“Black holes are an incredibly unique and fascinating feature of our universe,” said University of Queensland theoretical physicist, Joshua FooTheir mind-bending ability of having different masses simultaneously is what they are known for. “They’re created when gravity squeezes a vast amount of matter incredibly densely into a tiny space, creating so much gravitational pull that even light cannot escape. It’s a phenomenon that can be triggered by a dying star. But, until now, we haven’t deeply investigated whether black holes display some of the weird and wonderful behaviors of quantum physics.
Foo was the head of a UQ-led group of theoretical physicists who ran calculations that revealed unexpected quantum phenomena of black hole.
Superposition
“One such behavior is superposition, where particles on a quantum scale can exist in multiple states at the same time. This is most commonly illustrated by Schrödinger’s cat, which can be both dead and alive simultaneously. For black holes, however, we wanted to check if they could have drastically different masses at once. It turns out that they can. Imagine you’re both broad and tall, as well as short and skinny at the same time—it’s a situation which is intuitively confusing since we’re anchored in the world of traditional physics. But this is reality for quantum black holes.”
To reveal this, the team developed a mathematical framework allowing us to “place” a particle outside a theoretical mass-superposed black hole. Because mass is a key feature of black holes, it was specifically examined. It is also plausible that quantum blackholes would have mass superposition.
As a co-supervisor in research Dr. Magdalena ZychThe research supports the theories of pioneers of quantum Physics, according to them.
The universe is revealing to us that it’s always more strange, mysterious and fascinating than most of us could have ever imagined.”
“Our work shows that the very early theories of Jacob Bekenstein—an American and Israeli theoretical physicist who made fundamental contributions to the foundation of black hole thermodynamics—were on the money,” she said. “He postulated that black holes can only have masses that are of certain values, that is, they must fall within certain bands or ratios—this is how energy levels of an atom works, for example.
Quantum Gravity: Does it Cast Doubt on Fate of Black Holes’ Fate?
“Our modeling showed that these superposed masses were, in fact, in certain determined bands or ratios—as predicted by Bekenstein. “We didn’t assume any such pattern going in, so the fact we found this evidence was quite surprising. The universe is revealing to us that it’s always more strange, mysterious and fascinating than most of us could have ever imagined.”
It is often in such extreme environments where interesting and unexpected phenomena emerge.”
The Last Word
To send an email The Daily Galaxy, Joshua Foo wrote: “Our research is interested in the fundamental interplay between gravity and quantum mechanics, and so the scenario we’ve considered in the paper — a black hole in a superposition of masses — is obviously quite extreme. However it is often in such extreme environments where interesting and unexpected phenomena emerge — Stephen Hawking’s seminal discovery that black holes radiate particles is a good example of this.
What we show in our paper is an in-principle way of detecting the signatures of a black hole with a superposition of masses, in an analogous manner to how the gravitational wave detectors at LIGO measured “signatures” of the binary black hole merger in 2015. Observation of these signatures, while technically difficult, would nevertheless demonstrate the first example of Einstein’s gravity obeying the quantum superposition principle.
It is natural for people to wonder whether such astronomical suprapositions might occur in nature. The motion of several orbiting black holes (like the binary black hole merger detected by LIGO) will often become “chaotic”, such that the “quantum wave function” describing the black holes will spread rapidly, allowing for them to be characterized as being in a “superposition of locations”.
The example we give in the paper is perhaps simpler: Sending a “wavepacket” of light with different energies into a black hole will simultaneously impart different energies to the black hole, thus creating a superposition of black hole energies (and from Einstein’s theory of relativity we know that energy is directly related to mass).
The signatures of quantum black hole that we present in our paper, as I said, may not be visible with current technology. However, studying the in-principle effects that quantum black holes produce is important for understanding how the elusive theory that unifies quantum mechanics and gravity may be constructed.”
More information: Joshua Foo et al, Quantum Signatures of Black Hole Mass SuperpositionsPhysical Review Letters (2022). DOI: 10.1103/PhysRevLett.129.181301
Joshua Foo And University of Queensland
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