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Lie Groups are Groups that are additionally smooth manifolds such that the multiplication and the inverse maps are smooth.

7 votes
Accepted

sub-tori of a torus, generated by 1-dimensional subgroup

The key to solving both problems is the use of the following two facts: 1) Any closed subgroup of $T^n$ is the intersection of the kernels of characters of $T^n$, i.e., continuous group homomorphisms …
Torsten Ekedahl's user avatar
15 votes
Accepted

Is a polynomial group law on $\mathbb{R}^n$ automatically nilpotent?

This is true and is in "Michel Lazard: Sur la nilpotence de certains groupes algébriques, Comptes Rendus, vol 241, 1955, 1687--1689"
Torsten Ekedahl's user avatar
34 votes
Accepted

Which groups have only real and quaternionic irreducible representations?

An irreducible representation is real or quaternionic precisely when its character is real-valued. By the Peter-Weyl theorem all characters are real-valued precisely when every element in the group is …
Torsten Ekedahl's user avatar
12 votes

Torsion for Lie algebras and Lie groups

I don't know the answer to the actual question but here is a situation which should be similar but simpler. Consider an integral polynomial group law $G$, i.e., a group scheme structure on the affine …
Torsten Ekedahl's user avatar