AN EXOTIC type of quantum matter could help test fundamental theories of nature, such as string theory, that are beyond the reach of today鈥檚 experiments.
So say Don Colladay and Patrick McDonald at the New College of Florida, who have examined how any deviations from Einstein鈥檚 theory of relativity would be reflected in Bose-Einstein condensates. These 鈥渟uper-atoms鈥� form when quantum particles with the same energy clump together at temperatures close to absolute zero.
Relativity is one of the foundations of modern physics. At its heart lies the assumption that the laws of physics are the same for everyone, everywhere in the universe, regardless of how fast they move or which direction they face, a property known as Lorentz symmetry.
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Attempts to reconcile gravity with quantum physics in a theory of everything have led to suggestions that this symmetry may not hold for more fundamental theories that underlie current models of the universe. In string theory, for example, particles can be thought of as strings that exist within sheet-like branes in extra dimensions. That may set up preferred directions in space-time, something that is forbidden by Lorentz symmetry.
One way this anomaly may manifest itself is in the behaviour of particles at the smallest scale. But how to detect this?
The team think that these aberrations will register in the super-atoms that are Bose-Einstein condensates. If relativity is violated, this would cause small but measurable changes to properties of the super-atom鈥檚 quantum state, such as its shape. The presence of large numbers of particles occupying the same quantum state can magnify otherwise unobservable effects, Colladay says.
鈥淎ny experimental evidence would be dramatic because it would provide a glimpse of physics at the deepest level,鈥� says Alan Kostelecky at Indiana University in Bloomington, who first suggested Lorentz violations could arise in string theory.
Scott Dodelson at Fermilab in Illinois, is more cautious. 鈥淭here have been several tests to date, and Lorentz invariance has passed all with flying colours,鈥� he says. 鈥淭heir idea seems right, but experimentally challenging.鈥�
