Early universe was ‘perfect’ fluid

Scientists using a giant atom smasher said they have created a new state of matter – a hot, dense liquid made out of basic atomic particles – and said it shows what the early universe looked like for a very, very brief time.

For a tiny fraction of a second after the "big bang" birth of the universe, all matter was in the form of this liquid, called a quark-gluon plasma, the researchers said. "We have a new state of matter," said Sam Aronson, associate laboratory director for High Energy and Nuclear Physics at the Brookhaven National Laboratory.

"We think we are looking at a phenomenon ... in the universe 13 billion years ago when free quarks and gluons ... cooled down to the particles that we know today," Aronson told a news conference carried by telephone from a meeting of the American Physical Society in Tampa, Florida.

The quark-gluon plasma was made in the Relativistic Heavy Ion Collider – a powerful atom smasher at Brookhaven National Laboratory in Upton, New York. Unexpectedly, the quark gluon plasma behaved like a perfect liquid of quarks, instead of a gas, the physicists said.

For their experiment, the researchers smashed two gold ions together at extremely high speeds, very close to the speed of light. The collision was so intense that the strong force that usually binds quarks into protons and neutrons weakened, allowing the quarks to roam freely.

Normally quarks, the most basic particles that make up matter, are bound together and cannot be measured directly. At temperatures 10,000 times hotter than those found inside the sun and with just a few thousand particles, the nuclear physicists expected the quarks to fly around freely like a gas.

Instead, the quarks behaved like a perfect liquid, flowing together like a school of fish, without turbulence or random motion. In contrast, a drop of water containing the same number of particles would not behave like a liquid at all, but just fly apart. "This is fluid motion that is nearly 'perfect,'" said Aronson. "The truly stunning finding at RHIC that the new state of matter created in the collisions of gold ions is more like a liquid than a gas gives us a profound insight into the earliest moments of the universe," said Raymond Orbach, Director of the Department of Energy Office of Science, which funds the collider.

The unexpected results have a link to another field of physics, called string theory. String theory attempts to explain properties of the universe using 10 dimensions, instead of the three space and one time dimension that humans commonly perceive.

The string theory calculation describing how gravity behaves near a black hole can also explain how quarks move in a quark gluon plasma, experts said. "It's very powerful, very intriguing," said Miklos Gyulassy, a theoretical nuclear physicist at Columbia University in New York. The findings, detialed in four separate studies, will be published in the journal Nuclear Physics A. reuters

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