It’s a good thing John W. Clark’s father was mistaken many years ago about Flash Gordon’s occupation or else the younger Clark might not have the distinguished scientific career that he has today.
At the impressionable age of 3, John Clark was enthralled by Flash Gordon, the main character in a popular science-fiction comic strip that his father read him every Sunday morning. One day, John asked his father what Gordon did for a living; John’s father replied, “He’s an inventor, a scientist.” Right then and there young John decided: “That is what I want to be.”
Photo by David Kilper
John W. Clark, Ph.D., the Wayman Crow Professor of Physics and chair of physics in Arts & Sciences, works on a problem with Haochen Li, a doctoral student who has been his research assistant for four years and served as his teaching assistant in two courses. “John has been a great adviser and mentor to me,” says Li. “I especially respect him for his original mind, his energy and dedication to research. Almost every time I talk with him about research, I get inspired by him.”
“Flash Gordon was actually a football player, I later learned. So if my father had said that, I would have been in real trouble,” says Clark, Ph.D., the Wayman Crow Professor of Physics and chair of the Department of Physics in Arts & Sciences.
Clark’s career is distinguished by a wide-ranging involvement in both traditional and non-traditional branches of theoretical physics.
For more than three decades he has played a prominent role in finding methods to solve the Quantum Many-Body Problem: How can one predict, quantitatively, the measurable properties of a large system of strongly interacting quantum particles — such as neutrons, electrons or atoms — from a knowledge of the intrinsic properties of the particles and the basic interactions between them? How does one solve the formidable equations given by quantum theory to determine the nature of the rich, complex, entangled “whole,” from its vastly simpler “parts”?
The methods developed by Clark have yielded fundamental new insights into the nature of the matter inside nuclei and neutron stars, the exotic quantum phenomena of superfluidity and Bose-Einstein condensation in quantum fluids, and the properties of strongly correlated electronic systems and spin lattices.
“John has played a truly commanding role in the international community of quantum many-body theorists for at least the last 30 years,” says Raymond F. Bishop, Ph.D., professor of theoretical physics at The University of Manchester in England, who leads the largest many-body theory group in the United Kingdom.
“He is, simultaneously, both one of the most highly respected researchers in the field at the professional level and one of the best liked at the personal level. He has helped to shape the evolution of the field in many ways, ranging from actively supporting the careers of the best young researchers to forcefully highlighting for the community those places where advances were needed.
“His lucid exposition of ‘the crisis in nuclear matter theory’ around 1978 was a vivid example of the latter,” Bishop explains.
“Thus, at a time when many members of the many-body community considered the field to be ‘mature,’ John persuasively pointed out that, indeed, all was not well. The resolution of this ‘crisis,’ in which John himself played a leading role, brought huge advances of understanding to the field that still reverberate today.”
In recognition of his pioneer-ing work in many-body physics — which dates back nearly 50 years to his seminal doctoral thesis on the method of correlated basis functions — Clark received the premier prize in the field, the Eugene Feenberg Memorial Medal, in 1987.
The Clark family at John Clark’s installation as the Wayman Crow Professor. From left, first row: John; wife, Carolena van den Berk; daughters Sabrina Runge, Carissa Clark and Jessica Clark-Glass. Back row, sons Marcel van den Berk and Eugene Clark. Not pictured is daughter Mathilde Walter Clark, who lives in Denmark.
The medal, which has been awarded to two scientists who went on to win Nobel Prizes, was named in memory of Feenberg, who was Clark’s doctoral adviser, friend and colleague at Washington University.
The son of a banker and a master teacher, Clark grew up in Lockhart, Texas, a small town 30 miles south of Austin. He attended the University of Texas, earning both a bachelor’s degree (1955) and master’s degree (1957) in physics.
Clark was attracted to nuclear physics, which was the frontier in physics at the time, and decided on WUSTL for his doctoral studies because Feenberg, one of the stars of nuclear theory, was on the faculty. Clark was Feenberg’s first student to do research in many-body theory.
After earning a doctorate in 1959, Clark headed to Princeton University for a National Science Foundation fellowship working with Eugene Wigner, another “Eugene” who had a major influence on Clark. Wigner won the 1963 Nobel Prize in physics.
Clark joined the WUSTL faculty in 1963 as assistant professor of physics, was promoted to associate professor in 1966 and full professor in 1972, and served as interim chair in 1996-97. The father of six, Clark has been chair since 2002 and plans to step down in July.
He thought so highly of Feenberg — who was like a second father to him — as well as of Wigner, that he named his son Eugene after the two esteemed theoretical physicists.
Clark felt “on top of the world” when he was selected the second Feenberg Medalist, as well as in 1999 when he was named the Wayman Crow Professor, a title Feenberg also held.
His close, fruitful relationship with Feenberg and Wigner might explain why Clark has mentored more doctoral students in theoretical physics — including six while serving as chair — than anyone else in his department’s history.
And of the last six, he is proud of the fact that three have been women, reflecting his concern about the worldwide shortage of women physicists.
“For the first 25 students I mentored to the Ph.D., only one was a woman,” he says. “Then in a span of four or five months starting in December 2005, three women I had supervised finished their Ph.D.s.
“It’s a reflection of something I have strived to make happen,” adds Clark. “Out of 91 graduate students today, 27 percent are women. That is definitely high among physics departments. It’s clear that we have really passed the threshold — there are enough women now who can provide mutual support for further increases.”
John W. Clark
Honors: Awarded Alfred P. Sloan Foundation Fellowship in 1965; elected fellow of the American Physical Society in 1972; feted on his 60th, 65th and 70th birthdays at international scientific meetings.
In print: Published some 250 articles in professional journals and books; co-edited and co-authored nine books.
Interests: Spending time with his family, particularly his first grandchild, 6-month-old Andrew; owning high-performance cars; collecting and reading science fiction; levada hiking on Madeira.
Current car: Silver BMW M3 with “WUPHYS” license plates; cars he misses: 1960 Corvette, 1966 Lotus Elan and a 1967 Mini Cooper S.
And he’s also happy to report that on his watch the department recruited its first female faculty member on the tenure track, Yan Mei Wang, Ph.D.
Aikaterini Mandilara, Ph.D., a postdoctoral fellow at the Laboratoire Aime’ Cotton in Orsay, France, says she was fortunate to have had Clark as her thesis adviser.
“John Clark as an adviser has the significant ability to direct without suppressing the enthusiasm of personal discovery,” Mandilara says. “In spite of his long, successful career in physics, he didn’t try to impose his interests but he let me develop my own taste for physics and be able to think independently.”
“He is the hardest working professor I’ve ever known,” says Haochen Li, a doctoral student in physics who has been Clark’s research assistant for four years. “I often get research instructions in e-mails from him at midnight. And if you come to school on weekends, you will always find a fresh pot of coffee in the kitchen — which has been made by him.”
Clark also has the respect and admiration of faculty and staff who recognize that he’s been able to effectively manage the department while continuing a distinguished research program in a challenging field by working long and hard.
“John’s tenure as department chair has been marked by quiet diplomacy,” says James G. Miller, Ph.D., the Albert Gordon Hill Professor of Physics. “He is a strong and effective leader who has led a diverse and sometimes demanding faculty with graciousness and kindness.”
Since the mid-1970s, Clark’s research has been increasingly crossdisciplinary. An early interest in neural networks as models for brain function led to work with Charles H. Anderson, Ph.D., research professor of neurobiology, aimed at a theory of neural information processing that embodies fundamental principles of probabilistic inference expounded by Edwin T. Jaynes, Clark’s illustrious predecessor in the Wayman Crow chair.
Another line of research, conducted in the 1980s with T.J. Tarn, Ph.D., professor of systems science & mathematics, resulted in papers that provide the theoretical foundation for the burgeoning field of quantum control, which is at the heart of laser manipulation of chemical reactions and proposed designs for quantum computers.
Charles E. Campbell, Ph.D., a distinguished condensed matter theorist at the University of Minnesota, was a doctoral student at WUSTL when Clark was an associate professor. Campbell says Clark has had a major impact as a collaborator with and mentor to hundreds of physicists worldwide and is a leader in his roles on numerous international advisory committees and editorial boards and as organizer of many conferences in several different subfields of physics.
“His lectures at professional meetings have been invaluable,” says Campbell. “They are deep and thorough, both pedagogical and trailblazing. In the many-body physics community, I believe that he is more often asked to give plenary lectures at professional meetings than any other member of that community, which speaks to the importance and timeliness of his research as well as to his ability to communicate.
“And, as a former chair of my department, I can only be amazed at the continual level of his research accomplishment and leadership while he serves as chair.”
To Clark, it’s all about making a contribution and feeling the excitement of discovery. “As you answer one question, many more questions appear,” he says. “It’s a rich, complex universe. What we are doing is exploring it. And there’s no end to that.”