how do i define a bijective map form SU(2) to U(1) where SU(2) is the special unitary 2x2 matrix and U(1) is the unitary 1x1 matrix?

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- May 15th 2011, 12:25 PMalexandrabel90Bijective Map from SU(2) to U(1)
how do i define a bijective map form SU(2) to U(1) where SU(2) is the special unitary 2x2 matrix and U(1) is the unitary 1x1 matrix?

- May 15th 2011, 12:56 PMTinyboss
U(1) consists of complex numbers which are the inverse of their conjugate.

An element of SU(2) has the form such that the determinant is 1.

Can you finish from there? - May 15th 2011, 01:01 PMalexandrabel90
Not really. I was thinking of the determinant map but the determinant of all elements in su(n) is 1.

Can i instead define it as a map from the matrix ( tt you defined, which is in su(n) ) to the first element a ?

Seems wrong to me though.. - May 15th 2011, 03:56 PMalexandrabel90
i was thinking, can i define it from

cos(a) -isin(a)

isin(a) cos(a) seen as a matrix

to

exp(ia) which is in U(1)