Scientists have for some time postulated that "dark matter" could partially account for evidence of missing mass in the universe, while the hypothetical form of energy known as "dark energy" is the most popular way to explain recent observations that the universe appears to be expanding at an accelerating rate and accounts for 74 percent of the total mass-energy of the universe according to the standard model of cosmology. To better understand these two mysterious cosmic constituents scientists at the Los Alamos National Laboratory (LANL) are using Roadrunner, the world’s fastest supercomputer, to model one of the largest simulations of the distribution of matter in the universe.

Even though it’s looking at only a small segment of the “accessible” universe, the “Roadrunner Universe” model requires a petascale computer because, like the universe, it’s mind-bendingly large. The model’s basic unit is a particle with a mass of approximately one billion suns (in order to sample galaxies with masses of about a trillion suns), and it includes 64 billion and more of those particles.

According to Salman Habib, of the Laboratory’s Nuclear and Particle Physics, Astrophysics and Cosmology group the Roadrunner Universe model will help scientists really understand how to more completely and more accurately describe the observable universe, to assist in the design of future experiments and interpret observations from ongoing observations like the Sloan Digital Sky Survey-III.

“We are particularly interested in the Large Synoptic Survey Telescope (LSST) in Chile, in which LANL is an institutional member, and DOE and NASA’s Joint Dark Energy Mission (JDEM),” said Habib. “To do the science in any sort of reasonable amount of time requires a petascale machine at the least.”

The Roadrunner Universe model relies on a hierarchical grid/particle algorithm that best matches the physical aspects of the simulation to the hybrid architecture of Roadrunner. Habib and his team wrote an entirely new computer code that aggressively exploits Roadrunner's hybrid architecture and makes full use of the PowerXCell 8i computational accelerators. They also created a dedicated analysis and visualization software framework to handle the huge simulation database.

“Our effort is aimed at pushing the current state of the art by three orders of magnitude in terms of computational and scientific throughput,” said Habib. I’m confident the final database created by Roadrunner will be an essential component of dark universe science for years to come.”

As previously reported, the Roadrunner supercomputer was the first to break the petaflop barrier and it is being used for a number of projects aside from Habib’s team’s efforts to model the origins of the unseen universe.

Other projects selected to use Roadrunner include building the world’s largest HIV evolutionary tree that may lead researchers to new vaccine focus areas, simulating laser plasma interactions to understand inertial confinement fusion, and examining how nanowires break under stress to see how the movement of single atoms can change a material’s mechanical or electrical properties. Sounds like it has plenty to keep it busy.