Minus sign(s) in polarization comparing different real time propagation schemes #172
Description
Real-time propagation with yambo_rt, td-ip level, velocity gauge.
Polarization with
(i) dipoles "G-space v" (red), yambo_rt in velocity (correct)
(ii) dipoles "Covariant" (blue), yambo_rt in velocity (-1 resulting from definition of polarization)
(iii) dipoles "Covariant" (magenta), yambo_nl in velocity (-1 resulting from definition of polarization)
(magenta and blue are on top)
The current in output
(i) dipoles "G-space v" (red), yambo_rt in velocity (correct)
(ii) dipoles "Covariant" (blue), yambo_rt in velocity (correct and identical to previous one)
(iii) dipoles "Covariant" (magenta), yambo_nl in velocity (-1 resulting from definition of current in terms of DIP_v, see next point)
Image below finally shows that the current is identical in the two rt runs, since coupling with external field is in yambo_rt velocity gauge, e.g. using velocity dipoles which are always directly evaluated in "G-space"
