Our Universe May be a Hologram: Theory of Theoretical Physics Challenges 3D Assumption

To us, the universe looks three dimensional. But one of the theories of theoretical physics challenges this assumption. The "holographic principle" suggests that a mathematical description of the universe actually requires one fewer dimensions than it seems. What we perceive as three dimensional may just be the image of two dimensional processes on a huge cosmic horizon. Now, scientists are taking a closer look at this theory.

The principle, until now, has only been studied in exotic spaces with negative curvature. These spaces, though, are different from the space in our own universe. Now, researchers have found that the holographic principle holds in a flat spacetime.

Everyone knows about holograms; you can see them in credit cards or even on dollar bills. While they're two dimensional, they appear three dimensional to us. Now, scientists suggest that our universe could behave similarly.

Gravitational phenomena are described in a theory with three spatial dimensions. The behavior of quantum particles is actually calculated in a theory with just two spatial dimensions, and the results of both calculations can be mapped onto each other. This is surprising, but the method is also successful.

For theoretical physics, this correspondence is important. However, it doesn't seem to have much to do with our own universe, since the spaces used are negatively curved. In contrast, our own universe is quite flat and on astronomical distances, has a positive curvature.

In order to see if a correspondence principle holds true for our real universe, the researchers worked on gravitational theories which do not require exotic spaces.

"If quantum gravity in a flat space allows for a holographic description by a standard quantum theory, then there must be physical quantities, which can be calculated in both theories-and the results must agree," said Daniel Grumiller, one of the researchers, in a news release.

When quantum particles are entangled, they cannot be described individually. They form a single quantum object, even if they are located far apart. There is also a measure for the amount of entanglement in a quantum system, called "entropy of entanglement." In this latest study, the scientists managed to show that this entropy of entanglement takes the same value in a flat quantum gravity and in a low dimension quantum field theory.

The findings reveal that the holographic principle can be realized in flat spaces. This is particularly important to note when considering the physics of our universe.

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