# Problem with propagator

1. Mar 18, 2005

### eljose

given the propagator:

$$G(x,t)=\frac{1}{e^{xt}+1}$$

and knowing that HG(x,t)=d(x-t) with d the "delta" function and H the Hamiltonian,then how could we construct (knowng G(x,t))the Hamiltonian?...

I one work i heard about the Green inverse function, how is it calculated?

2. Mar 18, 2005

### marlon

Well that is quite some work ? Are you expected to do that all on your own ? Normally you should have seen this in your QFT-course or your QM-course. It is an integral equation that you'll need to solve

regards
marlon

3. Mar 21, 2005

### dextercioby

I think you can use Fourier Transforms to find the Forurier transform of the operator you're looking for.

4. Mar 21, 2005

### marlon

Well, that's not all there is to it.

The OP must have seen some analoguous systems in his/her QFT-course, otherwise i really don't see the point of us starting to discuss this topic

marlon

5. Mar 21, 2005

### dextercioby

It's Jose.He's a "he".It doesn't seem like QFT to me...

6. Mar 21, 2005

### marlon

it has to be QM or QFT, you cannot tell which one based upon these data

marlon

7. Mar 27, 2005

### reilly

Try setting 1+exp(xt) = z. Then G=1/z, and work backwards from Poisson's Eq in z.

Regards,
Reilly Atkinson