hi, today i learnt that if the mass in schrodinger equation is not a constant, then schrodinger equation is not valid. Is there any reason why is it so? Also, what is the different of the time dependent mass [tex]m(t)[/tex] and let say a time dependent angular frequency [tex]\omega(t)[/tex] in a harmonic oscillator. it seems that the latter is allowed but not the mass. thank you!