# Is it true?

1. Jan 4, 2007

### Schrodinger's Dog

I was reading that apparently antimatter travels back in time according to Feynman(OK on the internet admittedly)

What implications does this have for QM?

More important is this actually factual or internet jabber.

Was Feynman correct in his assertion, and what is the current thinking about such strange ideas?

2. Jan 4, 2007

### cristo

Staff Emeritus
Feynman pointed out that the desription of a positron moving forward in time is identical to that of an electron moving backward in time, however I doubt he ever said "antimatter travels back in time."

3. Jan 4, 2007

### AlphaNumeric

Though this is pretty slap dash, I think a decent way to think about it is to consider the fourier components of the electron field. The 'matter' components have a term $$e^{-ip.x} = e^{i(Et - \mathbf{p.x})}$$ while the 'antimatter' components have $$e^{ip.x} = e^{i(-Et+ \mathbf{p.x})}$$ instead. There's a change in the sign of the 'iEt' term in the exponent. You can either interpret this as '-E' going in the +t direction (antimatter moving forward in time) or '+E' going in the '-t' direction (matter going backwards in time).

It's not very rigorous and I half expect someone will come along and set me right, but I think it's a fairly simple way of seeing how such an interpretation can come about.

4. Jan 5, 2007

### Schrodinger's Dog

Ok that sounds much more reasonable, the usual half stated half baked ideas you find on the web I guess. Interesting but not quite Earth shattering. Thanks guys

5. Jan 5, 2007

### Severian

This is called the Feynman-Stuckelberg Interpretation, and is used to get around having negative energy solutions of the wave equations.

6. Jan 5, 2007

### Schrodinger's Dog

Yeah I looked it up, thanks.

http://en.wikipedia.org/wiki/Antiparticle

I know how everyone hates wikipedia but it does have some relevant information, and seeing as the reference is Feynman should be fairly accurate..