Remembrance of Steve Pieper by Bob Wiringa
Steven C. Pieper (1943-2018) was a long-time member of the Physics Division at Argonne National Laboratory, having arrived in 1972 as a postdoctoral research associate, and staying on as an Assistant Physicist (1974), Physicist (1978), and Senior Physicist (1996) before "retiring" in 2011. He co-authored more than 100 papers and remained very active, with more than 20 of those papers coming after becoming a "self-endowed researcher." He was also one of the best-known computational physicists at Argonne, playing an important role in developing the Speakeasy computer language, the Ptolemy program for direct reaction calculations, and being a leading early user (and debugger) of many successive laboratory computers, especially the parallel machines starting with the IBM-SP1 up to the current front-line Mira and Theta machines. He was looking forward to working on the next-generation exascale Aurora.
Steve received his B.S. from the University of Rochester in 1965 and his Ph.D. from the University of Illinois at Urbana-Champaign in 1970, followed by a first postdoc at Case Western Reserve. At Argonne in the mid-1970s, he collaborated with Malcolm Macfarlane and Mark Rhoades-Brown to develop Ptolemy, initially for heavy-ion reactions, but later used also for light-ion rare-isotope reaction studies. Ptolemy is still actively used by many experimental groups and Steve maintained the source to keep it up-to-date with successive operating systems.
In the early 1980s he began a long-running collaboration with new Argonne postdoc Bob Wiringa and Prof. Vijay Pandharipande from the University of Illinois, using quantum Monte Carlo methods to study many-body problems ranging from atomic helium clusters to light nuclei and neutron drops. Along with later students from Illinois, including Joe Carlson and Rocco Schiavilla, this work attained significant recognition in the nuclear physics community, with results being featured in NSAC long-range plans. In 2000, Steve and Bob shared the University of Chicago Medal for Distinguished Performance at Argonne National Laboratory, along with Steve's long-time collaborator Rusty Lusk of the Mathematics and Computer Science Division.
Later, Steve and Bob shared the 2010 American Physical Society Tom W. Bonner Prize in Nuclear Physics - the highest award from the APS for nuclear physics. In 2017, DOE selected a 1997 paper by Illinois student Brian Pudliner, Pandharipande, Carlson, Pieper and Wiringa as one of the 40 Office of Science Research Milestones over the past 40 years.
Steve's activity continued well beyond his retirement, as he worked to improve and expand the QMC calculations, adapting them to ever-larger computer systems and nuclei, and training a new generation of researchers, including Saori Pastore, Alessandro Lovato, Diego Lonardoni, and Maria Piarulli. He also was continuously available to others in the division, particularly for computational questions and for research questions in general. His friendly expertise will be sorely missed.