I keep hearing statements like "XXX theory is based on U(1)" or some such, but I haven't heard what this group actually is. If U(N) are the NxN unitary matrices, then U(1) are the 1x1 matrices such that x*=x^-1. So, I just want to confirm then, that U(1) is simply the 1 parameter Abelian Lie group given by [itex]e^{i\theta}[/itex]? This is simply the unit circle right, and should be isomorphic to rotations about a unit circle?(adsbygoogle = window.adsbygoogle || []).push({});

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# What is this U(1)?

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