Rice faculty win two MURI awards

Hulet, Dueñas-Osorio win Defense Department funding for basic research

Two Rice University research teams have won multiyear grants for basic research through the Department of Defense’s Multidisciplinary University Research Initiative (MURI) Program.

Researchers in the laboratory of physicist Randy Hulet will use lasers to snare and study ultracold lithium atoms in one- and two-dimensional optical traps in an effort to better understand nonequilibrium dynamics. Across campus, the research group of Engineering’s Leonardo Dueñas-Osorio will look for ways to control the interconnected “uber-networks” of gas, water, power and other utilities that are the backbone of modern society.

The grants will bring about $1.6 million in funding to Rice over five years, and despite their dissimilarities, the two research programs have the identical aim of making a fundamental breakthrough in a subject of extraordinary complexity.

Researchers in the laboratory of Rice physicist Randy Hulet will use lasers to snare and study atoms in optical traps in an effort to better understand nonequilibrium dynamics.

Hulet’s group is part of team that includes nine research groups at the University of Chicago, the Massachusetts Institute of Technology, Ohio State University, Cornell University and Harvard University. The team is led by Chicago’s Cheng Chin.

“Dynamics refers to how particles respond to forces, and nonequilibrium refers to the thermal state of a system,” said Hulet, the Fayez Sarofim Professor of Physics and Astronomy. “For example, if I have a bar of metal and I heat one end of the bar, that’s a nonequilibrium situation. As the bar is heated the temperature difference between the two ends will produce forces that cause the heat to flow from one end to the other.”

That level of understanding is sufficient for explaining things at a macroscopic scale — like how hot a particular gauge of wire will become under a specific operating voltage or how much heat an air-conditioning system can remove from a certain volume of air in a given length of time. What physicists don’t yet understand is how those larger, macroscopic changes are created at the microscopic level of atoms and electrons.

“We want to understand how the particles move to attain equilibrium,” Hulet said. “What are the time scales? What are the processes? How does the approach to equilibrium depend on whether the system is a one-dimensional wire or a three-dimensional object, or if the particles interact weakly or strongly with one another? What if the material is a superconductor? Many technologies depend on transport of energy, electricity, heat, fluid, even information. So the answers to these questions are important for application, as well as to basic science.”

Hulet’s experimental apparatus provides his team an extraordinary level of control. Using a combination of laser beams, the researchers in his lab can trap, hold and cool tiny clouds of lithium atoms to within a few billionths of a degree above absolute zero. At such cold temperatures, the quantum forces acting upon the atoms become more apparent.

In one experiment for the project, Hulet’s team will use multiple lasers to confine a string of ultracold atoms end to end in a narrow passage where they can move only in one dimension. By introducing a quantum disturbance at one end of the passage — like adding heat to the end of the metal bar — Hulet’s team can observe each atom as the disturbance propagates down the passage. In a second experiment, the team will attempt to recreate a phenomenon known as “jet suppression,” which has been observed in quark-gluon plasmas inside atomic accelerators.

“The quark-gluon plasma is so hot that it last existed in nature just a brief moment after the Big Bang,” Hulet said. “In contrast, the temperatures of our experiments are colder than anything in the deepest regions of interstellar space. The ratio between the two energy scales is 10 to the 21st power, or a 10 with 21 zeros after it. You’d think these two have little in common, but the two systems exhibit an almost perfect fluidity that is remarkably similar. It’s an incredible connection, and we’re trying to explore how far it goes.”

Dueñas-Osorio’s research is part of an interinstitutional effort aimed at not only understanding the behavior of interconnected networks but also at learning new ways to control that behavior.

Engineering's Leonardo Dueñas-Osorio, seen here inspecting damage from the 2010 Chile earthquake, will look for ways to use network interdependencies to control coupled utility networks.

The project, which is led by the University of California at Davis’ Raissa D’Souza, involves research groups at the University of Wisconsin, the University of Washington, the California Institute of Technology and Rice.

“The novelty of the proposed research is to utilize network interdependencies, which many see as a weakness in networked systems, to actually control such complex systems,” said Dueñas-Osorio, associate professor of civil and environmental engineering.

In previous work with D’Souza, Dueñas-Osorio and colleagues investigated how power grids, communications networks and other “lifeline systems” respond to natural disasters like 2012’s Hurricane Sandy and the 2010 Chile earthquake.

For the MURI research, the team will work to develop a fundamental theory for the control of coupled complex networks, regardless of their scale.

“We will be developing an entire subset of new mathematics, and that’s what makes it interesting,” Dueñas-Osorio said. “The way we represent networks today is through matrices, but for the problems that we are trying to handle, which is controlling coupled networks, that is just too limited.”

He said the group hopes to develop new mathematical descriptions, or “objects,” to accurately capture the complexity of coupled networks. These objects would allow the researchers to probe the interconnectedness within coupled networks in a way that hasn’t previously been possible, Dueñas-Osorio said.

“We hope to bridge the divide that typically exists between engineering, mathematics and complex systems,” he said. “The upshot is that these new objects will be more than mathematical abstractions. They’ll also be very practical because the engineering constraints of the networks will be embedded in the mathematical definition.”

Dueñas-Osorio said the team plans to test its new theory in applied systems ranging from coupled nanoelectromechanical oscillators to interdependent infrastructure systems and coupled primate societies.

At Rice, Dueñas-Osorio’s team will lead the portion of the study that examines how to control coupled interdependent utility systems in defense operations.

“One of the ultimate goals for us is to move beyond the doctrine of ‘shock and awe’ and be more strategic about debilitating adversaries,” he said

The Department of Defense’s MURI program supports research by teams of investigators that intersect several traditional science and engineering disciplines to accelerate research progress. Rice is one of 43 academic institutions that are expected to participate in the 15 MURI programs awarded in 2013.

The list of projects selected for fiscal 2013 funding may be found at:
www.defense.gov/news/2013MURITeams.pdf