# Sakurai's treatment of Feynman's Path Integral

1. Oct 19, 2005

### mattlorig

I just finished reading Sakurai's treatment of feynman's path integral, and I'm left feeling really stupid. So the integral gives the propagator, which represents a transition amplitude. I'm left wondering what we use that for. Perhaps I'll understand when I start working some problems, or perhaps after I read the derivation a few more times. But, just to cover my bases, can anybody recommend a different source of the path integral derivation (which, according to sakurai really isn't a derivation)?

2. Oct 19, 2005

### Physics Monkey

The propagator is good for a lot of things. It gives you a complete solution to the Schrodinger equation for arbitrary initial conditions so that if $$K(x,t;x',t')$$ is the propagator then

$$\psi(x,t) = \int dx' \, K(x,t;x',0) \psi(x',0)$$

and $$\psi(x,t)$$ satisfies the Schrodinger equation. It can do a lot more too, it encodes all the information about the bound states and their energies.

Sakurai's treatment is rather terse. A great source for path integrals in general is "Techniques and Applications of Path Integration" by Schulman. A good online source is http://arxiv.org/abs/quant-ph/0004090

3. Oct 20, 2005

### straycat

Go straight to the source, Feynman himself! He is justly well-known for providing good physical pictures behind the math. See the thread "I need some bibliography" for some of his writings ...

David

4. Oct 25, 2005

### snooper007

I recommend the book by Ramond "Quantum field theory, a modern primer"
Path integral methods is a powerful tool in Quantum field theory,
particularly in Gauge field theory.

5. Oct 26, 2005

### dextercioby

I also like Cohen-Tannoudji's axiomatical treatmeant of path-integrals. In the first volume of his QM book.

Daniel.