The strange cosmic paradoxes, that Princeton quantum physicist John Archibald Wheeler coined “black holes,” have no memory, yet are said to contain the earliest memories of the universe, as well as the most recent, while at the same time obliterating all memory by obliterating all its manifestations. And yet, like a hologram, they have two dimensions, in which gravity disappears, but they reproduce an object in three dimensions, aligning with Einstein’s theory of relativity, which describes black holes as three dimensional, simple, spherical, and smooth, as they appear in the famous image of the black hole in M87 captured by the Event Horizon Telescope in April 2019.
Black Holes as Holograms –“Most complex existing systems”
According to new research black holes could be like a hologram, where all the information is amassed in a two-dimensional surface able to reproduce a three-dimensional image. In this way, these cosmic bodies, as affirmed by quantum theories, could be incredibly complex and concentrate an enormous amount of information inside themselves, as the largest hard disk that exists in nature, in two dimensions.
For scientists, black holes are a big question mark for many reasons. They are, for example, excellent representatives of the great difficulties of theoretical physics in putting together the principles of Einstein’s general theory of relativity with those of quantum physics when it comes to gravity. According to the first theory, they would be simple bodies without information. According to the other, as claimed by Jacob Bekenstein and Stephen Hawking, they would be “the most complex existing systems” because they would be characterized by an enormous “entropy”, which measures the complexity of a system, and consequently would have a lot of information inside them.
To study black holes, the two authors of the research, physicists Francesco Benini at the Institute for Advanced Study, and Paolo Milan with SISSA, used an idea almost 30 years old, but still surprising, called the “holographic principle”.
“This revolutionary and somewhat counterintuitive principle proposes that the behavior of gravity in a given region of space can alternatively be described in terms of a different system, which lives only along the edge of that region and therefore in a one less dimension,” say the duo. “And, more importantly, in this alternative description (called holographic) gravity does not appear explicitly. In other words, the holographic principle allows us to describe gravity using a language that does not contain gravity, thus avoiding friction with quantum mechanics”.
The Quantum Theory
What Benini and Milan have done “is apply the theory of the holographic principle to black holes. In this way, their mysterious thermodynamic properties have become more understandable: focusing on predicting that these bodies have a great entropy and observing them in terms of quantum mechanics, you can describe them just like a hologram: they have two dimensions, in which gravity disappears, but they reproduce an object in three dimensions”.
Testing Predictions About Quantum Gravity
“This study,” explain the two scientists, “is only the first step towards a deeper understanding of these cosmic bodies and of the properties that characterize them when quantum mechanics crosses with general relativity.”
In the near future, we may be able to test our theoretical predictions regarding quantum gravity, such as those made in this study, by observation. And this, from a scientific point of view, would be something absolutely exceptional”.
The study which demonstrates it, and which unites two discordant theories, has recently been published in Physical Review X.
The Daily Galaxy, Max Goldberg, via SISSA
Image credits: Event Horizon Telescope