Stanisław Ulam

From Wikipedia, the free encyclopedia

Stanisław Marcin Ulam (April 13, 1909 – May 13, 1984) was a Polish mathematician who participated in the Manhattan Project and proposed the Teller–Ulam design of thermonuclear weapons. He also invented nuclear pulse propulsion and developed a number of mathematical tools in number theory, set theory, ergodic theory, and algebraic topology.

Contents 1 Biography 2 Books 3 See also 4 Bethe on Ulam 5 Further reading 6 External links

[edit] Biography

Stanisław Ulam was born in Lwów (German: Lemberg; Ukrainian: Lviv), Galicia, in Austria-Hungary, now in Ukraine. He was part of the city's Polish majority population. His mentor in mathematics was Stefan Banach, a great Polish mathematician and one of the moving spirits of the Lwów School of Mathematics and more broadly of the remarkable Interbellum Polish School of Mathematics.

Ulam went to the US in 1938 as a Harvard Junior Fellow. When his fellowship was not renewed, he served on the faculty at the University of Wisconsin-Madison, and supported his brother, Adam, who had fled from Poland on the eve of the Second World War. While there, in the midst of the war, his friend John von Neumann invited him to a secret project in New Mexico. Ulam researched the invitation by checking out a book on New Mexico from the university library. There he found a list, on the library check-out card, of all those who had successively disappeared from the campus at the UW. Ulam then joined the Manhattan Project at Los Alamos.

While there, he suggested the Monte Carlo method for evaluating complicated mathematical integrals that arise in the theory of nuclear chain reactions (not knowing that Fermi and others had used a similar method earlier). This suggestion led to the more systematic development of Monte Carlo by Von Neumann, Metropolis, and others.

Ulam — in collaboration with C.J. Everett, who did the detailed calculations — showed Edward Teller's early model of the hydrogen bomb to be inadequate. Ulam then went on to suggest a better method. He was the first to realize that one could place all the H-bomb's components inside one casing, put a fission bomb at one end and thermonuclear material at the other, and use mechanical shock from the fission bomb to compress and detonate fusion fuel. This idea was probably an outcome of Ulam's initial ideas for 'staging' a conventional fission device, in which the neutron flux from one fission bomb would compress the fuel in another one, thus increasing its efficiency.

Teller at first resisted this idea, then saw its merit and suggested the use of a plutonium "spark plug", located at the center of the fusion fuel, to initiate and enhance the fusion reaction. Teller also modified Ulam's idea of compression by realising that radiation from the fission bomb would compress the thermonuclear fuel much more efficiently than mechanical shock. This design, generally referred to as staged radiation implosion, has been the standard method of creating H-bombs ever since. Although this approach was worked out independently by Soviet physicist Andrei Sakharov, it is often referred to as the "Teller–Ulam design". Ulam and Teller jointly applied for a patent on the hydrogen bomb.

Ulam also invented nuclear pulse propulsion and, at the end of his life, declared it the invention of which he was proudest.

He was an early proponent of using computers to perform "mathematical experiments." His most notable contribution here may have been his part in the Fermi–Pasta–Ulam experiments, an early numerical study of a dynamic system.

In pure mathematics, he worked in set theory (including measurable cardinals and abstract measures), topology, ergodic theory, and other fields. After World War II he largely turned from rigorous pure mathematics to speculative and imaginative work, posing problems and making conjectures (which had always been specialties of his) that often concerned the application of mathematics to physics and biology. His friend Gian-Carlo Rota ascribed this change to an attack of encephalitis in 1946 that Rota claimed changed Ulam's personality (though detail had never been Ulam's strong point). This suggestion is believed by many but rejected by Ulam's widow, Françoise, among others.

In May 1958, while referring to a conversation with von Neumann, Ulam said what would later became a foundation of the technological singularity theory: "One conversation centered on the ever accelerating progress of technology and changes in the mode of human life, which gives the appearance of approaching some essential singularity in the history of the race beyond which human affairs, as we know them, could not continue."

Ulam took a position at the University of Colorado in 1965. As he remained a consultant at Los Alamos, he divided his time between Boulder, Colorado, USA and Santa Fe, New Mexico, from which he commuted to Los Alamos. Later he and his wife spent winters in Gainesville, Florida, where he had a position with the University of Florida. He died in Santa Fe on May 13, 1984.

[edit] Books

• Stanisław Ulam, The Scottish Book: a Collection of Problems, Los Alamos, 1957.
• Stanisław Ulam, A Collection of Mathematical Problems, New York, Interscience Publishers, 1960.
• Mark Kac and Stanisław Ulam, Mathematics and Logic: Retrospect and Prospects, New York, Praeger, 1968. Dover paperback reprint edition ca. 1990.
• Stanisław Ulam, Sets, Numbers and Universes, Cambridge, Massachusetts, 1974.
• Stanisław Ulam, Adventures of a Mathematician, New York, Charles Scribner's Sons, 1983 (autobiography).

[edit] See also

• Borsuk-Ulam theorem
• Lucky number (1955)
• Ulam spiral (1963)
• Ulam conjecture
• Scottish Café
• Adam Ulam (Adam Bruno Ulam), Stanislaw's brother, a noted Kremlinologist at Harvard University.

[edit] Bethe on Ulam

• "After the H-bomb was made, reporters started to call Teller the father of the H-bomb. For the sake of history, I think it is more precise to say that Ulam is the father, because he provided the seed, and Teller is the mother, because he remained with the child. As for me, I guess I am the midwife." (Hans Bethe, 1968, as quoted by Schweber, p.166.)

[edit] Further reading

• Necia Grant Cooper, Roger Eckhardt, Nancy Shera, editors, From Cardinals to Chaos, Cambridge University Press (1989). Reminiscences by people close to Ulam, memorial articles on aspects of his work, and previously unpublished informal work by him.

[edit] External links

• O'Connor, John J., and Edmund F. Robertson. "Stanisław Ulam". MacTutor History of Mathematics archive.
• Annotated bibliography for Stanislaw Ulam from the Alsos Digital Library
• A biographical article on Ulam by Gian-Carlo Rota
• Stanisław Ulam at the Mathematics Genealogy Project
• [1] Ulam Quarterly Journal.
• Stan Ulam's Biography – from LANL