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Section site map: News |
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NewsIn the beginningSDSC and NCSA help simulate the early universe in unprecedented detail. Download a pdf of the print version.
The filamentary structure in this simulation in a cube 1.5 billion light years on a side is also seen in real life observations such as the Sloan Digital Sky Survey. A particularly massive galaxy cluster, with a mass 2 quadrillion times that of the sun, can be seen near the center. Images courtesy of Matt Hall, NCSA. Unlike most scientists, astronomers have a way to do "time travel," literally seeing back into the universe's early history. A number of "red shift" surveys are taking this trip, recording objects in one section of the sky that are ever farther away-and therefore older--as their light travels billions of years to reach the earth. To help understand these observations, UC San Diego cosmologist Michael Norman and collaborators are using the ENZO cosmology code to simulate the universe from first principles, starting near the Big Bang. In work submitted to the Astrophysical Journal, the researchers have conducted the most detailed simulations ever of a region of the universe 500 megaparsecs across (more than 1.5 billion light years). The size and detail of their results will be useful to other researchers involved in spatial mapping and simulated sky surveys, shedding light on the underlying physical processes at work. But to keep the model faithful to reality, the researchers need to represent the extreme variability of matter as it coalesces under gravity, becoming many orders of magnitude more dense in local areas. "We need to zoom in on these dense regions to capture the key physical processes--including gravitation, flows of normal and 'dark' matter, and shock heating and radiative cooling of the gas," says Norman. "This requires ENZO's 'adaptive mesh refinement' capability." Adaptive mesh refinement (AMR) codes begin with a coarse grid spacing and then spawn more detailed (and more computationally demanding) subgrids as needed to track key processes in higher density regions.
Michael Norman, UC San Diego. "We achieved unprecedented detail by reaching seven levels of subgrids throughout the survey volume--something never done before--producing more than 400,000 subgrids, which we could only do thanks to the two large-memory TeraGrid systems," says SDSC computational scientist Robert Harkness, who carried out the runs with astrophysicist Brian O'Shea of Los Alamos National Laboratory. Running the code for a total of about 500,000 processor hours, the researchers used 1.5 terabytes of shared memory on the SGI Altix system at NCSA, and 2 terabytes of memory on the IBM DataStar at SDSC. To achieve these computations, an ASTA collaboration between Harkness and Norman's group made major improvements in scaling and efficiency of the code. Using Amore, an NCSA-developed visualization tool that renders challenging AMR particle and volume data, visualization programmer Matthew Hall created high-quality visualizations. The simulations also generated some 8 terabytes of data. The Hierarchical Data Format Group, which recently spun-off from NCSA, provided important support for handling the output, and SDSC's robust data storage environment allowed the researchers to efficiently store and manage the massive data. More information |
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The TeraGrid project is funded by the National Science Foundation and includes 11 partners: Please email help@teragrid.org with questions or comments or out the convenient online feedback form. This site is XHTML 1.0 Transitional, CSS, & Section 508 compliant. |
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