Noronha and Noronha-Hostler awarded $1.375M to study quark-gluon plasmas

Researchers at the University of Illinois Urbana-Champaign have been awarded a $1.375 million grant to develop theoretical and computational tools for studying the quark-gluon plasma, a state of matter that exists in the most extreme conditions in the universe.

The research, co-led by Illinois Physics Professors Jorge Noronha and Jacquelyn Noronha-Hostler, will result in both mathematical models and simulation techniques to study quark-gluon plasmas. The results can be used to understand the Big Bang, extreme astronomical events like neutron star mergers, and even particle collider experiments here on Earth.

“Although quark-gluon plasmas impact several distinct areas of physics, the tools to understand them are still under development,” Noronha says. “If we succeed, we’ll have mathematical equations that are consistent with experiments and algorithms to simulate the plasma’s behavior under a variety of conditions.”

Quark-gluon plasmas are created when atomic nuclei are collided at very high energies, which heats them to very high temperatures. Under these conditions, the protons and neutrons comprising the nuclei break into smaller particles called quarks and gluons and form a kind of plasma, a state of matter in which charges are free to move throughout.

Physicists believe that such a plasma pervaded the universe in the microseconds after the Big Bang, and that a colder and much denser version may form in collisions of neutron stars – remnants of ordinary stars after they exhaust their fuel and explode in supernovae.

Particle collider experiments have allowed quark-gluon plasmas to be created in laboratory conditions, but they have displayed surprising properties that current theories are not equipped to handle.

“Quarks and gluons in protons and neutrons experience something called confinement,” Noronha-Hostler explains. “It’s like they’re caught in a finger trap toy: they’re free to move around if they’re close together, but, if you try to pull them apart, the trap squeezes and they become basically impossible to separate. For this reason, one might expect that quarks and gluons in plasmas don’t interact very often.

“But experiments have found that the quarks and gluons interact very strongly. We initially expected something like a gas, but what we see is closer to a liquid.”

The realization that quark-gluon plasmas are strongly interacting, and display fluid-like properties like viscosity, has prompted intensified theoretical research to describe their large-scale behavior. It is necessary to develop new mathematics extending accepted theories of fluid mechanics.

“Quark-gluon plasmas that form in laboratory conditions flow at speeds close to the speed of light,” Noronha adds. “So, the equations governing that flow need to respect Einstein’s theory of special relativity and prevent the flow from going faster than light. This turned out to be a very challenging problem that is still an active area of research after decades of work.”

The researchers will study the problem from two perspectives. Noronha will formulate fluid equations that respect constraints imposed by special relativity and agree with experimental observations, while Noronha-Hostler will develop numerical algorithms to simulate these equations on a computer.

According to the researchers, these tools will find applications in multiple areas of physics. An understanding of fluids flowing close to the speed of light is needed to model colliding neutron stars and calculate the resulting gravitational waves that can be detected. In addition, the techniques may provide insights into a recently launched experiment to study quark-gluon plasmas, sPHENIX at Brookhaven National Laboratory.

The award, DE-SC0023861, will be distributed by the U.S. Department of Energy Office of Science over five years.