Superfluids could create a 'universe in a bucket'

• 14 February 2008
• From New Scientist Print Edition. Subscribe and get 4 free issues.
• Zeeya Merali

IT'S an ambitious task, recreating the universe in a bucket. But if it is successful, the experiment could help solve the twin puzzles of why we're made of matter rather than antimatter and where the huge magnetic fields that span galaxies come from.

At last month's Cosmology Meets Condensed Matter conference in London, it emerged that space-time could be simulated in the lab using weird substances known as "superfluids", which flow without resistance and can even climb up the walls of jars. Intriguingly, the equations governing the particles inside superfluids are similar to those that represent the early universe, says Ray Rivers at Imperial College London. "We hope that we can use these to check things in the lab that frankly we don't have any hope of seeing through astrophysical observations."

Tanmay Vachaspati at Princeton University thinks that studying superfluid helium-3 could help solve two mysteries: why the universe is made almost entirely of matter rather than antimatter and the seemingly inexplicable origin of the magnetic fields that thread through galaxies.

Cosmologists believe that equal amounts of matter and antimatter should have been created in the early universe. But since matter and antimatter annihilate each other, something must have happened to create an excess of matter, leading to the universe we see today. Some of the antimatter could have been converted to matter through a process involving virtual particles, which momentarily pop out of the vacuum before disappearing again, says Vachaspati. Among these would have been magnetic monopoles - hypothetical particles carrying a single magnetic charge. As the monopoles disappear, they force nearby antimatter to become matter.

The monopoles, says Vachaspati, could also leave behind a trace: twisted magnetic field lines. These lines would have been stretched out as the universe expanded, giving rise to galactic magnetic fields.

These traces in the early universe would be hard to spot in the cosmic microwave background left behind by the big bang, but superfluid helium-3 could provide a way to test the idea, Vachaspati says: spin a container of the stuff, and you create vortices whose edges share similar dynamics to monopoles, including their disappearing act. This means that the twisted field lines would be visible in the arrangement of superfluid particles left when the vortices disappear. "I really want to encourage experimentalists to look for this," he says.

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