Nuclear Physics with Lattice QCD

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Jul. 11, 2006 | Science and Tech
Supercomputers help physicists understand a force of nature
CONTACT:  Vince Stricherz    206-543-2580    

What if the tiniest components of matter were somehow different from the way they exist now, perhaps only slightly different or maybe a lot? What if they had been different from the moment the universe began in the big bang? Would matter as we know it be the same? Would humans even exist?
Scientists are starting to find answers to some profound questions such as these, thanks to a breakthrough in the calculations needed to understand the strong nuclear force that comes from the motion of nature's basic building blocks, subatomic particles called quarks and gluons. The strong nuclear force that binds these particles together, which is also called quantum chromodynamics, is one of the four basic forces of nature, along with gravity, electromagnetism and the weak force. The strong nuclear force is very powerful at short ranges, binding quarks and gluons into neutrons and protons at the core of atoms.The basic equations that describe the nuclear force have been known since the mid 1970s, and were the subject of the 2004 Nobel Prize in physics. But physicists still know very little of how the force described by these equations binds protons and neutrons into the nuclei of atoms.Now a team of researchers using a supercomputer and a method called lattice quantum chromodynamics have been able to calculate interactions among neutrons and protons from the properties of quarks and gluons. The lattice essentially divides the space-time continuum into a four-dimensional grid, allowing the researchers to examine the effects of the strong force, which becomes important at distances of one 100-trillionth (or 10 -15) of a meter or less. The new calculation is a first step toward understanding how nuclear forces emerge from the interactions between quarks and gluons, said Martin Savage, a University of Washington physics professor who is part of the research team.  "We're showing that techniques exist today to compute a nuclear reaction from the underlying theory of strong interactions," Savage said. "It is a simple reaction in terms of neutrons and protons, but it is a start."  In fact, it is enough for theoretical physicists to begin tackling questions such as how the universe might be different if quarks were slightly lighter or heavier than they actually are. The work also will let researchers perform calculations that could, for instance, provide clearer understanding of what the interior of a body such as a neutron star looks like.  "This will help us to understand how finely tuned the universe is," Savage said. "If you change the values of the fundamental constants of nature, would the universe still produce stars? Or humans?"

The work is described in a paper published July 7 in Physical Review Letters. Other authors are Silas Beane, an assistant professor of physics at the University of New Hampshire; Paulo Bedaque, an assistant professor of physics at the University of Maryland; and Konstantinos Orginos, an assistant professor of physics at the College of William and Mary in Virginia and a member of the theory group at the Thomas Jefferson National Accelerator Facility in Virginia. Beane also is affiliated with the Jefferson facility. The work was paid for in part by grants from the U.S. Department of Energy and the National Science Foundation.
Having a framework to calculate nuclear interactions in terms of quarks and gluons paves the way for reaching a greater understanding of the nature of the universe, particularly as supercomputers become increasingly powerful in the coming years, Savage said.
"We can start to explore how the structure of nuclei would change if the quark masses differed from the values found in nature," he said. "We hope we can determine if the quark masses in nature, or values very close to them, are required for carbon-based life to exist in our universe, or if any old quark masses would do."


For more information, contact Savage at (206) 543-7481 or; Beane at (603) 862-2720 or; Bedaque at (301) 405-6115 or; or Orginos at (757) 221-3524 or 

UW professors awarded time with supercomputers

By Nathan Lee
January 17, 2007

At the recent Council on Competitiveness held in Washington D.C., the U.S. Department of Energy's Office of Science announced the names of 45 research projects that would share 95 million hours of supercomputing time in 2007.

Supercomputer facts

The Department of Energy (DOE) has one of the top 10 most powerful supercomputers in the world, and four of the top 100. A project that receives one million hours can run on 2,000 processors for 500 hours. A one million hour project on a single-processor would take over 114 years. Previous research applications were designing quieter cars, improving commercial aircraft design, advancing fusion energy, studying supernova, understanding nanomaterials, studying global climate change and studying the causes of Parkinson's disease. Made possible through the Innovative and Novel Computational Impact on Theory and Experiment (INCITE) program, among the 45 projects chosen were three involving UW professors. Created in 2003 by Raymond Orbach, director of the office of science, the purpose of INCITE is to seek out "computationally intensive, large-scale research projects with the potential to significantly advance key areas in science and engineering," according to the DOE Web site. While intended to primarily donate supercomputing time to select projects, INCITE also provides recipients with assistance from scientists and staff at the facilities across the U.S. that house the supercomputers. UW biochemistry professor David Baker, a 2007 INCITE recipient, said that supercomputers are simply very large computers with a large number of processors that can carry out large calculations. "There are two ways to create a supercomputer: by putting together a large number of processors or by linking personal computers together," he said. Granted three million processing hours at the Argonne National Lab in Illinois, Baker's research focuses on computing the structure of proteins with less than 150 amino acids with atomic-level resolution. "My group is working on developing a vaccine for HIV," he said. "Another project is to create an enzyme that stops the gene that causes malaria." For UW students interested in contributing to his work, Baker said they can donate processor time by going to and download the Rosetta program. A separate project granted three million hours at the Oak Ridge National Laboratory in Tennessee involves oceanography professor LuAnne Thompson. Working under a project title of Eulerian and Lagrangian Studies of Turbulent Transport in the Global Ocean, this research will complete the "first-ever centennial-scale eddy-resolving global ocean simulation," according to the INCITE proposal Web site. Also awarded time at the Oak Ridge National Laboratory, UW physics professor Martin Savage is a part of another research team awarded 10 million hours of supercomputing time. Savage said for his project, the supercomputers will be used to further understand the relations between the building blocks of matter such as quarks and gluons. "This will help us to understand how finely tuned the universe is," he said. "If you change the fundamental constants of nature, would the universe still produce stars? Or humans?"

Reach reporter Nathan Lee at