Electromagnetic Wormhole...Cloaking

Envision This: Mathematicians Design Invisible Tunnel

Electromagnetic "wormhole" results from turning invisible sphere inside out

By JR Minkel  | May 4, 2007 | 0

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THE LIGHT at the end of the invisible tunnel. Researchers have cooked up blueprints for a "wormhole" that allows light to travel unseen from one point to another.Image: © ISTOCKPHOTO/GEORGE CAIRNS

Call it Harry Potter's invisible sleeve. New calculations show how to make an electromagnetic "wormhole"—a tube that is invisible from the sides, allowing light to shine down the center unseen [see endnote].

The concept is a twist on a spherical cloak of invisibility proposed last year. Such a device would be made of metamaterial, a thicket of metal rings or other shapes that bends light in funny ways. A hollow shell of metamaterial could in principle channel a single frequency of light around its inner space without slowing the light down, rendering that hidey-hole invisible to the outside world at that frequency.

But the invisibility cuts both ways. If light does not enter, then whatever is in the cloak cannot see outside, says mathematician Allan Greenleaf of the University of Rochester.

So Greenleaf turned the cloak inside out. In work submitted to a major physics journal, he and colleagues report that the light-warping trick works for an open tube with flared ends. Viewed straight on, light zipping down the cylinder would be plainly visible. But from the side, the light would appear to come out of nowhere, as though sent on a detour to another dimension and back.

The idea is the same as that of a wormhole linking two distant points in spacetime, hence the nickname. "We're tricking the electromagnetic waves … into thinking that, actually, space has been changed," Greenleaf says.

"It's a very nice twist" on the spherical cloak, says physicist John Pendry of Imperial College London, one of the physicists who first worked out the idea. "We can invent a secret connection between two parts of space, and that is interesting."

Building an invisible tunnel should be as hard—or easy, depending on your level of optimism—as making a spherical cloak, Greenleaf says. A Duke University team demonstrated an imperfect cloak last year that warps microwaves around a disk of concentric copper rings. But researchers are still struggling to build metamaterials that bend visible light.

Greenleaf's group speculates that wormholes could be used to pass metal objects into an MRI scanner or, by making a prickly sphere of them, create a 3-D video display. Of course, by the time invisibility becomes easy to achieve, modern technology will probably be a bit out of date.

Note: Parts of this article have been modified for clarity.

http://www.scientificamerican.com/article.cfm?id=envision-this-mathematicians-design-invisible-tunnel

Electromagnetic Wormhole's Possible.

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Not Just Science Fiction: 'Electromagnetic Wormhole' Possible, Say Mathematicians

ScienceDaily (Oct. 13, 2007) — The team of mathematicians that first created the mathematics behind the "invisibility cloak" announced by physicists last October has now shown that the same technology could be used to generate an "electromagnetic wormhole."

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In the study, which is to appear in the Oct. 12 issue of Physical Review Letters, Allan Greenleaf, professor of mathematics at the University of Rochester, and his coauthors lay out a variation on the theme of cloaking. Their results open the possibility of building a sort of invisible tunnel between two points in space.

"Imagine wrapping Harry Potter's invisibility cloak around a tube," says Greenleaf. "If the material is designed according to our specifications, you could pass an object into one end, watch it disappear as it traveled the length of the tunnel, and then see it reappear out the other end."

Current technology can create objects invisible only to microwave radiation, but the mathematical theory allows for the wormhole effect for electromagnetic waves of all frequencies. With this in mind, Greenleaf and his coauthors propose several possible applications. Endoscopic surgeries where the surgeon is guided by MRI imaging are problematical because the intense magnetic fields generated by the MRI scanner affect the surgeon's tools, and the tools can distort the MRI images. Greenleaf says, however, that passing the tools through an EM wormhole could effectively hide them from the fields, allowing only their tips to be "visible" at work.

To create cloaking technology, Greenleaf and his collaborators use theoretical mathematics to design a device to guide the electromagnetic waves in a useful way. Researchers could then use these blueprints to create layers of specially engineered, light-bending, composite materials called metamaterials.

Last year, David R. Smith, professor of electrical and computer engineering at Duke's Pratt School, and his coauthors engineered an invisibility device as a disk, which allowed microwaves to pass around it. Greenleaf and his coauthors have now employed more elaborate geometry to specify exactly what properties are demanded of a wormhole's metamaterial in order to create the "invisible tunnel" effect. They also calculated what additional optical effects would occur if the inside of the wormhole was coated with a variety of hypothetical metamaterials.

Assuming that your vision was limited to the few frequencies at which the wormhole operates, looking in one end, you'd see a distorted view out the other end, according the simulations by Greenleaf and his coauthors. Depending on the length of the tube and how often the light bounced around inside, you might see just a fisheye view out the other end, or you might see an Escher-like jumble.

Greenleaf and his coauthors speculated on one use of the electromagnetic wormhole that sounds like something out of science fiction. If the metamaterials making up the tube were able to bend all wavelengths of visible light, they could be used to make a 3D television display. Imagine thousands of thin wormholes sticking up out of a box like a tuft of long grass in a vase. The wormholes themselves would be invisible, but their ends could transmit light carried up from below. It would be as if thousands of pixels were simply floating in the air.

But that idea, Greenleaf concedes, is a very long way off. Even though the mathematics now says that it's possible, it's up to engineers to apply these results to create a working prototype.

Greenleaf's coauthors are Matti Lassas, professor of mathematics at the Helsinki University of Technology; Yaroslav Kurylev, professor of mathematics at the University College, London; and Gunther Uhlmann, Walker Family Endowed Professor of Mathematics at the University of Washington.

http://www.sciencedaily.com/releases/2007/10/071012160144.htm

Wormhole In Australia?