# Creation of mass with velocity

1. Oct 21, 2015

### marlowgs

If I create an electromagnetic wave with electric and magnetic fields partially out of phase, would it behave the same as a mass with velocity less than the speed of light?

2. Oct 21, 2015

### Staff: Mentor

Would such a wave satisfy Maxwell's equations?

3. Oct 21, 2015

### marlowgs

In pair-production, a light wave (in-phase E&M) comes close to a heavy particle and turns into two masses with momentum, but the light wave needs to have a minimum energy to produce the particles. I’m wondering what happens if less than the minimum is there. Do the electric and magnetic fields go out of phase for a short time as the photon swipes past the heavy particle and does the partially out-of-phase photon act as an intermediate particle.

4. Oct 21, 2015

### Staff: Mentor

You're mixing up the classical and quantum views of light, and that's not going to end well.

For pair production, the only approach I've seen uses the quantum view of light, in which light isn't a wave, it's photons (heuristically speaking). Then there is no such thing as the electric and magnetic fields being in phase or out of phase, because you're not modeling the light as electric and magnetic fields.

I don't know if anyone has even tried to model pair production with the light being treated classically. I suspect it wouldn't work.

5. Oct 28, 2015

### vanhees71

It depends, which process you look at. If you have in mind pair production as the process $\gamma + \gamma \rightarrow \mathrm{e}^+ + \mathrm{e}^-$, I don't see, how you could describe this in classical terms.

The other extreme is the Schwinger mechanism, where a very strong static classical electric field leads to the spontaneous production of electron-positron pairs. So far this has not been observed in nature.

6. Oct 28, 2015

### harrylin

Interesting question! A quick search about "pair production in classical electrodynamics" yields a paper by A. Carati as well as more recently, a Powerpoint and a youtube presentation by Martin Land. Obviously it's "work-in-progress".