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Physics Professor, Alumni Publish 'Jamming Dynamics' in Scholarly Journal

David Egolf

David Egolf

April 1, 2013 – A Georgetown physics professor and three Georgetown alumni recently published a paper in Nature Physics that explores the behavior of granular materials.

David Egolf, associate professor of physics, Edward Banigan (C‘07), Matthew Illich (C‘11), and Derick Stace-Naughton (C‘11), published their report, “The Chaotic Dynamics of Jamming,” on March 24.

The co-authors examined how granular materials such as sand can exhibit behaviors not yet well understood in the physics community.

For example, sand can flow through a funnel without trouble but will eventually clog or “jam” as the rate of pouring increases.

Impact on Industries

“It has been estimated that a significant fraction of the U.S. gross domestic product is spent in the handling of granular materials,” the professor explains. “An understanding of their behavior, especially during storage and transport, would impact industries dealing with products ranging from grains and coal to fruits and pharmaceuticals.”

When forces are applied to jammed materials, they experience intermittent, dramatic events in which a collection of particles rearranges to relieve some stress on the system.

“This ‘stick-slip’-type behavior is closely related to the dynamics of tectonic plates in earthquakes,” Egolf explains.

Earthquake Physics

“Neither these rearrangement events nor the jamming transition are well understood, despite great effort in the community,” Egolf says. 

The co-authors used a new mathematical approach to find that unjammed states are chaotic, and jammed states are not chaotic. They also were able to predict the times and locations of the dramatic rearrangement events.

Because of the close connections between the physics of granular materials and the physics of earthquakes, Egolf says these advances may eventually lead to better predictions of earthquakes.

Keeping Students Involved

Both Banigan and Illich worked on the project as their senior theses. Stace-Naughton joined the project in the spring of 2011.  

“Our department has a strong history of getting students involved in research projects, no matter whether the students are planning to stay in science or not, and these three are a great example,” says Egolf.

Banigan is finishing his Ph.D. in physics at the University of Pennsylvania.

Illich is an analyst at The Amundsen Group, a pharmaceutical strategy consulting firm, and Stace-Naughton is pursuing an MBA at the Stanford Graduate School of Business. He completed a master’s degree in health communications last year as a Mitchell Scholar in Ireland.

Read the paper here.

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