Exploding black holes could expose hidden dimensions

18:48 05 February 2008
NewScientist.com news service
Ker Than

Cosmic flares shot from exploding black holes could provide long-sought proof of extra spatial dimensions, new calculations suggest.

Theoretical physicist Stephen Hawking predicted that black holes evaporate through a quantum process known as "Hawking evaporation" and can explode in brief bursts of energy before vanishing completely.

Only mini-black holes roughly as massive as an asteroid or smaller would be able to evaporate completely within the lifetime of the universe. And such tiny black holes may have been created in large numbers within 1 second of the big bang, as elementary particles clumped together at extreme energies.

Now, researchers led by Michael Kavic of Virginia Tech in Blacksburg, US, say the evaporation of such "primordial" black holes could emit detectable radiation – if the universe contains additional dimensions beyond the familiar three of space and one of time. Such extra dimensions are predicted in some theories that try to unify gravity and quantum mechanics, such as string theory.

In the presence of extra dimensions, black holes would wrap around these extra dimensions to form "black strings." "You can envision this as a rubber band wrapped around a fire hose," Kavic told New Scientist. "As the black hole evaporates, it eventually becomes too small to wrap the extra dimension."

Unique pulse

He and colleagues predict that when a black string snaps, it will expose the extra dimension by creating a pulse of radiation with a unique electromagnetic signature. "We would know them if we saw them," Kavic told New Scientist.

By analysing the frequency of the pulse, scientists could calculate the size of the extra dimension, which could lend insight into which cosmological model best describes the universe. "The size of the black string is directly related to the size of the extra dimension at the time of the explosion," Kavic says.

The team says the light pulses could be detected by radio telescopes capable of scanning the entire sky in one sweep, such as Virginia Tech's Eight-meter-wavelength Transient Array.

"Traditional radio telescopes only focus on a very small part of the sky at any one time," Kavic said. "This means that they could easily have missed these kinds of pulses."

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