Dennis Nemeschansky wears a blue, collared shirt and stands outdoors in front of leafy background.
USC Dornsife physics professor Dennis Nemeschansky changed prevailing thought on quantum field theory. (Photo: Peter Zhaoyu Zhou.)

Physicist deeply understood the beauty of his subject

An expert on string theory who broke the mold of quantum field theory, USC Dornsife physicist Dennis Nemeschansky was devoted to helping students share his appreciation for the beauty and elegance of his field.
Susan Bell

Dennis Nemeschansky, professor of physics and astronomy at USC Dornsife College of Letters, Arts and Sciences, died on June 1. He was 67.

An expert on string theory who focused on supersymmetry quantum field theory, Nemeschansky is best known for the Minahan-Nemeschansky Theory, which he developed with visiting physicist Joseph Minahan during a game of golf.

Published in 1997, their paper showed that the then-current approach to constructing certain types of important supersymmetric quantum field theories was incorrect and demonstrated the correct way to do it. Initial skepticism from the scientific community gradually gave way to respect and acceptance a decade later, as the theory continued to hold true under scrutiny.

An ink illustration depicts Dennis Nemeschansky sitting on a skateboard while holding a fire extinguisher and surrouned by thought bubbles containing math formulae.
This caricature of Dennis Nemeschansky demonstrating Newton’s Third Law using a skateboard and a fire extinguisher was drawn by his former student Kayan Sarpelleh in 2016. (Image: Courtesy of David Nemeschansky.)

Moreover, they were able to generalize their result to construct several more theories that completed a connection between these supersymmetric quantum field theories and a deep mathematical classification result.

Nemeschansky’s teaching focused on pre-med physics, and he taught “Physics for the Life Sciences” (PHYS 135) for more than 30 years.

Stephan Haas, chair of the Department of Physics and professor of physics and astronomy, said Nemeschansky would be sorely missed by faculty and students alike.

“Dennis had a great sense of humor, passion for science and ability to communicate complex material in a very understandable way,” Haas said.

Indeed, Nemeschansky wasn’t shy about using his considerable athleticism to illustrate the properties of physics to his students and could be spotted each semester demonstrating Newton’s Third Law by whizzing across campus on a skateboard with a fire extinguisher attached.

“Students and colleagues loved his casual and relatable attitude,” Haas said. “In his research, he made seminal contributions to our understanding of quantum field theory and string theory, their application to unification of forces, and on strong-weak coupling duality in supersymmetric quantum chromodynamics.”

A true calling

Nemeschansky was born in Helsinki, Finland, on Dec. 21, 1955. His father, Arje, was a salesman of kitchen equipment and his mother, Joan, worked in pharmaceutical sales. Nemeschansky was brought up in the Jewish faith, attending Hebrew school in Helsinki.

His son, alumnus David Nemeschansky ’15, who earned undergraduate degrees in political science from USC Dornsife and in communication from USC Annenberg School for Communication and Journalism as well as a progressive masters from USC Leventhal School of Accounting, said his father was one of the lucky few blessed with a true calling in life.

“He always knew from a very young age that math and physics were his thing,” he said. “It actually made his parents very nervous because he just wanted to do numbers and really had no patience or interest in any other subject.”

After completing his national service in the Finnish Army, Nemeschansky obtained an MSc in theoretical physics from Helsinki University of Technology in 1980. He then moved to the United States to earn his PhD at Princeton University in 1984, where he collaborated with and was taught by some of the leading physics minds of the day. It was also where he decided to study string theory, which he specialized in throughout his career.

After Princeton, he moved to Stanford University, where he completed his postdoctoral training at the Stanford Linear Accelerator Center in 1986.

The move to California proved decisive.

“Coming from Finland’s cold, dark winters, he fell in love with the sunny paradise of California and really wanted to stay here,” said David Nemeschansky.

The promising young physicist was invited to give a talk at USC’s inaugural string theory conference in 1985 and joined USC Dornsife the following year.

He had this personality where he wanted things done right — 98% wasn’t good enough.

He was recruited with Itzhak Bars, professor of physics and astronomy, to create a new theoretical physics group within the department.

“Most of these new hires were string theorists. My father was really excited about that and the possibility of working with those folks and building out something new at USC,” David Nemeschansky said.

A devoted teacher and mentor to his students, Nemeschansky took office hours very seriously, offering more than was required of him.

“He believed that you had to really understand physics and the mathematical backing behind it; you couldn’t just memorize formulas,” David Nemeschansky said. “He felt very strongly that people need to be taught in a way that shows them that beauty and elegance. And then they would never have to memorize a formula; they would see how it all ties together.”

While David Nemeschansky was a student at USC, he remembers his father inviting him to attend a lecture in which he would demonstrate how the entire physics textbook could be derived from two formulas. “I remember watching people in the first 15 minutes meticulously taking notes as he’s doing all these graphs on the chalkboard — he had no notes, it was all in his head. And then you could slowly see the atmosphere in the room turn to awe because it was very clear that his understanding was so deep.”

Disinterested in becoming department chair because he preferred to concentrate on his teaching and research, Nemeschansky did serve as colloquium chair, organizing physics symposiums and bringing in expert speakers to talk to faculty and doctoral students. He also served as scheduling chair, compiling the department’s class schedules.

In 1995 and 2004, he was a visiting fellow at the European Organization for Nuclear Research on the French-Swiss border, the location of the world’s most powerful particle accelerator. He also spent the summer of 2018 at TRIUMF in Canada.

Prior to his death, Nemeschansky wrote a physics textbook tailored to health students with USC Dornsife’s Scott Macdonald, assistant professor (teaching) of physics and astronomy. MacDonald is currently in talks with a publisher.

A passion for family, physics, sports — and books

David Nemeschansky remembers being impressed by his father’s extensive library.

“I used to joke that in his office he had a ‘wizard library.’ He really was trying to figure out the great mysteries of the universe, how matter is constructed, how the tiniest subatomic particles work. How many dimensions are there? How did the universe begin?”

In addition to his life-long passion for physics, Nemeschansky was a huge sports enthusiast.

“My father was a man of a very clear priorities: family, physics and sports — in that order,” said David Nemeschansky.

He was a keen ice hockey player and was so talented at tennis that at university he had to choose between a professional career in the sport and physics. His love of physics won.

Nemeschansky was also a talented soccer player and became an avid golfer in middle age.

“He had this personality where he wanted things done right — 98% wasn’t good enough,” David Nemeschansky said. “He had immensely high standards — for instance, he would rather not publish than publish something that was mediocre.” That exacting nature translated into sports.

“He really wanted me to have outstanding hockey training and he felt he was the only person who could do that, so he became my coach.”

The modest Finn

Nemeschansky may have been a perfectionist, but by all accounts, he was also an extremely modest, private man who asked students to call him by his first name.

Dennis Nemeschansky, wearing a black and yellow rain coat and a black hat operates a camera on a tripod to take a photograph of a waterful under a bridge.
Dennis Nemeschansky’s zeal for photographing waterfalls earned him the family nickname “Captain Tripod.” (Photo: Courtesy of David Nemeschansky.)

He is fondly remembered by faculty, staff and students as a brilliant but self-effacing man who inevitably had an undone shoelace.

“He was a man of few words. He didn’t really talk much about himself unless asked and even then, if you asked him where he went to school, he would say ‘back East.’ He wouldn’t say ‘Princeton,’” said David Nemeschansky.

Nemeschansky spoke fluent Finnish, Swedish and English and some Hebrew.

A believer in Judaism who saw ample room for God and physics to go hand in hand, Nemeschansky regularly attended synagogue.

In 1988, he married Lauren Rosen, a grade schoolteacher who later became a successful realtor.

Nemeschansky loved to travel and enjoyed photographing waterfalls so much his family nicknamed him “Captain Tripod.”

He retained great affection for the country of his birth throughout his life despite feeling it was a little small.

“He had bigger dreams, and that eventually took him to the U.S.,” said David Nemeschansky. “He married an American, had American children, but he stayed a Finnish citizen until he died. He loved his country.”

Nemeschansky is survived by his mother; his wife; his sons, David and Marc; and his brothers, Ben and Michael.