I Charged Particle Free Fall in Grav Field: Does Anyone Know Answer?

[lerus]

TL;DR Summary

Will a charged particle, free falling in a gravitation field, emit electromagnetic waves?

From one point of view the charged particle is accelerating and should emit electromagnetic waves.
But from the equivalence principle, I think, it should not.
Does anybody know the answer?

 

[Keith_McClary]

https://www.google.com/search?q=charged+particle,+free+falling+in+a+gravitation+field

 

[lerus]

Thanks a lot, somehow I didn't find it myself.
But is it possible that for in free falling observer particle doesn't radiate but for supported observer radiation exists?
I think I have to read the article.

 

[Keith_McClary]

I think I have to read the article.

That's not my specialty, so you will know more than I.

 

[A.T.]

Summary:: Will a charged particle, free falling in a gravitation field, emit electromagnetic waves?

From one point of view the charged particle is accelerating and should emit electromagnetic waves.
But from the equivalence principle, I think, it should not.
Does anybody know the answer?

There are related threads about a charge hovering in gravitational field:
https://www.physicsforums.com/threads/paradox-electron-radiates-in-a-gravitational-field.950608/

 

[otennert]

This is not at all a trivial problem, but some notable authors have already written papers on this: see some references here: https://inspirehep.net/literature/44837 and a recent Review Article by Øyvind Grøn.

In the end it boils down to the result that the question of whether radiation takes place or not is not invariant against general transformations involving acceleration. A comoving observer does not observe radiation of a freely falling charge, whereas a stationary observer does.

 

[lerus]

Thank you for the links.

I saw similar results in other places but it is difficult to understand how it is possible that one observer observes radiation when another doesn't. Radiation takes energy and momentum - it means if charge radiates then it will not follow geodesics. But if there is no radiation then it will (I think) follow geodesics.

Anyways, I'll try to read papers that you mentioned.

 

[A.T.]

I saw similar results in other places but it is difficult to understand how it is possible that one observer observes radiation when another doesn't. Radiation takes energy and momentum

Energy and momentum are frame dependent as well.

But if there is no radiation then it will (I think) follow geodesics.

Depends on the frame. A charge with constant proper acceleration doesn't follow geodesics (frame invariant fact). But in its non-inertial rest frame it doesn't radiate, it just has a distorted (non-radial field). See image (b) below.

In that context it might be helpful to use images where the acceleration is constant (b), not changing (a):

From: https://arxiv.org/abs/1503.01150