How can Black Holes emit radiation?

[Lapidus]

Jackson, don't let them confuse you. The virtual particle picture is a perfectly fine *physical* explanation of what goes on with Hawking radiation.

 

[Cheese Donkey]

No, gravity need not be "strong" at the event horizon; there is no confining effect.

Here's the original paper:
http://prac.us.edu.pl/~ztpce/QM/CMPhawking.pdf
Particle Creation by Black Holes
S. W. Hawking
Commun. math. Phys. 43, 199—220 (1975)

Thanks for the link. It seems you need a strong base in quantum to completely understand the phenomenon. I'll have to bookmark this and save it for when I can understand the notation and the logic behind the math.

 

[Neandethal00]

Jackson, don't let them confuse you. The virtual particle picture is a perfectly fine *physical* explanation of what goes on with Hawking radiation.

Ok, I found the section in the Hawking paper that answers many of your questions. I put them bold.

As the mass of the black hole decreased, the area of the event horizon would
have to go down, thus violating the law that, classically, the area cannot decrease
[7, 12]. This violation must, presumably, be caused by a flux of negative energy
across the event horizon which balances the positive energy flux emitted to
infinity. One might picture this negative energy flux in the following way. Just
outside the event horizon there will be virtual pairs of particles, one with negative
energy and one with positive energy. The negative particle is in a region which
is classically forbidden but it can tunnel through the event horizon to the region
inside the black hole where the Killing vector which represents time translations
is spacelike. In this region the particle can exist as a real particle with a timelike
momentum vector even though its energy relative to infinity as measured by the
time translation Killing vector is negative. The other particle of the pair, having
a positive energy, can escape to infinity where it constitutes a part of the thermal
emission described above. The probability of the negative energy particle tunnelling
through the horizon is governed by the surface gravity K since this quantity
measures the gradient of the magnitude of the Killing vector or, in other words,
how fast the Killing vector is becoming spacelike. Instead of thinking of negative
energy particles tunnelling through the horizon in the positive sense of time one
could regard them as positive energy particles crossing the horizon on pastdirected
world-lines and then being scattered on to future-directed world-lines by
the gravitational field. It should be emphasized that these pictures of the mechanism
responsible for the thermal emission and area decrease are heuristic only
and should not be taken too literally. It should not be thought unreasonable that
a black hole, which is an excited state of the gravitational field, should decay
quantum mechanically and that, because of quantum fluctuation of the metric,
energy should be able to tunnel out of the potential well of a black hole. This
particle creation is directly analogous to that caused by a deep potential well in
flat space-time [18]. The real justification of the thermal emission is the mathematical
derivation given in Section (2) for the case of an uncharged non-rotating
black hole. The effects of angular momentum and charge are considered in
Section (3). In Section (4) it is shown that any renormalization of the energy-momentum
tensor with suitable properties must give a negative energy flow
down the black hole and consequent decrease in the area of the event horizon.
This negative energy flow is non-observable locally.

Read Hawking's disclaimer in RED. I'm not aware of particle creation in deep potential wells. The paper repeatedly mention 'particle creation'. Not sure if this particles are created from the collapsing mass by excessive heat or by 'vacuum fluctuation'?

 

[tom.stoer]

Hawkings speculates regarding a quantum state of the gravitational field - which is not what he has at hand b/c due to the lack of a full theory of quantum gravity his calculation is purely classical wr.t. the gravitation field. Nevertheless he introduces the idea of a large black hole being in an excited state and decaying quantum mechanically into a smaller black hole plus a particle.

Again in this picture you don't need any virtual particles - and Hawking doesn't use them during his calculation.