Cover illustration by Anders Sandberg

This artist’s impression represents a view of a hyperbolic plane — the kind of beast that M. C. Escher loved to paint — projected on the surface of a sphere. Maldacena’s concept of the holographic universe translates a string theory living in hyperbolic space (the 3-D analogue of hyperbolic plane) into a theory of particles living on the surface of a sphere.

In a school of thought that teaches the existence of extra dimensions, Juan Maldacena may at first sound a little out of place.

String theory is physicists’ still-tentative strategy for reconciling Einstein’s theory of gravitation with quantum physics. Its premise is that the subatomic particles that roam our three-dimensional world are really infinitesimally thin strings vibrating in nine dimensions. According to Maldacena, however, the key to understanding string theory is not to add more dimensions but to cut their number down.

In his vision, the mathematical machinery of strings completely translates into a more ordinary quantum theory of particles, but one whose particles would live in a universe without gravity. Gravity would be replaced by forces similar to the nuclear forces that prevailed in the universe’s first instants. And this would be a universe with fewer dimensions than the realm inhabited by strings.

Just as a hologram creates the illusion of the third dimension by scattering light off a 2-D surface, gravity and the however many dimensions of space could be a higher-dimensional projection of a drama playing out in a flatter world.

How many dimensions space has could all be a matter of perspective.

(This article checks out the state of Maldacena’s conjecture ten years after he first proposed it, in November 1997. Read the rest of it on the Science News web site)

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