Researchers Crack the Code of Flying Doughnuts

November 18, 2018

Scientists have figured out how to make doughnut-shaped pulses of light. And, no, you can’t eat them – but it’s a big deal for at least three other reasons.

“Doughnut-shaped pulses of light” is a fun phrase to write and think about.
Donut-shaped pulses could help scientists probe the strange donut-shaped magnetosphere in certain kinds of matter.
For the first time, scientists may be able to create waves with what physicists call “space- and time-dependent functions.”
One of the theorists behind the discovery, Nikitas Papasimakis, a physicist at the University of Southampton, says that each of the created electromagnetic waves can be described by an equation if we know where it is in time or space.

For example, an electromagnetic pulse shaped like a sine wave, like the one illustrated below, looks about the same 5 seconds after it appears and 30 seconds after it appears (or, for that matter, 5 or 30 feet from where it appears). To describe it, you just need to know where it is in time or space.

“Flying saucers” are also waves, and they’re part of a special, theoretical class of waves first proposed in 1996 (which also includes something called “focused pancakes”) that are so strange and complex that, in order to work, the equations describing them require knowing where the wave is in space and time, Papasimakis told Live Science.

If scientists produced a flying pancake in the real world, it would be the first time humans have created such a complex wave.

In addition to bragging, there is a more practical reason scientists want to create these waves, Papasimakis said, so they can begin to understand a strange behavior sometimes seen in matter.

In fact, a lot of Papasimakis’ recent work has focused on this strange behavior of matter. In some cases, matter can be excited by electromagnetism. Scientists have a good understanding of the more common versions of this effect, such as the ends of the magnets you stick on your refrigerator. But there’s a less common version, called “toroidal magnetic excitation” – basically a donut-shaped region of magnetic excitation in a chunk of matter – which is governed by physics that scientists are still figuring out.

Papasimakis says it’s not well studied – in part because the effect is so weak.

Flying doughnuts could help researchers probe these ring excitations, he said.

To generate a flying donut, scientists would need to build a special material that is essentially a series of carefully placed antennas, according to a paper published May 23 by Papasimakis and his colleagues in Physical Review B. These antennas could come in different sizes and distances, depending on how big a donut you’re trying to generate, he added.

The next step, he said, is to actually build one of these arrays and launch a flying doughnut in real life. He said he and his colleagues are already working on it.