A Brown physicist is creating waves around the world with his paper asserting that researchers at Brookhaven National Laboratory in Stony Brook, N.Y., made a fireball that acts like a black hole. However, it only acts like a black hole in what Horatiu Nastase, assistant professor of physics (research) and author of the paper, calls "imaginary space."
The type of fireball in question is made by a relativistic heavy ion collider, or RHIC, an instrument that creates collisions between particles at high speeds. In this case, two beams of gold nuclei hit head-on. Sometimes when this is done, the physicists observe "a ball of matter that explodes by emitting thousands and thousands of particles," Nastase said. It lasts for 10 million trillionths of a millisecond.
The theory which describes matter at energies as high as those of the fireball is called quantum chromodynamics. It is very complicated and rarely offers quantitative predictions for the real world. However, in the last seven years, physicists have found a way to create links between QCD and string theory.
"String theory is an attempt to unify all the particles and forces in nature," Nastase said. According to this theory, all particles - such as electrons, protons and photons - are actually strings that vibrate in different ways. In the same way that different vibrations of violin strings give different notes, different vibrations of these strings create different particles.
This fireball's only relationship with a black hole exists on paper, in Nastase's calculations, which link the real world to an "imaginary" 10-dimensional world described by string theory. "This is just a mathematical equality," Nastase explained. The similarity between real black holes in our universe and the one described in the imaginary world is that they both absorb particles and give out thermal radiation, he said.
"This is not really a black hole in our common understanding," said Greg Landsberg, associate professor of physics. In fact, several years ago, a study at RHIC determined whether the collider could produce something dangerous, such as a black hole. According to Landsberg, researchers concluded that creating a black hole requires much higher energies than RHIC can produce.
Sensationalist news headlines, such as the BBC's "Lab fireball 'may be black hole,'" have prompted public interest in the topic. Several radio programs and publications, including the New York Times, have featured Nastase's research.
In the world of physics, the research has also created quite a splash. The paper is currently published in an online database and has yet to be peer-reviewed, but many researchers in the field of high-energy physics have expressed cautious interest. Nastase said this application of string theory is the first to describe findings from real experiments.
Chung-I Tan, professor and chair of the Department of Physics, said of the research, "It's very exciting, but it's unclear whether the theoretical actually applies to the experiments at RHIC."
Professor of Physics Antal Jevicki said many people in his field are interested in black holes, but no one has yet created them. "The next best thing is some object analogous to black holes," he said. If Nastase's findings hold up, the fireball could be used for further studies of black holes.
"In terms of some meaning for the point of view of our world, we don't know," Landsberg said. "It's a bit too early to say anything."
Landsberg has expressed interest in using a higher-energy collider at CERN in Geneva to create a real black hole in the laboratory. He said, however, that like the fireball, any black hole created by a collider would exist for such a short time it could do no damage.
This type of black hole could be produced daily by cosmic rays entering the earth's atmosphere. "They're an organic type of black hole. They're very good - you can eat them with your salad," Landsberg said.
