From: metroplex021 on
A while ago I heard the following two facts about semi-simple Lie
groups (though I have a feeling they may have to be restricted to
connected semi-simple Lie groups):

1. That semi-simple Lie groups are classified by their weight (and co-
weight) and root (and co-root) lattices;
2. That all of these lattices can be deduced from the fundamental
representations of the group. (So that if we have a complete set of
representations we can go on and infer the group.)

Can someone confirm for me that these are indeed the case, or suggest
a reference where the above are stated? (I am a physics graduate but
with little pure math knowledge, so the more approachable the
better.) Thanks a lot!
From: Timothy Murphy on
metroplex021 wrote:

> A while ago I heard the following two facts about semi-simple Lie
> groups (though I have a feeling they may have to be restricted to
> connected semi-simple Lie groups):
>
> 1. That semi-simple Lie groups are classified by their weight (and co-
> weight) and root (and co-root) lattices;
> 2. That all of these lattices can be deduced from the fundamental
> representations of the group. (So that if we have a complete set of
> representations we can go on and infer the group.)
>
> Can someone confirm for me that these are indeed the case, or suggest
> a reference where the above are stated? (I am a physics graduate but
> with little pure math knowledge, so the more approachable the
> better.) Thanks a lot!

I think Lie groups are normally assumed to be connected.

Adams, "Lectures on Lie Groups", is a very nice book on the subject.
It deals almost entirely with semisimple Lie groups.

(I don't think the associated book by Adams on Exceptional Lie Groups
is nearly so good; I believe it was completed by a student of Adams
after Adams' tragic early death.)

--
Timothy Murphy
e-mail: gayleard /at/ eircom.net
tel: +353-86-2336090, +353-1-2842366
s-mail: School of Mathematics, Trinity College, Dublin 2, Ireland