Shmuel Fishman
Shmuel Fishman, an accomplished physicist and a professor emeritus at the Technion – Israel Institute of Technology, died on 2 April 2019. He was 70 years old. Through his long career, Fishman worked on a series of topics within the field of physics and allied fields.
Fishman was born in Vilnius in 1948 and moved to Israel in 1958. His childhood was difficult. He suffered from polio and endured the premature death of his parents. Fishman was then raised by cousins. He developed his interest in physics as a teenager, and despite his difficult childhood, he was able to pursue his undergraduate studies at the Hebrew University in Jerusalem.
Fishman did his PhD at Tel Aviv University. At the time, a new theory, renormalization group, was revolutionizing the understanding of phase transitions. Fishman was fascinated by this new approach and chose to study under Amnon Aharony, an expert in that field. In his PhD, Fishman made important contributions to our understanding of phase transitions in random magnetic systems. The notion of randomness was a recurring theme in Fishman’s research throughout his long and fruitful career.
After his PhD, Fishman worked with Michael Fisher at Cornell University and then the University of Maryland. While at Maryland, Fishman attended a seminar about an open problem, a fundamental difference between the dynamical behaviors of quantum and classical kicked rotators. Whereas the momentum of the classical kicked rotator seemed to diffuse, its quantum counterpart would eventually localize. Fishman, together with his colleagues D. R. Grempel and R. Prange, showed that this mysterious phenomenon is just a dynamical version of Anderson localization, in which interference between random trajectories leads to localization of wavefunctions. This seminal paper solved an important open question by connecting seemingly different fields.
In 1983 Fishman moved to the faculty of physics at the Technion in Haifa, Israel. Work on the kicked rotator piqued his interest in the intricate connections between quantum and classical mechanics. This question was at the time at the heart of the emerging field called quantum chaos. During his first decade at the Technion, Fishman worked on a diverse set of topics, such as dynamical localization, the dynamics of systems driven by high-frequency fields, and how classical periodic orbits are manifested in quantum properties, such as the scarring of wavefunctions. Due to those contributions, Fishman is considered one of the pioneers of quantum chaos.
Fishman’s love of science was reflected in his diverse choice of research topics. He developed a theory that explained the resonances observed when free-falling atoms are periodically kicked. He also studied a phase transition observed in a chain of ions inside a harmonic trap. Perhaps the best example of Fishman’s endless curiosity was his collaboration with a cardiologist, Guy Dori, in which they applied chaos theory to the dynamics of mammal hearts.
Throughout this time, Fishman’s curiosity also extended to topics outside of his physics career. His friends and large extended family knew him as a keen analyst of international and local politics. His time spent abroad, both during his years in the US and subsequent stints in multiple countries, led to a keen interest in food and history as well. This curiosity extended to the careers, research, and interests of his relatives and close friends, distant as they often were from physics.
One of Fishman’s main research interests in the last decade was the study of transport in disordered systems. In these, Anderson localization is possibly broken due to a competing effect, such as interactions between the particles or external driving. These systems are relevant to experiments in nonlinear optics and cold atoms. With his student Yevgeny Bar Lev (Krivolapov), Fishman showed that Anderson localization is marginally stable in disordered nonlinear Schrödinger equations, with spreading of wavepackets, which is at most logarithmic. Some of this research was motivated by experiments on nonlinear disordered optical lattices, performed in the lab of Moti Segev at the Technion. In these experiments the random change of the refractive index in space mimics the fluctuation of an external potential in time. Such fluctuations can broaden the light beam faster than can normal diffraction. In collaborative work, Fishman, Bar Lev, and their colleagues from Segev’s group demonstrated this broadening experimentally and also developed a theory that explained this effect.
Fishman enjoyed the process of overcoming difficulties on his way to discover something new about our world. He had very little patience to colleagues who put their personal biases before the scientific merit of their work. Despite this non-nonsense approach, and perhaps due to it, Fishman was very highly regarded by his colleagues and relatives alike.
Fishman was a wonderful mentor and supervisor. He deeply cared for his graduate students and was always ready to offer help and guidance. At the same time, Fishman expected his students to do research according to his high standards. His influence can be seen by the large number of former graduate students who followed Fishman’s example and are pursuing a scientific career.
In his last years, Fishman spent a significant amount of time becoming closer with his family in Israel and the US. Though at times introverted by nature, relatives were impressed by Fishman’s intelligence and amused at his precision in all matters. Friends and family alike remember fondly not just Fishman’s scientific achievements but also his lively political discussions and his incredible generosity to all those around him.
Fishman is buried in Haifa, Israel, near the Technion. He is survived by a niece, a nephew, and several cousins.
