lie groups are continuous groups.
Classical Lie group:
	1. group multiplication = matrix multiplication
	2. members:  S0(n), O(n), GL(n, Complex), GL(n, Real), SL(n, Complex), SL(n, Real), U(n), SU(n)

S0(2) = rotational symmetry of a circle.
U(1) = phase matrix.  Isomorphic to SO(2).
O(2) = reflections and rotations of a circle.

GL(1,C)=g(t,th)=e^(t+ith) 0<=th<2Pi, -infinity<t<infinity
GL(1,R)+ = T = 1-d translation group.
SO(1,1) Isomorphic to T.
SO(n) has n(n-1)/2 parameters, compact
SU(n) has n*n-1 parameters, compact
The group manifold of SU(2) is S3.