| Attribution: |

## QuestionEdit

It is well known the existence of a T-Duality between the two Heterotic String Theories, Type HO String Theory and Type HE String Theory. Beyond the trivial point that both groups have the same dimension (496, which actually is a prerequisite), is there some other mathematical relation between them?

I am thinking in other groups whose dimension is a perfect number and that happen to be related to products of manifolds. with , and -I am told- with some variant of . It should be nice if all of these were justified by a common construction, but I am happy just with an answer to the case.

#### CommentsEdit

## AnswersEdit

### Answer 1Edit

The key here are the weight lattices bosonic representations $\Gamma$ of these gauge groups.

As I understand it, the weight lattice of is , whereas the weight lattice of ^ is . The first fact means that the weight lattice of is ,

Now, an identity, that , which actually allows this T-Duality. Now, this means that it is *this very identity* which allows the identity mentioned in the original post.

So, the answer to your question is "**Yes**", there *is* a group-theoretical fact, and that is that .