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When we watch the movies of Harry Potter, the cloak he wears to become instantaneously invisible makes his movies not only fascinating but "way-out there" for the majority of viewers. But researchers are developing what we pay to see at the Potter movies---the cloak of invisibility which involves an object becoming invisible or undetectable to electromagnetic waves.  The article entitled, "Cloaking Devices, Electromagnetic Wormholes, and Transformation Optics" , by Allan Greenleaf and colleagues was recently published in the SIAM Review for March, 2009, presenting the overview of invisible cloaking from a mathematical perspective---focusing on its theoretical developments. The process of mathematics is extremely important when creating metamaterials to show that the material involved actually ensures invisibility.

Metamaterials are manmade artificial structures or devices. Definitely not considered a new concept, it involves its physical structure instead of chemical make-up. But they have been applied as cloaking devices needing to be undetectable to electromagnetic waves in order for an "invisible region" to remain unseen.  The whole idea involves light waves bending around a particular object or region---emerging on the other side as if the waves had passed through an empty space.  The process would not work if the microscopic surface was not smaller than that of the wave length of the light being used.

The 1860 Scottish mathematician and physicist James Maxwell was responsible for the study of equations for electromagnetic waves. Unfortunately, the transformations which define the parameters of the required material have points where the parameters fail to have properties or to exist—properties consisting of smoothness or boundness which are needed to demonstrate the cloaking process.

The future holds great promises for cloaking via the electromagnetic wormholes: invisible fiber optic cables, security devises, MRI-assisted medical procedures, and three-dimensional television screens---but are totally dependent on future developments in metamaterial design, production and investigation. Different from what we recognize as traditional wormholes---where theoretically there is a bend in space and time, serving as a shortcut for vast distance traveling---electromagnetic wormholes allow objects traveling through it to become invisible.

The electromagnetic wormholes allow an object to remain invisible until it would emerge from the other side, remaining invisible until then. The inside tunnel would be coated with metamaterials, presently considered an experimental class of artificial substances.  Unlimited in its size, the tunnel or cylinder will be able to render an exact range of frequencies to render the object invisible. The results from Greenleaf's experiment will be published in the October 26, 2009 "Physical Review Letters".

"It would create a complete a disconnection between the outside world and stuff inside the cloaking region. It's good for hiding things," said mathematician Allan Greenleaf of the University of Rochester.