# A mini fractal universe may lie inside charged black holes (if they exist)

Perhaps the oddest and least understood objects in our universe are black holes. They have sucked in physicists for decades because they have so much promise, being related to anything from wormholes to new baby universes.

However, as weird as these known phenomena are, even stranger black holes could be imagined. A bizarre sort of black hole that is stranger than an M.C. Escher sketch could exist in one upside-down, hypothetical version of the universe. Now, a team of researchers has delved into the mathematical heart of so-called charged black holes and found a slew of surprises, including a space-time inferno and an unique fractal landscape… and possibly more.

### Welcome to a holographic superconductor

There are various types of potential, hypothetical black holes: those with or without an electric charge, those that spin or are stationary, those that are surrounded by matter or those that float in empty space. Some of these hypothetical black holes are known to occur in our universe; for example, the rotating black hole surrounded by infalling matter is quite common. We’ve even photographed one.

Other kinds of black holes, on the other hand, are totally theoretical. Physicists are still interested in researching them, since by delving into their mathematical foundations, we can discover new connections and implications of our physical theories, which can have real-world implications.

One such theoretical black hole is an electrically charged black hole surrounded by an anti-de Sitter space. Without going too scientific, this type of space has constant negative geometric curvature, similar to a horse saddle, which we all know is not a good description of our reality. (All else being equal, a universe with anti-de Sitter space would have a negative cosmological constant, which means that any matter would tend to condense into a black hole, as opposed to the known accelerating expansion that is flinging the universe apart.

This horse-saddle space does not exist in our universe, but that’s good because these unusual black holes contain incredibly intricate structures that are worth exploring.

One reason it’s worth investigating is that charged black holes have many similarities to rotating black holes, which actually exist in our universe, but charged black holes are mathematically easier to understand. We can learn more about real-world rotating black holes by researching charged black holes.

Furthermore, physicists have discovered that when these black holes cool, a “haze” of quantum fields develops around their surfaces. This haze sticks to the surface, pulled inward by the never-tiring gravity of the black hole itself, but pushed outward by the electric repulsion of the same black hole. A superconductor is a haze of quantum fields functioning in stability on a surface. Because superconductors have real-world uses (they can transport electric current with no resistance), seeing how they behave in these exotic settings helps us comprehend their mathematical structures, which may lead to new insights with real-world applications.

A team of academics recently employed the language of superconductivity to determine what lies further beneath the surface of these hypothetical black holes in a study published to the preprint database arXiv.

### The almost-wormhole

“Normal” charged black holes — those surrounded by our universe’s standard space-time — contain a few quirks on the inside. First, beyond the event horizon (the boundary of every black hole, where once you fall in, you can’t get out), there’s something called an inner horizon, which is a region of intense quantum energies. Beyond that is a wormhole, a bridge to a white hole in some other lonely section of the universe (at least, according to mathematics).

I should point out that we don’t know whether wormholes like this occur in reality because the mathematics of charged black holes breaks down at the inner horizon, and nothing more can be learnt until new physics is developed. Fortunately, charged black holes surrounded by anti-de Sitter space, which we’ll refer to as superconductor black holes for the time being, are immune to this difficulty.

The good news is that the inner horizon of a superconducting black hole collapses, allowing you to fly past it without becoming spaghettified, as you would in a normal, stationary black hole. The bad news is that the wormhole bridge within a superconducting black hole splits itself apart, thus you won’t be able to travel to distant stars.

That doesn’t mean nothing exciting happens to you. The inside of a superconductor black hole becomes frothy just inside what would have been the inner horizon.

Normally, particles in real-life superconductors can oscillate, allowing waves to slide back and forth in a phenomenon known as Josephson Oscillations. Space itself vibrates back and forth deep within these black holes. If you were to fall into one of these creatures, you’d be in for a rough ride.

### A strange universe

What happens once you go passed the vibrating space-time is genuinely mysterious. The researchers observed that the innermost parts of a superconducting black hole can have a grotesque miniature expanding universe, where space can stretch and deform at various rates in different directions.

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

It would be a tiny fractal universe, repeating indefinitely from vast to minute scales. It’s difficult to imagine what it would be like to go through such a landscape, but it would undoubtedly be strange.

The singularity: the point of infinite density, the location of every bit of stuff that has ever fallen into the black hole resides at the center of this odd fractal, chaotic mess.

Unfortunately, the researchers are still unable to describe what happens at the singularity using their supercharged superconducting mathematical approaches. All known physics fails, requiring the development of new gravity theories.

Who knows what you’ll find at the center of a superconductor black hole, but you’ll have a good time going there.