The universe may be a hologram, according to a new mathematical model developed at the Vienna University of Technology (TU Wien). If this is true, it means we could all be living our lives in just two spatial dimensions, rather than the familiar three of length, width and height.

The holographic principle positing that our universe may contain just two dimensions of length was first proposed in 1997, exciting theoretical physicists. What we perceive as a third dimension could in fact be two-dimensional events on the "horizon" of a two-dimensional image. This property of the universe would behave much like the holograms used on credit cards —  in spite of being two-dimensional, they create an illusion of depth.

This astounding idea has only been studied mathematically, in cases in which the universe is said to possess a negative curvature — similar to a horse saddle. New calculations show that a two-dimensional universe projecting a holographic appearance of three dimensions could also take place if spacetime were flat.

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

Pairs of entangled quantum particles cannot be described mathematically as separate objects, regardless of the distance between them. The entropy of entanglement – a measure of the degree of entanglement in a given quantum system – was found to be identical in theories of gravity and quantum mechanics in a universe possessing just two dimensions.

Theories of quantum effects, calculated in two dimensions, may thus be "mapped" onto gravitational models designed in three dimensions. This idea is so odd, it's comparable to finding that the instruction manual for a dishwasher holds the recipe to making a good chocolate souffle.

"This calculation affirms our assumption that the holographic principle can also be realized in flat spaces. It is evidence for the validity of this correspondence in our universe," Grumiller said. "The fact that we can even talk about quantum information and entropy of entanglement in a theory of gravity is astounding in itself, and would hardly have been imaginable only a few years back."

Flatland: A Romance of Many Dimensions is a satirical novel by Edwin Abbott Abbott published in 1884 that explored life in a two-dimensional universe. Now, that book may prove to be prophetic. Although this new finding in theoretical physics doesn't prove that we're living in a holographic universe, it does provide more evidence for the two-decade old idea.

Analysis of the possibility of the universe as a two-dimensional hologram was detailed in the journal Physical Review Letters.

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