Dead Stars Don't Radiate

Summary

Three guys claim that any heavy chunk of matter emits Hawking radiation, even if it’s not a black hole: • Michael F. Wondrak, Walter D. van Suijlekom and Heino Falcke, Gravitational pair production and black hole evaporation, Phys. Rev. Lett. 130 (2023), 221502. Now they’re getting more publicity by claiming this means that the universe will fizzle out sooner than we expected. They’re claiming, for example, that a dead, cold star will emit Hawking radiation, and thus slowly lose mass and eventually disappear! They admit that this would violate baryon conservation: after all, the protons and neutrons in the star would have to go away somehow! They admit they don’t know how this would work. They just say that the gravitational field of the star will create particle-antiparticle pairs that will slowly radiate away, forcing the dead star to lose mass somehow to conserve energy. If experts thought this had even a chance of being true, it would be the biggest thing since sliced bread—at least in the field of quantum gravity. Everyone would be writing papers about it, because if true it would be revolutionary. It would overturn calculations by experts which say that a stationary chunk of matter doesn’t emit Hawking radiation. It would also mean that quantum field theory in curved spacetime can only be consistent if baryon number fails to be conserved! This would be utterly shocking. But in fact, these new papers have had almost zero effect on physics. There’s a short rebuttal, here: • Antonio Ferreiro José Navarro-Salas and Silvia Pla, on “Gravitational pair production and black hole evaporation”, Phys. Rev. Lett. 133 (2024), 229001. It explains that these guys used a crude approximation that gives wrong results even in a simpler problem. Similar points are made here: • E. T. Akhmedov, D. V. Diakonov and C. Schubert, Complex effective actions and gravitational pair creation, Phys. Rev. D. 110, 105011. Unfortunately, it seems the real experts on quantum field theory in cur...