University of California: In Memoriam, 1988
Hans Lewy, Mathematics: Berkeley
| 1904-1988 | |
| Professor Emeritus |
Hans Lewy, Professor Emeritus of Mathematics at the University of California at Berkeley, died on August 23, 1988, after a brief illness. He was 83. He is survived by his wife Helen, and a son, Michael.
Lewy was born on October 20, 1904 in Breslau, Germany. He had a brilliant academic career and was awarded a Ph.D. degree from the University of Göttingen a few months before his twenty-second birthday. He served as Privatdozent at the University for the next six years. In 1933 he left Germany for the United States and was a Research Associate at Brown University for two years. He came to the University of California, Berkeley, as a lecturer in 1935; thereafter he advanced through the ranks, becoming a full professor in 1946. He was noted in Berkeley for being a warm person with a fine sense of humor. He retired in 1972 but continued his scientific work with undiminished vitality.
Lewy's achievements were recognized throughout the world. He held Rockefeller Foundation Fellowships at the University of Rome (1929-30) and at the University of Paris (1930-1931). During the Second World War he had an appointment at the Aberdeen Proving Ground. He accepted appointments at Harvard and at Stanford between 1952 and 1954 and at New York University in 1959-60. He was accorded the honor of Professor Linceo at the Accademia Nazionale dei Lincei in Rome in the academic year 1969-70. He lectured on his work throughout the world, with visits to the Soviet Union, the People's Republic of China, India, Japan, Czechoslovakia, and virtually all the countries of western Europe.
Professor Lewy was a member of the National Academy of Sciences, the American Academy of Arts and Sciences, and the Academia Nazionale dei Lincei (Rome). He was awarded the Steele Prize of the American Mathematical Society in 1979, and shared the Wolf Foundation with K. Kodaira in 1986. In 1986 he was awarded an honorary doctorate by the University of Bonn.
Professor Lewy was known as a person of integrity and strong moral principles. In 1950, he refused to sign a special loyalty oath imposed on
Hans Lewy was one of the great mathematicians of the twentieth century; he showed unparalleled originality in his work, which was characterized by the unexpected. In 1957 he started the mathematical world by exhibiting a simple partial differential equation which has no solution at all, thus changing the thinking of the experts in the field.
In another of his best known works, written in 1928 with Courant and Friedrichs, he developed criteria for determining conditions which guarantee the stability of numerical solutions of certain classes of differential equations. This work turned out to be crucial later for the use of high speed computers in solving such equations; thousands of research articles have been written on numerical solutions of differential equations based on his pioneering work.
While still in Göttingen, he published a series of fundamental papers on partial differential equations and the calculus of variations. He solved completely the initial value problem for general nonlinear hyperbolic equations in two independent variables. On the basis of this, and using the daring idea of converting an elliptic equation into a hyperbolic one by penetrating into the complex domain, he developed a new proof of the analyticity of solutions of analytic elliptic equations in two independent variables, one which far exceeded the known proof in its elegance and simplicity. He proved the well-posedness of the initial value problem for wave equations in what is now called Sobolev spaces two decades before these spaces became a common tool for specialists. The revolutionary character of these works is reflected in the fact that J. Hadamard, a world authority at that time, devoted a special appendix to Lewy's theory in his newly published book on the Cauchy Problem (1932).
In his early Berkeley period, Lewy made important contributions to geometry by solving two outstanding problems, those of Minkowski and Weyl. The former is to construct a convex surface in three dimensional space that realizes a given curvature as a function of the direction of the normal. The latter is (in modern terminology) to imbed a compact, orientable, two-dimensional Riemannian manifold with positive Gaussian curvature isometrically into three-dimensional space. Lewy was able to solve these problems for analytic data, using his technique of extension into the complex domain and sharp a priori estimates he had deduced for the Monge-Ampere equation. Moreover he established decisive results in the theory of minimal surfaces, solving several outstanding problems such as the extendibility of a minimal surface across a part of its boundary as well as the analytic nature of the boundary which is free or partially free (such as flexible
The aforementioned discovery of an equation with no solution gave rise to two other profound papers which not only broke new ground in the theory of functions of several complex variables but also had a permanent influence on microlocal analysis. Lewy received the Steele prize for these works.
In recent years Lewy enjoyed working on the so-called obstacle problem, a kind of variational problem with one-sided constraints. It is yet another form of the free boundary problem of which he was so fond.
There are few publications by Lewy other than original research papers. One such is an introduction he wrote for the Dover edition of Riemann's collected works. Its closing paragraph may well be adapted to Lewy himself:
...we revere in this man, who was endowed with superb craftsmanship, the ethics of his endeavor which kept him remote from the blandishments of brilliance and forced him to search for deeper truths, hidden beneath the reflection of the surface of facts.
Courtesy of University Archives, The Bancroft Library, University of California at Berkeley, Berkeley, CA 94720-6000; http://bancroft.berkeley.edu/info
http://content.cdlib.org/view?docId=hb967nb5k3&brand=calisphere
Title: 1988, University of California: In Memoriam
By: University of California (System) Academic Senate, Author
Date: 1988
Contributing Institution: University Archives, The Bancroft Library, University of California at Berkeley, Berkeley, CA 94720-6000; http://bancroft.berkeley.edu/info
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