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I was reading this post Black holes and positive/negative-energy particles because I was wondering how Hawking radiation works and why always the anti-particle falls into a black hole, which is nicely explained there.

However, I feel that I have an understanding problem what vacuum fluctuation really is. Is it a pair of particle-anti-particle, e.g. electron and positron (as I assumed...) or positive-negative-mass-particle? If the latter is true, what is the negative particle then, surely not a positron...?

Matter/antimatter or matter/negative-matter is not the same and it's important when understanding Hawking radiation (as in the post mentioned above). That is because anti-particles like positrons have still positive mass, thus falling into the black hole would just grow the hole. (Or in other words: If we would produce antimatter in particle accelerators and pour it into a black hole, it would grow, correct?)

Also, if vacuum fluctuations consist of positive and negative mass (or energy), the annihilation would produce zero energy, whereas I thought the explanation for vacuum fluctuations is some remaining "zero-point-energy" in quantum mechanics... thus I assumed real antimatter.

Charles Tucker 3
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1 Answers1

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However, I feel that I have an understanding problem what vacuum fluctuation really is.

It is hypothetical loops or particle-antiparticle pairs. Hypothetical because if there is no real particle with a fourvector from which the loop can get some energy, there is no way to detect it. Loops of particle-antiparticle are in higher order Feynman diagrams and are used to get better calculations for observables as crossections and decays.

vacuum loops

However, I feel that I have an understanding problem what vacuum fluctuation really is. Is it a pair of particle-anti-particle, e.g. electron and positron (as I assumed...) or positive-negative-mass-particle? If the latter is true, what is the negative particle then, surely not a positron...?

The invariant mass of elementary particles that can be in particle antiparticle pairs is always larger than zero, neutrinos, electron-positron, quark-antiquark....

That is because anti-particles like positrons have still positive mass, thus falling into the black hole would just grow the hole

Not true. The hypothetical loop pair of electron-positron takes its four vector (energy/momentum) from the fields of the horizon. When the electron is absorbed because its momentum was pointing down to the black hole, the positron escapes with its part of the energy/momentum, (vice verso for positron electron)and thus the black hole loses mass, not gains.

If we would produce antimatter in particle accelerators and pour it into a black hole, it would grow, correct?)

That antimatter would not have any connection with the black hole, and by falling in would increase the mass of the black hole. Hawking radiation takes energy/momentum out of the black hole, that is why micro black holes from the Big Bang are supposed to have evaporated by now.

anna v
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