Synthetic black holes radiate like real ones

Research by the University of Amsterdam has demonstrated that the elusive radiation from black holes can be studied by mimicking it in the laboratory.

Black holes are the most extreme objects in the universe, packing so much mass into so little space that nothing, not even light, can escape their gravitational pull once they get close enough.

Understanding black holes is key to unraveling the most fundamental laws governing the cosmos, as they represent the limits of two of the best-tested theories in physics: the theory of general relativity, which describes gravity as resulting from deformation ( scale) of space-time by massive objects, and the theory of quantum mechanics, which describes physics at the smallest length scales. To fully describe black holes, we would need to put these two theories together and form a theory of quantum gravity.

Radiant black holes

To achieve this goal, we might want to look at what manages to escape black holes, rather than what gets swallowed. The event horizon is an intangible boundary around every black hole, beyond which there is no way out. However, Stephen Hawking discovered that every black hole must emit a small amount of thermal radiation due to small quantum fluctuations around its horizon.

Unfortunately, this radiation has never been directly detected. The amount of Hawking radiation coming from each black hole should be so small that it is impossible to detect it (with current technology) among the radiation coming from all other cosmic objects.

If not, could we study the mechanism underlying the emergence of Hawking radiation right here on Earth? This is what researchers from the University of Amsterdam and IFW Dresden set out to study. And the answer is an exciting “yes”.

Black holes in the lab

“We wanted to use the powerful tools of condensed matter physics to probe the inaccessible physics of these incredible objects: black holes,” says author Lotte Mertens.

To do this, the researchers studied a model based on a one-dimensional chain of atoms, in which electrons can “jump” from one atomic site to another. The warping of spacetime due to the presence of a black hole is mimicked by adjusting how easily electrons can hop between each site.

With the right jump probability variation along the chain, an electron moving from one end of the chain to the other will behave exactly like a piece of matter approaching the horizon of a black hole. And, analogous to Hawking radiation, the model system has measurable thermal excitations in the presence of a synthetic horizon.

Learn by analogy

Despite the absence of actual gravity in the model system, consideration of this synthetic horizon provides important insight into black hole physics. For example, the fact that the simulated Hawking radiation is thermal (meaning the system appears to have a fixed temperature) only for a specific choice of spatial variation in the jump probability, suggests that the actual Hawking radiation may also n be purely thermal in certain situations. .

Moreover, Hawking radiation only occurs when the model system starts up without any spatial variation in jump probabilities, mimicking a flat spacetime with no horizon, before being transformed into a system hosting a synthetic black hole. The emergence of Hawking radiation therefore requires a change in the warping of spacetime, or a change in how an observer looking for the radiation perceives this warping.

Finally, Hawking radiation requires that part of the chain exist beyond the synthetic horizon. This means that the existence of thermal radiation is intimately linked to the quantum mechanical property of entanglement between objects on either side of the horizon.

Because the model is so simple, it can be implemented in a range of experimental setups. This could include tunable electronic systems, spin chains, ultracold atoms or optical experiments. Bringing black holes to the lab can bring us closer to understanding the interplay between gravity and quantum mechanics, and on our way to a theory of quantum gravity.

The research has been published in Physical examination research.