# Hawking radiation & quarks/gluons

1. Sep 3, 2010

### Quqzar

The theory of "Hawking radiation" says that black holes can emit different particles. We have a particle-antiparticle pair and one of them falls into the black hole while the other one escapes.

On the other hand, we know that particles with color charge like quarks or gluons cannot travel freely.

So my question is simple: Can black hole emit quarks or gluons ?

I would be grateful if you could make it more understandable for me.

2. Sep 3, 2010

### nickthrop101

although im not certain with the answer, from intuition i would think that the amount that the blaCK HOLE RELEASES (the energy) would not be enough to create a quark or a gluon, as the energy releases is in the form of heat and the only reason it produces particlles is that it rips one pair of particle from the other, so one zooms into space and the other is absorbed :)

3. Sep 3, 2010

### tom.stoer

The black hole would certainly produce quarks and gluons at the horizon, but asymptotically they would not appear, but would be converted into hadrons.

Afaik Hawkings paper deals with a free, scalar theory on a Schwarzschild spacetime. He defines asymptotic states on that spacetime and derives the spectrum. For quarks and gluons this is certainly not allowed; instead one would have to formulate a theory of strongly interacting particles, i.e. QCD on top of the Schwarzschild spacetime. I don't know whether anybody has ever tried to do this.

4. Sep 3, 2010

### Quqzar

OK. Thanks for replies. But I think the problem is still unsolved. Even if black holes dont actually emit single quarks (because they dont have enough energy or because these quarks will be converted into hadrons finally), the mere fact they would have possibility to do it (in some unusual conditions) should be worrisome. It looks for me like a inexplicable contradiction in the way we describe quantum physics & black holes.

5. Sep 3, 2010

### tom.stoer

Why?

What's the fundamental difference between scalar particles, photons and gluons regarding Hawking radiation?

6. Sep 3, 2010

### Quqzar

Maybe I dont understand this issue properly, but it seems to me there is important difference.

According to quantum chromodynamics, the energy of quark-quark interaction is increasing together with distance between them. If somebody tries to separate a quark, the energy will be increasing until a new pair quark-antiquark will appear.

Lets think about the black hole. Lets suppose that two separate quarks were created (during Hawking radiation of course) in the same moment of time, and the distance between them is, for example, 100 times greater that it is needed to create new quark-antiquark pair. Then, the energy of ineraction between them should be enormous. Am I right ?

7. Sep 3, 2010

### Dmitry67

Yes, I was thinking about it too.
Imagine big BH - it emits quarks, but very very rarely.
So it emits its first quark breaking colorless quark-antiquark pair.
The free quark HAS color!

8. Sep 3, 2010

### tom.stoer

A single quark will not escape to infinity.

9. Sep 4, 2010

### Quqzar

So, what will single quark do ?

"Converting into hadrons" about which You wrote need to be extremely quick if You want to avoid enormous energy effect this way. The problem is not only a single quark somewhere in infinity. The problem would begin when a single quark would start to exist (even near to the black holes horizon), because it would (probably) interact with other single quark. The energy of this interaction should increase (?) if the distance between quarks is greater than usual.

10. Sep 4, 2010

### tom.stoer

I agree that this is a problem; but as I said, the problem is NOT regarding the production of free quarks at the horizon but about the asymptotic states. Near the horizon the quark-antiquark pairs do not behave fundamentally different than in flat space. That's why one can safely assume that they appear. The problem is how to claculate the strong interaction between them = the hadronization in a curved background and they asymptotic states.

11. Sep 5, 2010

### Dmitry67

Anyway, if a single free quark would be somehow ejected from the black hole, what we would observe? That extra color charge would be always conserved in any interactions, so that weirdness cant dissipate...

12. Sep 5, 2010

### tom.stoer

It is clear that a large separation of a quark from its antiquark is possible only in huge gravitational fields. But of course single colored particles would be confined and screened by hadronization. So I guess that we would observe a bunch of hadrons from the black hole, not a single quark. The color charge stays closed to its anticharge near the horizon and is eventually trapped inside the BH.

Interesting question!

13. Sep 5, 2010

### haael

I bet that some kind of quantum entanglement would allow ejecting only color-neutral particles.

Imagine color current as a time loop. Gravity can stretch this loop to some extraordinary size, but cannot break it, i.e. it cannot transform it into a line so that one end of this line ends in singularity and the other goes to infinity.
The only possible situation is that the equal amount of color current enters and exits the hole. That means, the color charge is conserved independently inside and outside of the horizon. Also, even if the two oppositely colored quarks should exit the hole far away of each other, virtual quark pairs would make a "bridge" between them to screen their color, then this "bridge" would hadronize quickly.

14. Sep 6, 2010

### Dmitry67

Hm... Can you satisfy this condition everywhere knowing that position of the apparent horizon is observer-dependent? So for any proton near BH there might be an observer who sees that proton cut in 2 pieces by his apparent horizon?

Hm, but the number of particles is also observer-dependent....

15. Sep 6, 2010

### tom.stoer

Again: I am convinced that you cannot separate a single color charge from the black hole.

16. Sep 6, 2010

### haael

Yes, you can see a proton cut by an event horizon. However, you still cannot see its color current loops cut.

Me too.