pauli matrices in yambo

[batman]

Dear Developers,

The sigma_y matrix defined in "yambo/src/modules/mod_D_lattice.F" is not correct. As Fortran in column major, reshaping [1,2,3,4] will give ([[1 3],[2 4]])
so the matrix is currently defined as -sigma_y(actual). I can see that in one of the Tait-Bryan angles (beta) defined in "yambo/src/setup/build_spin_sop.F" lacks minus sign. I guess the minus was removed to compensate this. When rotating spinors wave functions with time reversal symmetry, it picks up an additional phase of -1 (which does not effect the results due to gauge arbitrary ness). I also see some other instances where sigma_y is used. Is it a bug or was it intentionally coded in this way?

Best regards,
Murali

[Davide Sangalli]

I opened an issue: https://github.com/yambo-code/yambo/issues/50
Better to double check this.
I do not think it was coded like that on purpose.

Best,
D.