Science News - October 23, 2010

Smolyaninov suggests a solution online at arXiv.org and in an upcoming Journal of Optics. Metamaterials, he claims, can be made to mimic the multiverse. He says the idea is straightforward: Pockets with different properties could be designed to replicate adjacent universes. The pockets could be created so light can’t escape — as in the black hole scenario— or so that light can move among them.

And just as some physicists believe that some dimensions of the visible universe could be compactified —shrunk down really small —the same could be emulated for dimensions in other universes. One pocket universe with two compactified and two extended dimensions could sit next to a space with three compactified dimensions and one extended dimension, for example.

Analog systems have been beneficial to theorists over and over again, says metamaterials expert Ulf Leonhardt of the University of St. Andrews in Scotland. He suspects that something could be gleaned from this system too. “In some areas of theoretical astrophysics, people are just relying on theory,” he says. “They have been relying on theory for a very long time.”

The idea that space can have compactified dimensions has been around for a while. In the 1920s, Polish mathematician and physicist Theodor Kaluza proposed that an extra dimension might exist beyond the three of space and one of time that are typically experienced. Soon after, Swedish physicist Oskar Klein proposed that such an additional dimension of space could be wrapped up into a small loop. Because it would be too tiny to see, the dimension wouldn’t be like those that people know and love, the ones that allow moving forward or back, up or down and side-to-side. Yet particles would notice it. Adding the extra dimension did for electromagnetism what general relativity did for gravity —it gave the field a geometric underpinning.

A common way to think about a compactified dimension is to consider an ant walking along a garden hose. From far away, the garden hose appears

one-dimensional — the ant can move only along its length. But zoom in closer, and it becomes obvious that the ant can also loop around the hose’s circumference, so a second dimension is available. Just as this second dimension is hidden from a distant observer, an extra curled-up dimension may be hidden from people in the real world.

Smolyaninov calls the Kaluza-Klein idea “a stone of theoretical physics.” And although his original proposal for a metamaterial multiverse focused on universes with fewer dimensions, he reports online September

6 at arXiv.org that metamaterials could mimic a world with five or more dimensions. Simulating higher dimensional spaces could make the analogs more interesting to string theorists, who propose the existence of many dimensions too small to see.

In the materials that Smolyaninov dreams of creating, photons can occupy an infinite number of quantum states. Some type of change, in temperature perhaps, could make the unusual material — if constructed just right — revert to a state in which photons can’t occupy so many positions. When this transformation happens, the particles have to be emitted, like a bunch of kids getting kicked out of a game of musical chairs all at once. Those emitted photons would create a flash of light.

“It looks like a Big Bang situation,” Smolyaninov says. Such a flash could emulate the birth of the universe.

And the flash could be made in a sec-
ond way, Smolyaninov argues. Consider
the dimensions that people experience
(leaving Kaluza-Klein out of the picture
for now). There are three of space and
one of time; the time dimension behaves
differently, so it gets its own special math
to describe it. But when what’s called a
metric signature change occurs, a time-
like dimension can take on spacelike
qualities, or vice versa. Metamaterials
could also replicate the math behind this
type of transformation, Smolyaninov
and Evgenii Narimanov of Purdue Uni-
versity in West Lafayette, Ind., propose
in the Aug. 6 Physical Review Letters.