Mathematical cloaks

University of Utah mathematicians have developed a new cloaking method that someday might shield submarines from sonar or planes from radar.

’We have shown that it is numerically possible to cloak objects of any shape that lie outside the cloaking devices, not just from single-frequency waves, but from actual pulses generated by a multi-frequency source,’ said Graeme Milton, a distinguished professor of mathematics at the University of Utah.

Although the new cloaking method has only been simulated to work in two dimensions, Prof Milton believes it can be extended easily to three dimensions, meaning real objects could be cloaked.

In use, the new active cloaking method would shield devices that actively generate electromagnetic fields rather than being composed of ’metamaterials’ [exotic metallic substances] that passively shield objects from passing electromagnetic waves.

Milton said his previous research involved just cloaking clusters of small particles, but added that his team are now able to cloak larger objects.

For example, radar microwaves have wavelengths of about four inches, so Milton said the method could be employed to cloak an object 10 times wider, or 40 inches from radar. That raises hope for cloaking larger objects.

A study demonstrating the mathematical feasibility of the new cloaking technique - active, broadband, exterior cloaking - was published online in the journal Optics Express. A related paper was published online on 14 August in Physical Review Letters.

The new studies are numerical and theoretical, and show how the cloaking method can work. ’The research simulates on a computer what you should see in an experiment,’ Milton said.

A video showing an object uncloaked and cloaked as a wave passes may be seen and downloaded from http://vimeo.com/6092319 or as separate videos from http://vimeo.com/5406253 (no cloaking) and http://vimeo.com/5406236 (with cloaking).

These images are from animated computer simulations of a new method for cloaking objects from waves of all sorts. The top three images show a wave front passing the kite-shaped object in the middle and hitting the object as it does. In the bottom three images, the kite-shaped object is surrounded by three cloaking devices and the waves they emit. So when the wave front passes, it moves by the object without touching it