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Are we living in a hologram? Recent attempts to turn string theory into a workable theory of nature have led to this potential conclusion. Believe it or not, what we perceive as three spatial dimensions could actually be composed of only two. It sounds far-fetched, but the greatest realization of the hologram-led success is a thing called the AdS/CFT correspondence, proposed by string theorist Juan Maldacena in the late 1990s.
The AdS/CFT correspondence is not a solution to the problems posed by string theory per se—they are still unsolved mysteries— but a statement motivated by advances in the theory. And it tells us an exciting idea—that we live in a hologram, igniting our curiosity for what that revelation might entail.
Let’s unpack these acronyms briefly to see how powerful this connection is and what it can teach us. The “AdS” refers to anti-de Sitter, which is a particular kind of solution to Einstein’s general theory of relativity. It was not intended to describe the real universe, but was aimed to simplify Einstein’s equations enough to become approachable. The “anti” in “AdS” refers to another mock universe that is also entirely empty, with inward curvature.
The “CFT” in the correspondence refers to conformal field theory, a specific kind of quantum theory construction. Maldacena’s insight was that a certain version of string theory in an anti-de Sitter universe can map onto a conformal field theory on the surface of that universe. What does that mean? It means that Maldacena found that he could solve the intractable problem of quantum gravity within a universe by mapping it onto the surface of that universe, where gravity goes away and is replaced by a set of physics that we know how to solve.