Source: /cirosantilli/unitary-group

= Unitary group
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= $U(n)$
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<Group (mathematics)> of the <unitary matrices>.

<complex number>[Complex] analogue of the <orthogonal group>.

One notable difference from the orthogonal group however is that the unitary group is connected "because" its determinant is not fixed to two disconnected values 1/-1, but rather goes around in a continuous <unit circle>. $U(1)$ \i[is] the unit circle.