Let \(U\) be a connected Lie subgroup of \(\mathrm {GL}_n(\mathbb {R})\). Suppose that every element of \(U\) has all of its entries below the main diagonal equal to 0, and all of its entries on the main diagonal equal to 1. Why is \(U\) diffeomorphic to \(\mathbb {R}^k\) for some \(k\)?
Question
Math 6510 • Differentiable Manifolds
Fall 2010 • Question 6