In the laboratory on Earth, we simulate the space-time behavior of a black hole in physical systems that are not themselves real black holes but are described by similar equations. Thus, we were able to test the existence of something similar to the evaporation of black holes due to the Hawking effect. But these were equivalent to non-rotating black holes. Physicists have now been able to simulate the case of rotating black holes, which will make it possible in the near future to test an analogue of the Hawking effect there as well.

We hoped to be able to create tiny black holes at the Large Hadron Collider (LHC), and we had good reasons for doing so, but the universe clearly had other black holes because they had not been discovered. These objects, which are considered fundamental keys to physics and astrophysics, are, unfortunately, not at our fingertips in the laboratory on Earth, at least it seems now, and there is no question of observing what is happening directly. Billions of light-years from the solar system, unless there is a small one MassMass in It rotates in orbitIt rotates in orbit around sunsun.

theory black holesblack holes It is a prediction by theory General relativityGeneral relativity toEinsteinEinstein. Solution EquationsEquations This theory is difficult to study mathematically and explain physically, largely because it is a nonlinear equation. But the big one physicalphysical John Wheeler realized that behaviorSpace-timeSpace-time It can be modeled by fluid behavior also described by nonlinear equations. While Einstein's theory describes variations in the geometry of space-time, Wheeler proposed visualizing it in terms of… partial similaritypartial similarity With hydrodynamics such as geodynamics. There will be observable quantum phenomena in infinitesimal objects that will be analogous to the production of foam, and rotating black holes will also have behavior similar to SwirlsSwirls In liquid.

## Analogues of black holes in fluids in the laboratory

Thus several black hole analogue models have been considered in experiments, in particular because it can be shown that a black hole analogue in a liquid should produce the quantum Hawking radiation equivalent of black hole evaporation at the level of sound waves. In liquid. The measurement is at the level of mathematical equations, but laboratory experimentation, even if limited to this type of physical system, makes it possible to test common mathematical calculations in false and real black holes.

We have reason to believe that behaviorHeliumHelium 4 in a country Super liquidSuper liquid,and thus able to flow without any resistanceresistancewith one ViscosityViscosity Zero when it is cooled near Absolute zeroAbsolute zero, is particularly close to the behavior of spacetime in general relativity due to its zero viscosity. In particular, it will make it possible to test related predictions Kerr black holesKerr black holesthose that are in a state of rotation, when they interact with the various physical fields around them, Electromagnetic fieldElectromagnetic field And gravity, of course, but possibly also that which describes particles ThemeTheme Ordinary and even dark matter such as axons.

## Quantum vortices in superfluid helium

Researchers from*University of Nottingham* (United Kingdom), in collaboration with their colleagues from *King's College London* And from here *Newcastle University*,announce, *via* Published in the famous newspaper *nature* Which can also be found for free at arXiv Specifically, he succeeded in producing a realistic space-time analogue around a Kerr black hole in superfluid helium-4 in the form of a celestial body. whirlpoolwhirlpool A large amount. This was necessary to be able to achieve detectable effects of their counterparts in black hole physics.

Creating a large quantum vortex, even if it is only a few millimeters in diameter, is far from straightforward. It was necessary to be able to combine a large number of elementary quantum vortices that tend not to stay together.

The name quantum vortex may sound esoteric, but the concept behind the name is not difficult to understand. It was introduced in 1949 by Norwegian physicist and chemist Lars Onsager, and developed a few years later by Richard Feynman.

In physics we know that Planck's constantPlanck's constant It has the dimension of action but also dimension Cinematic momentCinematic moment For a rotating body it finds itself quantum in the form of an integer or half an integer of Planck's constant just as there are discrete quantum states for a rotating body ElectronElectron in corncorn tohydrogenhydrogen. In helium-4 in the superfluid state, precisely because of quantum phenomena, the vortices in this superfluid also have quantum angular momentum since they are collections of rotating atoms. Thus the elementary quantum vortex is nothing but a vortex in this fluid with its own quantum angular momentum. Therefore, in their experiment, the British researchers were able to collect about 40,000 of these elementary quantum vortices.

*finally*Physicists also hope to test the Hawking radiation of rotating black holes with their new black hole counterpart. They have already observed the equivalent of quasi-normal patterns of black holes in helium.