ACADEMIA

The Department of Energy (DOE) has awarded valuable computing time on one of the world's most powerful supercomputers to two research projects led by scientists at the University of California, Santa Cruz. The awards from DOE's 2007 Innovative and Novel Computational Impact on Theory and Experiment (INCITE) program will support research on supernovae (the explosions of massive stars) and the formation and evolution of the dark matter halo that envelopes the Milky Way galaxy. Piero Madau, professor of astronomy and astrophysics at UCSC, leads the dark matter project. Stan Woosley, also a professor of astronomy and astrophysics, is principal investigator on the supernova research project. Madau's group recently completed the largest simulation of the Milky Way's dark matter halo to date, using NASA's Columbia supercomputer. The INCITE award will allow the researchers to run an even larger simulation revealing much more detail of the galaxy-forming region of the halo, Madau said. "The simulation will start at about 50 million years after the Big Bang and calculate the interactions of 1 billion particles of dark matter over 13.7 billion years of cosmological time to produce a halo on the same scale as the Milky Way's. It seeks to increase our understanding of the nature of the dark matter that accounts for more than 80 percent of the matter in the universe," he said. Madau's coinvestigators on the project are Jürg Diemand and Marcel Zemp, both postdoctoral fellows at UCSC, and Michael Kuhlen at the Institute for Advanced Study in Princeton, New Jersey. The INCITE award gives Madau's group 1.5 million processor hours on the Cray XT3 supercomputer at the Oak Ridge National Laboratory, which is ranked as the tenth fastest computer in the world. Processor hours refer to how time is allocated on a supercomputer. A project receiving 1 million hours could run on 2,000 processors for 500 hours, or about 21 days. Running a one-million-hour project on a single-processor desktop computer would take more than 114 years. Woosley's group received 4 million processor hours on the Oak Ridge Cray XT3. The researchers will use the supercomputer to study key stages in the explosion of type Ia supernovae. Type Ia supernovae are the thermonuclear explosions of white dwarf stars, triggered when the star siphons off enough mass from a companion star to reach a critical mass of about 1.4 times the mass of the Sun. These supernovae are used for cosmic distance measurements because their brightness evolves over time in a predictable manner. "By acting as standard candles, type Ia supernovae have been at the forefront of a revolution in modern cosmology, leading to the discovery that the expansion of the universe is accelerating. We anticipate that the supercomputer calculations will produce the most detailed picture of type Ia supernovae to date," Woosley said. His coinvestigators include Ann Almgren, John Bell, and Marc Day of Lawrence Berkeley National Laboratory; L. Jonathan Dursi of the University of Toronto; Dan Kasen of Johns Hopkins University; Fritz Röpke of UC Santa Cruz; and Michael Zingale of the State University of New York, Stony Brook. Supercomputers are playing an increasingly important role in scientific research by allowing scientists to create more accurate models of complex processes, simulate problems once thought to be impossible, and analyze the increasing amount of data generated by experiments. Launched in 2003, the INCITE awards support computationally intensive, large-scale research projects and award them large amounts of dedicated time on DOE supercomputers. The 45 projects supported by the program in 2007 include applications ranging from studying global climate change to improving commercial aircraft design. They were chosen in a competitive process based on the potential impact of the science and engineering research and the suitability of the project for use of supercomputers.