simple groups?

Secondly, I know that in the case of the (compact?) semi-simple
groups, any other
representation of the group can be constructed by taking tensor
products of its L fundamental representations, where L is the group's
rank. Is this the case for all groups, or just the semi-simple ones?

Any help would be really appreciated. Thanks!
From: Maarten Bergvelt on
On 2010-06-15, metroplex021 <fourthinternational(a)googlemail.com> wrote:
> Hi folks - I have a couple of basic questions about fundamental
> representations.
>
> First of all, does every group have a set of fundamental
> representations, or just the semi-simple groups?

What do you mean by fundamental representation of a group. For
instance, a finite group has (over the complex numbers, say) n
irreducible representations, where n is the number of conjugacy
classes. Would you count them as fundamental? Every (finite dim) reps
will be a sum of irreducibles.

But if you take other groups it might not longer be true that any reps
is a sum of irreps, for instnce solvable groups. So what do you take
as fundamental reps?

> Secondly, I know that in the case of the (compact?) semi-simple
> groups, any other
> representation of the group can be constructed by taking tensor
> products of its L fundamental representations, where L is the group's
> rank. Is this the case for all groups, or just the semi-simple ones?



--
Maarten Bergvelt