OBITUARY: Professor Eugene Wigner

Eugene Paul Wigner, physicist: born Budapest 11 November 1902; Professor of Mathematical Physics, Princeton University 1938-71; Nobel Prize for Physics 1963; married three times (one son, two daughters); died Princeton, New Jersey 1 January 1995

History shows curious and unexplained concentrations of genius in certain places and at certain periods of time.

The conceptual revolution in physics that led to the recognition that the laws of nature on the microscopic level are fundamentally different from those of everyday objects was initiated by Max Planck's discovery, in 1900, of the ``quantum of action''. The birth of the quantum was accidentally paralleled by the births of those great physicists who, in the mid-Twenties, completed the revolution by formulating Quantum Mechanics: Paul A.M. Dirac (1902), Werner Heisenberg (1901), Pascual Jordan (1902), Wolfgang Pauli (1900) and Eugene Wigner (1902).

The citation for Wigner's Nobel Prize in 1963 tersely honoured him for ``systematically improving and extending the methods of quantum mechanics and applying them widely''.

Eugene Wigner was born in Budapest, where his father operated a tannery, and he studied at the Lutheran gymnasium in that city. All his life he recalled the excellent training he had received there and kept a picture of his mathematics teacher, Laszlo R a cz, in his study. One of his schoolmates, John (Jancsi) von Neumann, though by a few years his junior, tutored him in higher mathematics - little Jancsi became one of the greatest mathematicians of the century. Other notable contemporaries of Wigner's in Budapest were the physicists Leo Szilard and Edward Teller, the physical chemist George de Hevesy, the inventor Dennis Gabor and the aerodynamicist Theodor von Karman.

For a short period, in 1919, Hungary became a Soviet Republic. The events of that period left a deep mark on Wigner's mind and he became, in the period of the Cold War, staunchly anti-Communist (he remained, however, equally staunchly, a Hungarian nationalist).

Perhaps motivated by his father's business, and certainly evaluating his chances for an academic career in Hungary as very slight, young Wigner decided to study chemical engineering. He went to Berlin, and received in 1925 an advanced degree in that field from the Institute of Technology in Berlin-Charlottenburg. He came under the influence of Michael Polanyi, an eminent physical chemist and a fellow Hungarian, and began participating in the famous weekly seminars attended by Einstein and a galaxy of eminent scientists.

By 1927, Wigner emerged as one of the most innovative theoretical physicists of his time. He applied an abstract branch of mathematics known as ``group theory'' to problems of atomic structure as described by the new Wave Mechanics discovered just a yearor two before. This approach enables one to extract the maximum of information about a system, say an atom, molecule or nucleus, with a minimum of knowledge of its dynamics, i.e. of the forces acting between its constituents. It focuses the attention onthe symmetries, rather than the details, of the system. Wigner's approach, summarised in 1931 in a masterful book, Group Theory and its Application to Atomic Spectra, has dominated many fields of physics since its publication. W i thout it, our present detailed understanding of the world of elementary particles could have hardly ever been reached. Wigner himself applied it, in the mid-Thirties, to the systematic of atomic nuclei. His nuclear ``supermultiplets'' found their reflect ion in the families of elementary particles such as we know them today.

In 1930 Wigner joined Princeton University, first on a temporary and soon on a permanent basis. He thus escaped the persecution that forced so many of his colleagues to flee continental Europe a few years later. In 1939, shortly after the news of the discovery of uranium fision in Germany had reached the United States, he, together with his compatriots Leo Szilard and Edward Teller, persuaded Albert Einstein to write to President Roosevelt to warn him of the danger that Nazi Germany might develop an atomic bomb. After a slow start, this ``Hungarian initiative'' led to the gigantic secret project that ultimately produced the bombs at Los Alamos.

In 1942, Wigner took a leave from Princeton and joined Enrico Fermi at the University of Chicago, to build the first nuclear reactor. The prime goal of this reactor was to explore the production of plutonium, a fissionable element that does not occur in nature. Its success led to the building of large-scale reactors at Hanford, in Washington state. Wigner was largely in charge of this step, and the abstract theoretical physicist returned himself into a skilled engineer.

One of the many contributions of Wigner to reactor technology is the anticipation of the ``Wigner effect", i.e. the warming-up of the graphite moderator, damaged by neutron bombardment in the reactor, through self-healing.

Wigner made decisive contributions to any area of physics in which he took interest. Today's scientific jargon includes Wigner coefficients, Weisskopf- Wigner formula, Breit-Wigner resonance, Wigner crystals, Wigner energy and Wigner rules. He was, as a thesis supervisor, a successful teacher. Among his students, one may mention John Bardeen, the only physicist to receive two Nobel Prizes.

It is impossible to summarise Wigner's personality, philosophy and political outlook in a few lines. He was slight of build, almost frail and spoke mostly very softly, but always with an unmistakable Hungarian accent. His obstinate politeness has given rise to many amusing anecdotes. His outward behaviour did not, however, fully succeed in hiding an iron will and a correct appreciation of his own remarkable talents. Politically, he became in the post-war years an extreme conservative, urging

the construction of bomb shelters to minimise the effects of nuclear war, while most other physicists tried to find ways to prevent a nuclear holocaust altogether.

After his retirement from Princeton in 1971, Wigner concentrated on exploring the philosophical consequences of Quantum Mechanics. He became increasingly disenchanted with the orthodox, so-called Copenhagen interpretation of this subject, but did not formulate a viable alternative.