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Focus on APS Topical Groups

Group on Few Body Systems

By Michael Lucibella

A notable moment for the APS Topical Group on Few Body Systems (GFB) came at the 1989 APS meeting in Baltimore, where the group sponsored a now famous symposium on cold fusion. The subject was all over the media after Martin Fleischmann and Stanley Pons controversially claimed to have produced fusion in their lab. At the high profile meeting, eight of the nine speakers refuted the Fleischmann-Pons claims, roundly rejecting the recent cold fusion assertions.

This year marks the 25th anniversary of GFB. The Group’s main purpose has always been to bring together a broad range of scientists who work on atomic and subatomic systems involving three or more particles. By taking this interdisciplinary approach to research, GFB may be the most scientifically diverse of all topical groups.
Few body systems can yield some of the most fiendishly complex problems to work with. Single and two body systems involve only a small number of variables while much larger systems can be simplified by studying their overall dynamics statistically. That middle range is where the number of variables quickly becomes overwhelming and has often stymied attempts to precisely model atomic and nuclear behavior. But results in this area have led to advances in fusion research and an overall better picture of the universe. Few body interactions between hydrogen and helium atoms play an important role throughout the observable cosmos.

Bringing together a wide variety of scientific disciplines to the group has allowed the sharing of techniques that work across many fields. Though the forces acting between different particles may differ, the tools and methods for calculating their properties are often the same. This allows disciplines ranging from atomic physics to physical chemistry to come together and share their knowledge.

The group can trace its origins back to several older organizations. Starting in 1965, the International Few Body Conferences, typically occurring every two years, served as the major gathering for physicists working on various few body problems and research. Nuclear physicists made up the audience of the first two meetings, before other fields began to filter in by 1974.

A few years later in 1977 theoretical chemist Don Kouri and nuclear theorist Yeong Kim submitted a proposal to the Gordon Research Foundation to create a parallel series of interdisciplinary conferences on few body physics. These conferences laid the groundwork for the later GFB by enthusiastically reaching out to different fields. One of the core principles of these Gordon Conferences was to keep the presentations on a reasonably technical level so that the chemists could fully understand the physicists’ presentations and vice-versa.

In 1982, however, the International Union of Pure and Applied Physics (IUPAP), acting under the recommendation of the APS Division of Nuclear Physics, refused to sponsor the tenth Conference on the Few Body Problem. The IUPAP said that there had been too many such conferences and demanded a three-year hiatus. To combat this unwelcome intrusion, participants at the 1984 Gordon Conference circulated a petition asking APS to dedicate one of its newly announced Topical Groups to Few Body Physics.

Frank Levin, Founding Chairman of the GFB, remembers the petition well, “The response of the attendees at the 1984 Gordon Conference was overwhelmingly positive–I think everyone signed the petition urging the formation of the GFB–and of course the rest is history.”

Since its inception twenty-five years ago, GFB has stayed true to its interdisciplinary approach to few body problems. Today the group is made up mostly of nuclear and atomic physicists, but also incorporates members in molecular physics, physical chemistry, particle physics, and even some specialists in condensed matter research.

“The group’s main focus was and I believe still is to be an umbrella organization that brings together researchers in different disciplines…who work on few-body problems and multiparticle dynamics,” Levin said.

While the group’s focus may not have changed over the years, the technology and methodology certainly has. An infusion of better computing power and more accurate measurements has brought a previously unheard of level of precision to the complex field.

“When we started, two and three body problems were the limit of what we could do,” said Wayne Polyzou of the University of Iowa, current Chair of the Group, adding that computers now can calculate the interactions of up to ten bodies, “This has transformed nuclear physics from twenty-five years ago from a qualitative type of science to something more quantitative.”

One of the major issues facing the Few Body Group has been low membership rates in recent years. The group grew initially from its start of around 100 members, but then began to plateau. Today, at 310 members, it is the smallest topical group, just passing the minimum of 300 required members. The Gordon Conferences have been discontinued because of low attendance.

“I am quite hopeful that we can bring it back up,” said Ravi Rau, Chair Elect, “We used to be a bit larger. We’ve always been small.”

The Group is always tirelessly recruiting. At the upcoming April Meeting, clipboards will be circulated at workshops that would be interesting to potential members of GFB. In addition, members of the group plan on vigorously appealing to students, since they are allowed to be members of up to two APS units free of charge.

Members of the group are always pushing the limits of precision. “When you deal with small systems, you can do complete calculations and measurements” Polyzou said, “You really can do realistic physics.” 

Gray arrow  Group on Few Body Systems Website

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Editor: Alan Chodos