Invertible matrices. Or if you think a bit more generally, an invertible linear map.
Non invertible are excluded "because" otherwise it would not form a group (every element must have an inverse).
- Important Lie groups | 0, 693, 13
- Lie group | 198, 1k, 19
- Important mathematical groups | 0, 1k, 25
- Group | 0, 2k, 47
- Algebra | 0, 2k, 65
- Mathematics | 17, 10k, 239
- Ciro Santilli's Homepage | 238, 147k, 2k
- Special linear group | 18