What Makes Charged Black Holes Different from Uncharged Ones?

[Dmitry67]

Hi

I have few questions about charged BH.

1 I don't understand why the equations for the charged BH are different from BH without a charge. Why the gravitation, infinitely strong at the horizon, should 'care' about such minor additional forces like the electrical attraction/repulsion. Anyway, horizon is a point of no return as singularity becomes in the future for a free falling observer, no matter if he is charged or not. Additional electric repulsion would not 'save' the falling observer at the horizon.

2 Electron is orbiting a positively charged BH. QFT describes this attraction as exchange of virtual photons. But how can they pass thru the horizon?

3 Can BH have a color charge? Why not? Say green-antigreen u or d virtual quark pairs are torn abart at the horizon. What happens next?

Thank you

 

[George Jones]

Hi

I have few questions about charged BH.

1 I don't understand why the equations for the charged BH are different from BH without a charge. Why the gravitation, infinitely strong at the horizon, should 'care' about such minor additional forces like the electrical attraction/repulsion. Anyway, horizon is a point of no return as singularity becomes in the future for a free falling observer, no matter if he is charged or not. Additional electric repulsion would not 'save' the falling observer at the horizon.

Sorry, I don't understand this.

2 Electron is orbiting a positively charged BH. QFT describes this attraction as exchange of virtual photons. But how can they pass thru the horizon?

Roughly, virtual photons don't have to stay on the light-cone. See

http://math.ucr.edu/home/baez/physics/Relativity/BlackHoles/black_gravity.html.

3 Can BH have a color charge? Why not? Say green-antigreen u or d virtual quark pairs are torn abart at the horizon. What happens next?

Thank you

I thinks it's because, unlike the electromagnetic interaction, the colour force is not long-range, but I don't know the details.

String theorists play with black holes that have "exotic" charges.

 

[Dmitry67]

2 Correct, I forgot about it. Thank you
3 Well, residual strong force is short range, but the fundamental strong interaction is long range, because gluon is massless. It appears to be short range just because of the confinement, so the reason for being short range is very different from the reason why weak interaction is short range.

So I am still thinking about it.
If virtual pair is torn apart by the horizon then both BH and space outside are color-charged...