Sidney Dancoff
{{Short description|American theoretical physicist}}
{{Infobox scientist
| name = Sidney Dancoff
| birth_date = {{birth date|1913|09|27}}
| birth_place = Philadelphia
| death_date = {{death date and age|1951|08|15|1913|09|27}}
| death_place = Urbana, Illinois
| workplaces =
| alma_mater = University of California at Berkeley
| thesis_title = Three problems in quantum mechanics
| thesis_url = http://oskicat.berkeley.edu/record=b15408866~S1
| thesis_year = 1939
| known_for = Tamm–Dancoff approximation
| doctoral_advisor = Robert Oppenheimer
| doctoral_students = Sidney Drell
| spouse = Martha Friedman
| children = 2
}}
Sidney Michael Dancoff (September 27, 1913 in Philadelphia – August 15, 1951 in Urbana, Illinois) was an American theoretical physicist best known for the Tamm–Dancoff approximation method and for nearly developing a renormalization method for solving quantum electrodynamics (QED).
Early life
Dancoff was raised in the Squirrel Hill neighborhood of Pittsburgh. He attended Carnegie Tech on a private scholarship and received his B.S. in physics in 1934, followed by a master's degree from the University of Pittsburgh in 1936. He then went to the University of California at Berkeley where he earned his PhD in 1939 under Robert Oppenheimer.{{cite news |last=Lowry |first=Patricia |date=2011-04-10 |title=He wrote the law on risk-taking, yet theoretical physicist Sidney Dancoff couldn't save his own life |url=http://old.post-gazette.com/pg/11100/1137883-51.stm |archive-url=https://web.archive.org/web/20190418102221/https://old.post-gazette.com/pg/11100/1137883-51.stm |archive-date=April 18, 2019 |accessdate=2012-03-23 |newspaper=Pittsburgh Post-Gazette |location=Pittsburgh, PA}}
Career
While Dancoff was at Berkeley, Oppenheimer suggested that he work on the calculation of the scattering of a relativistic electron by an electric field. Such QED calculations typically gave infinite answers. Following earlier perturbation-theory work by Oppenheimer and Felix Bloch, he found that he could deal in various ways with the infinities that arose, sometimes by canceling a positive infinity with a negative one. However, some infinities remained uncanceled and the method (later called renormalization) did not give finite results. He published a general description of this work in 1939.S. M. Dancoff, Physical Review 55, p. 959 (1939){{cite book | author = S. S. Schweber | title = QED and the Men Who Made it: Dyson, Feynman, Schwinger, and Tomonaga | year = 1994 | location = Princeton | publisher = Princeton University Press | isbn = 0-691-03685-3 | url = https://archive.org/details/qedmenwhomadeitd0000schw | url-access = registration | accessdate = 2007-02-23}}
In 1948, Sin-Itiro Tomonaga and his students revisited this paper. Using improved calculational methods, they found that Dancoff had omitted one term{{cite web | author = S.-I. Tomonaga | title = Nobel Lecture | year = 1966 | publisher = Nobel Foundation | url = http://nobelprize.org/nobel_prizes/physics/laureates/1965/tomonaga-lecture.html | accessdate = 2007-02-23}} or two terms. Once they repaired this omission, Dancoff's method worked, and they built on it to produce a theory of QED, for which Tomonaga shared the Nobel Prize in 1965. (At the same time, American physicists discovered Dancoff's error and solved QED, relying less directly on Dancoff.)
During the Second World War, Dancoff worked on the theory of the newly invented nuclear reactors. To take into account how fuel rods could "shadow" other rods by absorbing neutrons headed toward the other rods, he and M. Ginsburg developed the Dancoff factor, still used in reactor calculations.S. M. Dancoff and M. Ginsburg, "Surface Resonance Absorption in {{sic|hide=y|Closely|-}}Packed Lattice", USAEC-report CP-2157 (1944).
After the war, Dancoff was on the faculty of the University of Illinois at Urbana-Champaign. In 1950 he published an approximation method for many-body theory that has been used in nuclear and solid-state physics.S. M. Dancoff, Physical Review 78, 382 (1950). Igor Tamm had found it in 1945,I. Tamm, Journal of Physics (USSR) 9, 449 (1945) and the method is now named after both.
In the late 1940s, Dancoff began a collaboration with the Viennese-refugee physician and radiologist Henry Quastler in the new field of cybernetics and information theory. Their work led to the publication of what is now commonly called Dancoff's Law. A non-mathematical statement of this law is, "the greatest growth occurs when the greatest number of mistakes are made consistent with survival".{{cite book | author = S. M. Dancoff and H. Quastler | year = 1953 | title = Essays on the Use of Information Theory in Biology | chapter = The Information Content and Error Rate of Living Things | editor = Henry Quastler| location = Urbana | publisher = University of Illinois Press}}
Death
Dancoff died of lymphoma in 1951 at the age of 37, after which his wife and two daughters moved to Los Angeles. In 1994, Dancoff's remains were reinterred at Mount Sinai Memorial Park Cemetery.
References
External links
= Archival collections =
- [https://libserv.aip.org/ipac20/ipac.jsp?session=168N1274B1357.418&limitbox_1=LO01+%3D+icos&menu=search&aspect=power&npp=10&ipp=20&spp=20&profile=rev-icos&ri=1&source=%7E%21horizon&index=.GW&term=SIDNEY+M.+DANCOFF+PAPERS%2C+1949-1951&x=9&y=12&aspect=power Sidney Michael Dancoff papers, 1949-1951, Niels Bohr Library & Archives]
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Category:University of Pittsburgh alumni
Category:Carnegie Mellon University alumni
Category:20th-century American physicists
Category:American nuclear physicists
Category:American theoretical physicists
Category:Scientists from Philadelphia