James Ricker Wilson

Computational physicist, astrophysicist, and general relativist James Ricker Wilson died on 14 August 2007 in Livermore, California, of a rare form of lymphoma.

Jim was born on 21 October 1922 in Berkeley, California. After earning a BS degree in chemistry in 1943 from the University of California, Berkeley, he immediately joined the Manhattan Project. There he did research on the properties of plutonium.

An anecdote about his first research problem highlights Jim’s ability to find simple solutions to complex problems, a trait that characterized his career. When he arrived at Los Alamos, his supervisor handed him a pea-sized chunk of dull grayish metal and said, “This is the world’s supply of plutonium. I’m going to lunch. Please brief me on its metallurgical properties when I get back.” Jim pondered his task, then put the pellet on an anvil and smacked it with a hammer. He later reported to his supervisor that it was malleable. As he recounted later, it fortunately was very impure plutonium; otherwise, it would have pulverized and contaminated the entire building.

Jim returned to UC Berkeley in 1946 and earned a doctorate in theoretical physics, for studies in the theory of mesons, in 1952. After a year at Sandia National Laboratories in Albuquerque, New Mexico, he returned to California to join the Lawrence Livermore National Laboratory, where he worked until his death. He was also an adjunct professor of physics at the University of Notre Dame from 1996 to 2007. His expertise in computational physics developed from his studies of nuclear explosions. His early work involved classified projects in the design and hydrodynamic simulation of nuclear explosions. Those projects laid the groundwork for a whole category of essential tools for understanding and designing nuclear weapons. In 1968, however, he spent a sabbatical year at Cambridge University to study astrophysics. For the next 37 years, he applied much of his computational expertise to public research.

In the early 1970s, he did foundational work in the fields of numerical relativity and numerical relativistic hydrodynamics. Besides his work on supernova collapse, which led to an understanding of delayed neutrino heating mechanisms for supernova explosions, and on the neutrino-energized bubble as a site for heavy-element nucleosynthesis, he was among the first to numerically compute collapsing stars, relativistic rotating stars, and magnetized stars; relativistic jets; accreting Kerr black holes; and colliding binary black holes and neutron stars.

Both Jim’s classified work and his work in astrophysics dealt with systems too complex to be fully described in any feasible computer program. Both areas of his work also involved some poorly understood facets of the underlying physics. As a result, getting meaningful answers required a person to have a barely definable quality that could be called “good taste in physics.” Such good taste combines a clear grasp of the basic processes involved and their likely interplay, a feeling for what quantities will mainly determine the process under investigation, and some intuition. Jim’s success in both fields was in good measure due to his good taste in physics, together with a willingness not to be daunted by the complexity of the problems.

Jim was recognized professionally with the Marcel Grossman Award in 1994 for his work in relativistic astrophysics and with the American Physical Society’s Hans A. Bethe Prize in 2007 for his nuclear astrophysics and numerical work on supernova core collapse, neutrino transport, and shock propagation. The APS recognition was particularly appropriate because Bethe was a regular visitor to Livermore and collaborated with Jim on core-collapse supernovae. The two often pored over the output of Jim’s codes into the night. On one occasion, Bethe returned early the next morning and announced—correctly—that there must be an error in the computer calculation, as it had not agreed with the computation he had done by hand overnight.

Mountaineering was Jim’s other great passion in life. He met his wife, Demetra Corombos, while climbing in the Canadian Bugaboos in 1947. Jim was known for his mountain adventures, including annual weeklong family backpacking trips in the High Sierras in California; those trips continued a tradition established by his father in 1903. Jim made rock-climbing first ascents in the Yosemite Valley and Sequoia National Park and mountaineered in British Columbia. In 1965, as part of a six-member team, he made a month-long ascent of Hummingbird Ridge on Canada’s Mount Logan, considered the hardest mountaineering route in North America; that’s a feat no one has repeated. He was also the first to ski California’s John Muir Trail without caches in April 1975.

Jim will be missed by all who knew him. His lively and creative mind, his uncanny physics intuition, his fierce determination, and his mischievous sense of humor were great gifts. He was a tireless collaborator, mentor, and motivator, as typified by his last phone conversation with one of us (Mathews), which ended with the same exhortation that he gave in every other conversation: “Now, get to work!”