geometry \(SO(2)\) and \(U(1)\) are isomorphic \(S^1\) is too, but not a group language \(SO(2)xSO(2)\) is the torus
\(SO(3) and U(2)\) are isomorphic \(S^*3*\) is too
h3 and page on algebraic curves (actually this is more analytic geometry, there’s already stuff in start of physics on that. maybe should be separate big page before topology and after abstract algebra?) + \(f(x, y) = 0\)