Could our universe be just a hologram? This idea has been in people's minds before, and hardly anyone can be surprised by it, but nevertheless it seems so incredible that people do not take it seriously. However, it may well be a physical property of our world. And we may be about to see this.
Mathematicians are already familiar with the holographic principle, first proposed by the famous physicist Gerard t'Hooft and developed by the equally famous physicist Leonard Susskind. He argues that, firstly, all the information that is contained in a certain area of space can be represented as a hologram - a theory that "lives" on the border of this area. Like an observer-dependent gravitational horizon. Consequently, it requires one less dimension than it appears. More precisely, the theory at the boundaries should contain at most one degree of freedom per Planck square. More broadly, since the universe appears to be three-dimensional to us, it may actually be a two-dimensional structure superimposed on an incredibly large cosmic horizon.
Back in 1997, Juan Maldacena was the first to postulate a theory of the holographic universe, saying that gravity arises from thin vibrating strings that exist in ten dimensions. Since then, many physicists have been working in this direction.
“This work has culminated in the last decade and suggests that curiously, everything we experience is nothing more than a holographic projection of processes occurring on some distant surface that surrounds us,” wrote physicist Brian Green of Columbia University in 2011. “You can pinch yourself, and your sensation will be quite real, but it reflects a parallel process taking place in another, distant reality.”
Physicists at the Vienna University of Technology have suggested that the holographic principle works even in flat space-time, and not only in theoretical areas with negative curvature. As a rule, gravitational phenomena are described in three spatial dimensions, while quantum particles - only in two. It turns out that you can superimpose the results of some measurements on others - and this amazing conclusion has spawned more than 10,000 scientific papers in theoretical physics on the topic of negatively curved spaces. However, until now, it all seemed relatively far from our own, flat, positively curved universe.
“If quantum gravity in flat space allows a holographic description by standard quantum theory, then there must be physical quantities that can be calculated in both theories - and the results must be the same,” says Daniel Grumiller of the Vienna University of Technology. This includes the manifestation of quantum entanglement in gravitational theory, that is, particles cannot be described individually. It turns out that you can measure the amount of entanglement in a quantum system, this is called entanglement entropy. Grumiller shows that it has the same magnitude in flat quantum gravity and in two-dimensional field theory.
The scientist noted that this correspondence can be verified by the example of quantum entanglement, which manifests itself when the properties of objects, initially related to each other, turn out to be correlated even when they are separated by a distance from each other: a change in the properties of one object when moving away from others from the system affects the properties the rest.
“These calculations confirm our assumption that the holographic principle can take place in flat spaces. This is evidence for such a correspondence in our universe, says Max Riegler of the Vienna University of Technology.
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Sounds incredible. However, another step in favor of a holographic universe is scary.
Ilya Khel