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An international team of researchers has just discovered that inside a theoretical type of black holes can exist **authentic expanding universes**, although in them things would be completely different from what we are used to.

Sean Hartnoll, from the Stanford University Institute for Theoretical Physics and first author of an article published in ArXiv believes, in effect, that an electrically charged black hole surrounded by a certain type of space known as **“anti de Sitter”** it could hold within it, beyond the horizon of events, the grotesque miniature of an expanding universe.

Of course, such black holes do not exist in our Universe, and one of the reasons, as the astrophysicist explains **Paul Sutter** in LiveScience, is that “this type of space (the anti De-Sitter) has a negative geometric curvature, so it would have a negative cosmological constant, which means that any matter will tend to condense into a black hole”. Something that would be just the opposite of what we see in our Universe, which is expanding rapidly and in which matter tends to be increasingly separated.

### The advantages of “impossible physics”

Delving into this “impossible physics”, however, has multiple advantages. And it is that those hypothetical charged black holes and in an “upside down” universe share many similarities with the real rotating black holes that do exist in our Universe, and it turns out that from the mathematical point of view they are much easier to approach. Therefore, by studying them, it is possible to obtain important insights about real black holes. As Sutter explains, although these black holes are purely theoretical, “we physicists are interested in exploring them because by diving into their mathematical foundations, we can discover new relationships and implications of our physical theories, which can have consequences in the real world.” .

“Normal” charged black holes, that is, those that are surrounded by a typical spacetime, have a series of peculiarities within them. For example, beyond the event horizon (the limit beyond which nothing that enters can leave again), there is something called the “inner horizon”, a region that bubbles with intense quantum energies. And even beyond that internal horizon, the theory tells us that there should be a wormhole, a “bridge” to other distant regions of the Universe.

Until now, no one has seen a wormhole in real life yet, because the mathematics of charged black holes breaks down at the inner horizon, so from there it is no longer possible to learn anything else, at least, until totally new physics is developed. However, charged black holes surrounded by anti-De-Sitter space, also called “superconductors,” avoid this problem and allow scientists to (mathematically) dive into them much deeper.

That is precisely what Sean Hartnoll and his colleagues have done. And when crossing the forbidden border of the inner horizon they have encountered something strange and totally unexpected.

### An oscillating space time

Normally, superconductor particles that exist in real life can oscillate, creating waves that move back and forth in an effect known as **“Josephson Oscillations”.** But on the inner horizon of these theoretical black holes, what vibrates from one side to another is not the particles, but space itself. But it is even further, after crossing that area and leaving the inner horizon behind, when things become really disconcerting.

The researchers, in fact, discovered that at the heart of a superconducting charged black hole there can be veritable miniature expanding universes, chaotic places where space can stretch and warp at different speeds and in different directions.

What’s more, depending on the temperature of the black hole, some of these regions of space can trigger a new wave of vibrations, which would then create a new patch of expanding space, and so on at smaller and smaller scales.

As Sutter explains in Live Science, “it would be a **mini fractal universe**, repeating itself infinitely from large to small scales. It is absolutely impossible to describe what it would be like to go through such a place, but it would surely be very disturbing. At the center of that strange chaotic, fractal disorder is the singularity, the point of infinite density, the place where every bit of matter that ever fell into the black hole resides. “

“Unfortunately,” continues the astrophysicist, “even with their supercharged superconducting mathematical techniques, researchers cannot describe what happens at the singularity. There all known physics breaks down, and new theories of gravity are required to fully understand it.”

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