Benny Lautrup In Memoriam
With great sadness we have learned that Benny Lautrup passed away last Friday. Benny Lautrup was an important figure at the Niels Bohr Institute and he was one of the founders of the theoretical particle physics group at the institute in the 1970’s. Undergraduate and graduate studies at the institute were followed by post-doctoral appointments at Nordita, Brookhaven National Laboratory, CERN, and at Institut des Hautes Etudes Scientifiques in Paris. He was appointed Associate Professor at the Niels Bohr Institute in 1972 (later promoted to Professor) and except for a few sabbaticals at mainly CERN he remained at NBI until retirement in 2009.
Benny Lautrup was known for his spectacular brilliance already from his student days. In his thesis, written with essentially no guidance, he closed gaps in the conventional treatment of the quantization of electrodynamics and in so doing introduced what later became known as the Nakanishi-Lautrup field, an essential ingredient in the more modern approach of BRST quantization. During his first post-doctoral appointments Benny Lautrup made frontier contributions to the analytical calculations of high-order terms of the expansion of the anomalous magnetic moment of electrons and muons. Together with W. Bardeen and R. Gastmans he performed in 1972 one of the first one-loop calculations in what is now known as the electroweak part of the Standard Model of particle physics, thus explicitly demonstrating renormalizability of the theory at that order based on the brand-new dimensional regularization scheme. A highly influential single-author paper on the high-order behavior of the perturbation theory in quantum electrodynamics followed a few years later, and Benny Lautrup together with P. Cvitanovic and R.B. Pearson also derived the first general formulas for the counting of Feynman diagrams at arbitrarily high orders in perturbation theory. Typically, after Benny Lautrup had become known world-wide for his abilities in solving highly challenging perturbative problems in quantum field theory he switched to the then new topic of numerical lattice gauge theory around 1980. Together with M. Nauenberg he demonstrated the huge potential of Monte Carlo calculations in that field. After a series of such fundamental contributions to theoretical particle physics Benny Lautrup started working on very different topics such as the theory of neural networks and problems in mathematical physics. During this later stage of his scientific career he also wrote a highly regarded textbook on the Physics of Continuous Matter that is used at many institutions world-wide.
With superb writing skills it is not surprising that Benny Lautrup also excelled in popular science writing. As an intellectual he was interested in, and engaged in, numerous topics also outside the narrow boundaries of natural sciences, and he displayed great skills at communicating sharp observations. Throughout his career he contributed regularly to newspapers and magazines with the kind of science outreach that is characterized by both deep insight in the subject matter and sheer love of good writing.
Benny Lautrup had an endearing and colorful personality that was both brutally honest and highly sensitive. He could dazzle not only in science and he was socially active on many fronts (including a stint with a theater troupe in Geneva while he was a Fellow at CERN) and his wild exploits were famous. As in physics, Benny Lautrup quickly tired of new social directions after a while, seemingly getting bored once he had reached his immediate goals. If there was one thing he could not stand, it was posturing and pompousness without any real quality and insight. At the Niels Bohr Institute he connected fabulously and generously with younger generations of physicists while at the same time remaining a very serious and influential force in institute politics. Together with colleagues Holger Bech Nielsen, Poul Olesen, and Jens Lyng Petersen, he was responsible for the institute’s transition from theoretical nuclear physics to theoretical particle physics at just the right time. In so doing, they managed strikingly to put the group on the map in theoretical physics, thus moving away from the nuclear physics focus in the early 1970’s. Similarly, Benny Lautrup’s switch to the theory of neural networks helped the Niels Bohr Institute expand in the then burgeoning new field of chaos and complexity theory more than a decade later. After retirement in 2009 Benny Lautrup was a much appreciated senior member of Niels Bohr International Academy, always ready with insightful and brilliant contributions to any topic of discussion. He is sorely missed.
January 8, 2025
Poul Henrik Damgaard