# Finding Feynman's propagator

1. Dec 18, 2011

### Morgoth

Well I am doing an assignment concerning methods of finding Feynman's propagator.

I understand pretty well how everything's coming up. I also get that the form:
<x'',t'|x',0> defined as Feynman's propagator gives the amplitude of a system initially being in state |x',0> to be in |x'',t> after time t.

What I don't get is after you use Schwinger's Method to calculate Feynman's propagator for the Harmonic Oscilator you end up in a form:
<x'',t'|x',0>=SQRT[mω/2πihsin(ωt)] * exp{ (imω/2hsin(ωt))* [(x''^2- x'^2)cos(ωt)-2x''x'] }

(Sorry for the not beautiful formula).

In fact I cannot understand what kind of information the above form gives us.
+
For the amplitude the change of x''->x' and x'->x'' would be a symmetry since they are both into the exp[if] which is just a phase factor?

Can anyone give me an idea? Thanks

Last edited: Dec 18, 2011