09:30 09 October 04
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The theory that claims to solve cosmology’s major mysteries by proposing that empty space is filled with a fluid of ghostly particles may, literally, be going down the cosmic drain. According to the latest calculations, the universe’s black holes would be slurping up any such fluid.
The ghost condensate theory, proposed last year, is a modified form of Einstein’s general theory of relativity. It posits an all-pervading fluid of massless particles that exhibits a repulsive gravity, making it behave like an elastic band that stores more and more energy as it stretches out.
The theory’s attraction for cosmologists is that it promises to explain at a stroke three of their most pressing conundrums: the nature of the dark energy that is pushing the universe apart, the nature of the dark matter that holds spinning galaxies together, and what it was that caused the universe to undergo a rapid inflation just after the Big Bang (New Scientist print edition, 7 February, 2004).
But Andrei Frolov of Stanford University, California, wondered what would happen if the ghost condensate came in contact with a black hole, as it must if it pervades the universe. His calculations show, ironically, that the repulsive gravity that makes the ghostly fluid so alluring to cosmologists also makes it unable to resist the pull of black holes. “It’s going to be falling pretty much like dust would fall into a black hole,” Frolov says.
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Andrei Frolov, Stanford University
Markus Luty, University of Maryland
Physical Review D
A black hole with the mass of our Sun would pull in the fluid at a rate of 1/10th of the Sun’s mass every second, he found. At this rate, the supermassive black holes at the centre of galaxies like the Milky Way should be about twice as large as they actually are. “It’s observationally clear this isn’t happening,” Frolov says.
But the proponents of the theory, including Markus Luty of the University of Maryland in Baltimore, are not convinced. They say the ghost condensate should respond very slowly to cosmic events such as the formation of black holes, whereas Frolov assumes that the ghost particles everywhere would have felt the gravitational influence of such events long ago.
According to Luty, ghost condensate that is far away from a black hole will be oblivious to it for billions of years, and hence will not have been sucked in at the rate claimed by Frolov. More detailed calculations should resolve the debate.
Journal reference: Physical Review D (vol 70, p 61501)