Does Gravity Cause Accelerating Charged Particles to Emit EM Radiation?

[Drakkith]

An accelerating charged particle produces EM radiation. Does gravity cause this effect as well? Does the particle actually accelerate due to it or would it not since it would be following a straight path through curved spacetime? I'm guessing the particle would not create EM radiation, but I'm not sure.

Thanks!

 

[bcrowell]

Are you asking whether a free-falling, neutral massive particle radiates gravitational waves? In that case, yes, it does.

Or are you asking whether a free-falling, charged particle radiates EM waves? That one's a can of worms.

 

[Drakkith]

Thanks Bcrowell. I was referring to the 2nd one. Was my reasoning sound?

 

[bcrowell]

That issue is complicated. Here are some threads we've had about it:

https://www.physicsforums.com/showthread.php?t=369612
https://www.physicsforums.com/showthread.php?t=407292
https://www.physicsforums.com/showthread.php?t=405125

 

[Drakkith]

Oh wow, I didn't realize it was so complicated, I assumed it was a simple answer lol. I'll read over those threads. Thanks again!

 

[Bill_K]

I once attended a seminar by Bryce DeWitt on this topic, and there's no one in relativity whose opinion I trust more. And Bryce says they radiate, and so they radiate! Here's the paper: C. Morette-DeWitt and B.S. DeWitt, "Falling Charges," Physics, 1,3-20 (1964)

 

[bcrowell]

I once attended a seminar by Bryce DeWitt on this topic, and there's no one in relativity whose opinion I trust more. And Bryce says they radiate, and so they radiate! Here's the paper: C. Morette-DeWitt and B.S. DeWitt, "Falling Charges," Physics, 1,3-20 (1964)

The impression I get is that they do radiate, for some definitions of "radiate." They also don't radiate, for some other definitions of "radiate."

 

[Bill_K]

Radiate means the electromagnetic field goes as 1/r at future null infinity.

 

[bcrowell]

Radiate means the electromagnetic field goes as 1/r at future null infinity.

Again, this is just my impression from a casual reading of the literature, but my impression is that if everyone agreed on what the appropriate definition was, then the debate would have been over 40 years ago. If you look through some of those threads I linked to, you can find a dozen papers debating this back and forth over a period of decades. I'm not saying that your proposed definition is wrong, but (a) it's not obvious (to me) that it is completely rigorously well defined, and (b) it's not obvious (to me) whether there might be definitions that would be inequivalent to it and equally attractive. This whole business of self-force in curved spacetime is really tough.