- #1
Pietjuh
- 75
- 0
Hello, I'm working on a problem in topology. I'm supposed to find the number of connected components of the group of 2x2 invertible upper triangular matrices over R which i shall call B_2.
I've tried it a bit, but I don't know for sure if my approach (and answer) is correct.
Since any homeomorphism preserves connectivity, I consider the trivial homeomorphism of B_2 to \mathbf{R}^3.
Since the matrices have to be invertible the determinant is non-zero which means that for matrices (a b | 0 c), ac > 0 or ac < 0. But he piece with positive determinant splits in 2 non connected pieces, {(a,b,c) | a > 0 and c > 0} and {(a,b,c) | a < 0 and c < 0}. The same sort of thing holds for the piece with negative determinant.
Is it correct to assert from this that B_2 has 4 connected components?
I've tried it a bit, but I don't know for sure if my approach (and answer) is correct.
Since any homeomorphism preserves connectivity, I consider the trivial homeomorphism of B_2 to \mathbf{R}^3.
Since the matrices have to be invertible the determinant is non-zero which means that for matrices (a b | 0 c), ac > 0 or ac < 0. But he piece with positive determinant splits in 2 non connected pieces, {(a,b,c) | a > 0 and c > 0} and {(a,b,c) | a < 0 and c < 0}. The same sort of thing holds for the piece with negative determinant.
Is it correct to assert from this that B_2 has 4 connected components?
