Karl T. Hecht

Karl T. (Ted) Hecht, a University of Michigan theoretical physicist, passed away peacefully on 18 June 2017 in Chelsea, Michigan. Ted distinguished himself through insightful use of group theory in nuclear physics and his exemplary mentoring of students and research associates.

Born in Stuttgart, Germany, on 11 June 1926, Ted and his two sisters escaped Nazi Germany for England in 1939 through the Kindertransport rescue effort. His father, who was a medical doctor and Dachau survivor, reunited with his family in Dearborn, Michigan, in 1940. Ted entered the University of Michigan at age 16. His studies were interrupted in 1944 when he was called to serve in the US Army in Germany. He resumed his studies in 1946 and received his PhD in 1955, at which time he was invited to join the faculty, ascending to the rank of full professor in 1965. Ted retired in 1997.

Ted had a legendary teaching and mentoring career that culminated in lecture notes and books like his Quantum Mechanics, published by Springer, that are valued for their mathematical rigor, which he exploited in his research. Many Michigan students credit Hecht with giving them one of their most memorable educational experiences through the breadth and clarity of his lectures. Most significantly, Ted will always be remembered by his PhD students as an outstanding thesis adviser.

Ted’s research mentor was David Dennison, who was a major contributor to our understanding of spin, and a leader in the theory of infrared spectra. He suggested that Ted explore hindered internal rotations within molecules. Ted quickly developed an elegant description that was credited by Townes and Schawlow in the text Microwave Spectroscopy (McGraw Hill, 1955) well before he finished his analysis of the microwave spectrum of methyl alcohol that was the main theme of his PhD thesis.

In the early 1960s, sensing emerging opportunities to use group theoretical techniques in nuclear physics, Ted began efforts to provide a fully microscopic understanding of nuclear collective phenomena, extending the techniques of Racah and others to higher symmetries, like SU(N) for spatial and the Wigner supermultiplet theory for spin–isospin degrees-of-freedom. Starting with light nuclei, building on Elliott’s pioneering work on the SU(3) model, Ted, working in parallel with Arima and his group in Japan and that of Moshinsky in Mexico, very clearly demonstrated that special symmetries can be used to yield a very simple understanding of rotational spectra in nuclei.

Ted and a student provided tables of Wigner and Racah coefficients that spurred a Michigan–Tokyo team to develop SU(3) coupling and recoupling methodologies that were coded into a comprehensive SU(3) package. These tools were used to extend the theory to heavy nuclei through the pseudo-SU(3) model which builds upon the pseudo-spin concept that was independently developed by the Hecht and Arima teams. Additional extensions of these concepts were applied to the orthogonal and symplectic groups, compact and non-compact. The efforts by Ted and his group have even recently found application in the development of a SU(3) based no-core shell-model theory.

An important additional step in the use of group theoretical techniques in nuclear physics was achieved with vector coherent state theory (VCS) that can be used to identify physically relevant representations of Lie groups. The VCS concept is elegantly described in Ted’s book The Vector Coherent State Method and its Application to Problems of Higher Symmetries (Berlin Springer, 2013). Ted’s ideas have also found application in particle physics in deriving realistic N–N interactions from quantum chromodynamics.

Ted was a senior fellow of the Alexander von Humboldt Foundation and a fellow of the American Physical Society. He was honored in 1991 through a Symposium, “Group Theory and Special Symmetries in Nuclear Physics,” that brought together at the University of Michigan experts in the field. But above all, Ted will be remembered as a kind and generous person who enjoyed the profound respect of colleagues and students.

Ted will be sincerely missed by all whose lives he touched.