Why can Hawking Radiation not work in reverse?

[rollcast]

I understand that to obey conservation that the black hole must lose energy and mass and the surrounding space must gain an equal amount of energy and mass.

Then why can the antiparticle not be emitted from the black hole, adding negative energy and mass to the surrounding space, and the other particle goes to the singularity and adds positive energy and mass to the black hole?

Surely this still obeys conservation as the surrounding space appears to lose energy and mass, by the addition of negative energy and mass, and the black hole will gain an equal amount of energy and mass?

Thanks
AL

[George Jones]

From the end of

http://www.physics.ucdavis.edu/Text/Carlip.html#Hawkrad.

Note that this doesn't work in the other direction -- you can't have the positive-energy particle cross the horizon and leaves the negative- energy particle stranded outside, since a negative-energy particle can't continue to exist outside the horizon for a time longer than h/E. So the black hole can lose energy to vacuum fluctuations, but it can't gain energy.

[twofish-quant]

Then why can the antiparticle not be emitted from the black hole, adding negative energy and mass to the surrounding space, and the other particle goes to the singularity and adds positive energy and mass to the black hole?

Antiparticle != negative energy. Any antiparticle is going to have positive energy.

Also energy is not absolute but relative to something. The vacuum around a black hole has non-zero energy due to the gravitational field and the field can generate particle/anti-particle pairs with the one of the pairs falling into the event horizon.

I'm not sure that I agree with Carlip's explanation. Frequencies don't have a sign, and antimatter always has positive energy.

Also Hawking radiation can work in reverse. If you put a black hole in a warm heat bath, you are increasing the "zero level" of the space around it, and then you cause radiation to flow into the black hole making it bigger.

[Drakkith]

Twofish, isn't that happening with pretty much all black holes by absorbing the CMB?

[ibysaiyan]

Antiparticle != negative energy. Any antiparticle is going to have positive energy.

Also energy is not absolute but relative to something. The vacuum around a black hole has non-zero energy due to the gravitational field and the field can generate particle/anti-particle pairs with the one of the pairs falling into the event horizon.

I'm not sure that I agree with Carlip's explanation. Frequencies don't have a sign, and antimatter always has positive energy.

Also Hawking radiation can work in reverse. If you put a black hole in a warm heat bath, you are increasing the "zero level" of the space around it, and then you cause radiation to flow into the black hole making it bigger.
Hi,
Can you clarify what you mean't by "zero level" above. Is it temperature relative to the BH ?