Linear response spectrum in the rotating frame

[jdelpino]

Functions to retrieve the linear fluctuation spectrum in the lab frame already exist. Rotating frame spectrum can be useful to compare to e.g. lock-in amplifiers measurement

[jkosata]

This can be achieved via the Jacobian - a function stored in Result.jacobian which takes solutions and returns jacobian matrices
e.g. to get solution 1, branch 2, J = result.jacobian( result[1][2] )

The eigenvalues of J then give the fluctuation spectrum (which is very prone to misinterpretation).