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You can make a black hole with only matter, but Hawking radiation involves the emission of both matter and antimatter. If a star made out of matter (including baryons) collapses into a black hole, and then the black hole evaporates, will Baryon number conservation be violated? Can this process be played in reverse to turn equal parts matter and antimatter into mostly matter?

Retracted
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  • https://physics.stackexchange.com/questions/482659/what-is-really-a-negative-energy-particle-and-why-is-it-different-from-an-anti – Árpád Szendrei Jun 02 '19 at 21:55
  • https://physics.stackexchange.com/questions/30597/black-holes-and-positive-negative-energy-particles – Árpád Szendrei Jun 02 '19 at 21:56
  • I don't see how those are related. – Retracted Jun 02 '19 at 22:04
  • you are saying/asking whether when the BH evaporates, it violates baryon conservation because the evaporation involves (as you state) antimatter. The evaporation does not involve antimatter, but negative energy particles. The two are not the same thing. I tried to cite John Rennie, and give you a few links where it is discussed. – Árpád Szendrei Jun 02 '19 at 22:07
  • So, antimatter is never emitted from an evaporating black hole? – Retracted Jun 02 '19 at 22:09
  • correct. it involves virtual particle pairs. it is an entangled pair. one is negative energy, one is positive energy. after the interaction with the black hole, the positive energy particle leaves (outside) the BH, the negative energy particle is swallowed by the BH. – Árpád Szendrei Jun 02 '19 at 22:14
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    Antiparticles have positive energy. What you are saying does not mean that black holes can't emit antimatter. – Retracted Jun 02 '19 at 22:22
  • No. The antiparticle-particle pair is created outside the EH. Not inside the BH. This radiation (matter-antimatter) does not come from the BH itself, but from the virtual particles (becoming real), caused by the gravitational field of the BH. – Árpád Szendrei Jun 02 '19 at 22:33
  • the vacuum fluctuation causes the particle-antiparticle pair to appear near the event horizon. The one that is swallowed by the BH, must have negative energy, to obey conservation of energy laws with respect to a far away observer. – Árpád Szendrei Jun 02 '19 at 22:34
  • because the negative energy particle is swallowed by the BH, the BH loses energy. – Árpád Szendrei Jun 02 '19 at 22:34
  • it is very important to understand that the particle-antiparticle pair is not emitted by the BH. – Árpád Szendrei Jun 02 '19 at 22:35
  • @ÁrpádSzendrei While pairs certainly are not emitted, a particle can be emitted from one particle/antiparticle pair and later an antiparticle can be emitted from a different particle/antiparticle pair. So overall both particles and antiparticles are emitted in the equal proportion (assuming the Hawking radiation exists). – safesphere Jun 03 '19 at 09:20

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