According to quantum mechanics, a vacuum state is populated by virtual particle pairs undergoing spontaneous creation and annihilation processes. These quantum fluctuations can turn into real particle pairs in the presence of a background field. The most prominent example of such a process is the Schwinger effect predicting the creation of charged particle pairs in the presence of an electric field. In new research, astrophysicists at Radboud University show the existence of a local gravitational particle production mechanism in curved spacetimes similar to the Schwinger effect for electric fields.
Wondrak et al. present a new avenue to black hole evaporation using a heat-kernel approach analogous as for the Schwinger effect. Image credit: Sci.News.
“Using a clever combination of quantum physics and Einstein’s theory of gravity, Stephen Hawking argued that the spontaneous creation and annihilation of pairs of particles must occur near the event horizon,” said Radboud University scientist Michael Wondrak and his colleagues.
“A particle and its antiparticle are created very briefly from the quantum field, after which they immediately annihilate.”
“But sometimes a particle falls into the black hole, and then the other particle can escape — Hawking radiation.”
“According to Hawking, this would eventually result in the evaporation of black holes.”
In their new research, the researchers revisited this process and investigated whether or not the presence of an event horizon is indeed crucial.
They combined techniques from physics, astronomy and mathematics to examine what happens if such pairs of particles are created in the surroundings of black holes.
They demonstrated that new particles can also be created far beyond this horizon.
“We demonstrate that, in addition to the well-known Hawking radiation, there is also a new form of radiation,” said Dr. Wondrak, first author on the study.
“We show that far beyond a black hole the curvature of spacetime plays a big role in creating radiation,” added co-author Dr. Walter van Suijlekom.
“The particles are already separated there by the tidal forces of the gravitational field.”
Whereas it was previously thought that no radiation was possible without the event horizon, the authors found that this horizon is not necessary.
“That means that objects without an event horizon, such as the remnants of old stars and other large objects in the Universe, also have this sort of radiation,” said co-author Dr. Heino Falcke.
“And, after a very long period, that would lead to everything in the Universe eventually evaporating, just like black holes.”
“This changes not only our understanding of Hawking radiation but also our view of the Universe and its future.”
The team’s paper was published in the journal Physical Review Letters.
_____
Michael F. Wondrak et al. 2023. Gravitational Pair Production and Black Hole Evaporation. Physical Review Letters, in press; arXiv: 2305.18521
