A new type of black hole analogue could tell us a thing or two about the theoretically elusive radiation emitted by the real thing.
Using a string of atoms in a single file to simulate a black hole’s event horizon, a team of physicists has observed the equivalent of what we call Hawking radiation – particles generated by perturbations in the quantum fluctuations caused by the black hole’s fracturing of space-time.
This, they say, could help resolve the tension between two currently irreconcilable frameworks for describing the universe: general relativity, which describes the behavior of gravity as a continuous field known as space-time; and quantum mechanics, which describes the behavior of discrete particles using the mathematics of probability.
For a unified theory of quantum gravity that can be applied universally, these two theories that don’t mix need to find a way to fit in somehow.
This is where black holes come into the picture – perhaps the strangest and most extreme things in the universe. These massive objects are so incredibly dense that there is not enough velocity to escape in the universe within a certain distance from the center of mass of the black hole. Not even the speed of light.
This distance, which varies depending on the mass of the black hole, is called the event horizon. Once a body goes beyond its limits, we can only imagine what happens, as nothing returns vital information about its fate. But in 1974, Stephen Hawking proposed that discontinuities in the quantum fluctuations caused by the event horizon give rise to a type of radiation very similar to thermal radiation.
If Hawking radiation exists, it would be too faint for us to detect it yet. We may never sort it out from the still hissing of the universe. But we can investigate its properties by creating analogues of a black hole in laboratory settings.
This has been done before, but now a team led by Lotte Mertens of the University of Amsterdam in the Netherlands has done something new.
A string of one-dimensional atoms served as a path for Electrons to “jump” from one location to another. By adjusting the ease with which this hopping can occur, physicists can cause certain properties to disappear, effectively creating a kind of event horizon that overlaps the wave-like nature of electrons.
The team said that this faked event horizon effect resulted in a rise in temperature that matches theoretical predictions for an equivalent black hole system, But only when part of the chain extends beyond the event horizon.
This could mean that entanglement of particles that extends across the event horizon is useful in generating Hawking radiation.
The simulated Hawking radiation was only thermal to a certain range of amplitude jumps, and below that simulations started to mimic a type of space-time considered “flat”. This indicates that Hawking radiation may only be convective within a range of situations, and when there is a warp change in space-time due to gravity.
It’s unclear what this means for quantum gravity, but the model offers a way to study the emergence of Hawking radiation in an environment unaffected by the wild dynamics of black hole formation. Because it is so simple, the researchers said, it can be run in a wide range of experimental settings.
“This could open the field for exploration of fundamental aspects of quantum mechanics along with gravity and curvilinear voids in various condensed matter settings,” the researchers write.
Research published in Physical review research.
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