Oh noes my friend.. Its not about negative energy, but background (void) temperature. The pair of particles (matter / anti-matter) spawn, cooling down the vacoom. Once they anihilate again, they change to energy (various photon emisions) increasing background temperature again. Thats why empty space is not at 0 kelvin. Every time such particle is absorbed by blackhole, it just increases it energy (and possibily mass). Not sure where that evaporation comes from ;)
There is no singular "it". I am responding to someone else who came to understand Hawking radiation through a thought experiment that Hawking himself described for pedagogical purposes.
A brief description of that thought experiment involving negative energy can be found here along with the appropriate citation coming from Hawking's "A Brief History of Time":
>Virtual particles can exist for a short period. When a pair of such particles appears next to a black hole's event horizon, one of them may get drawn in. This rotates its Killing vector so that its energy becomes negative and the pair have no net energy. This allows them to become real and the positive particle escapes as Hawking radiation, while the negative-energy particle reduces the black hole's net energy. Thus, a black hole may slowly evaporate.
