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| {{Infobox scientist
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| | name =Julian Schwinger
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| | image = Schwinger.jpg
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| | image_size = 180
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| | caption =
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| |birth_name=Julian Seymour Schwinger
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| | birth_date = {{birth date|1918|2|12|mf=y}}
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| | birth_place = [[New York City, New York]], [[United States|USA]]
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| | death_date = {{death date and age|1994|7|16|1918|2|12}}
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| | death_place = [[Los Angeles, California]], [[United States|USA]]
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| | nationality = [[United States]]
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| | field = [[Physics]]
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| | work_institution = [[University of California, Berkeley]]<br>[[Purdue University]]<br>[[Massachusetts Institute of Technology]]<br>[[Harvard University]]<br>[[University of California, Los Angeles]]
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| | alma_mater = [[City College of New York]]<br>[[Columbia University]]
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| | doctoral_advisor = [[Isidor Isaac Rabi]]
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| | doctoral_students = [[Roy Glauber]] <br>[[Ben R. Mottelson]] <br>[[Sheldon Lee Glashow]] <br> [[Walter Kohn]] <br>[[Bryce DeWitt]]<br>[[Daniel Kleitman]]<br>[[Sam Edwards (physicist)|Sam Edwards]]<br>[[Gordon Baym]]<br>[[Stanley Deser]]<br>[[Lawrence Paul Horwitz]]
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| | known_for = [[Quantum electrodynamics]]<br>[[Schwinger function]]<br>[[Schwinger model]]<br>[[Schwinger-Dyson equation]]s<br>[[Schwinger's quantum action principle]]<br>[[Rarita-Schwinger action]]<br>[[Lippmann-Schwinger equation]]<br>[[Schwinger parametrization]]<br>[[Spin-statistics theorem]]<br />[[Schwinger limit]]
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| | prizes = {{nowrap|[[Nobel Prize in Physics]] (1965) }}
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| | religion =
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| | footnotes =
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| }}
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| [[File:Julian Schwinger, 1965.jpg|thumb|Julian Schwinger, winner of the 1965 [[Nobel Prize in Physics]]. Original caption: "His laboratory is his ballpoint pen." ]]
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| '''Julian Seymour Schwinger''' (February 12, 1918 – July 16, 1994) was a [[Nobel Prize]] winning [[United States|American]] [[theoretical physicist]]. He is best known for his work on the [[theory]] of [[quantum electrodynamics]] (QED), in particular for developing a relativistically invariant perturbation theory, and for renormalizing QED to one loop order. Schwinger was a professor in the physics department at [[UCLA]].
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| Schwinger is recognized as one of the greatest physicists of the twentieth century, responsible for much of modern quantum field theory, including a [[Schwinger's quantum action principle|variational approach]], and the equations of motion for quantum fields. He developed the first electroweak model, and the first example of confinement in 1+1 dimensions. He is responsible for the theory of multiple neutrinos, Schwinger terms, and the theory of the spin 3/2 field.
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| ==Biography==
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| Julian Seymour Schwinger was born in New York City, to [[Ashkenazi Jews|Jewish]] parents originally from Poland, Belle (née Rosenfeld) and Benjamin Schwinger, a garment manufacturer,<ref>{{cite book |title=Climbing the mountain: the scientific biography of Julian Schwinger |publisher=Oxford University Press |year=2000 |first=Jagdish |last=Mehra |pages=1–5 }}</ref><ref>http://www.bookrags.com/biography/julian-schwinger-wop/</ref> who had migrated to America. Both his father and his mother's parents were prosperous clothing manufacturers, although the family business declined after the [[Wall Street Crash of 1929]]. The family followed the [[Orthodox Jewish]] tradition. He attended [[Townsend Harris High School]] and then the [[City College of New York]] as an undergraduate before transferring to [[Columbia University]], where he received his B.A. in 1936 and his Ph.D. (overseen by [[Isidor Isaac Rabi]]) in 1939 at the age of 21. He worked at the [[University of California, Berkeley]] (under [[J. Robert Oppenheimer]]), and was later appointed to a position at [[Purdue University]].
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| ===Career===
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| After having worked with Oppenheimer, Schwinger's first regular academic appointment was at [[Purdue University]] in 1941. While on leave from Purdue, he worked at the [[Radiation Laboratory]] at [[Massachusetts Institute of Technology|MIT]] instead of at the [[Los Alamos National Laboratory]] during [[World War II]]. He provided theoretical support for the development of [[radar]]. After the war, Schwinger left Purdue for [[Harvard University]], where he taught from 1945 to 1974. <!-- He married in 1947. -->
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| Schwinger developed an affinity for [[Green's function]]s from his radar work, and he used these methods to formulate quantum field theory in terms of local Green's functions in a relativistically invariant way. This allowed him to calculate unambiguously the first corrections to the electron magnetic moment in [[quantum electrodynamics]]. Earlier non-covariant work had arrived at infinite answers, but the extra symmetry in his methods allowed Schwinger to isolate the correct finite corrections.
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| Schwinger developed [[renormalization]], formulating [[quantum electrodynamics]] unambiguously to one-loop order.
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| In the same era, he introduced non-perturbative methods into quantum field theory, by calculating the rate at which [[electron]]-[[positron]] pairs are created by [[quantum tunneling|tunneling]] in an electric field, a process now known as the "Schwinger effect". This effect could not be seen in any finite order in perturbation theory.
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| Schwinger's foundational work on quantum field theory constructed the modern framework of field correlation functions and their [[Schwinger-Dyson equation|equations of motion]]. His approach started with a [[Schwinger's quantum action principle|quantum action]] and allowed bosons and fermions to be treated equally for the first time, using a differential form of [[Grassman variable|Grassman integration]]. He gave elegant proofs for the [[spin-statistics theorem]] and the [[CPT theorem]], and noted that the field algebra led to anomalous [[Schwinger terms]] in various classical identities, because of short distance singularities. These were foundational results in field theory, instrumental for the proper understanding of [[anomaly (physics)|anomalies]].
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| In other notable early work, Rarita and Schwinger formulated the abstract [[Wolfgang Pauli|Pauli]] and [[Markus Fierz|Fierz]] theory of the spin 3/2 field in a concrete form, as a vector of Dirac spinors. In order for the spin-3/2 field to interact consistently, some form of supersymmetry is required, and Schwinger later regretted that he had not followed up on this work far enough to discover supersymmetry.
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| Schwinger discovered that [[neutrino]]s come in multiple varieties, one for the [[electron]] and one for the [[muon]]. Nowadays there are known to be three light neutrinos; the third is the partner of the [[tau lepton]].
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| In the 1960s, Schwinger formulated and analyzed what is now known as the [[Schwinger model]], quantum electrodynamics in one space and one time dimension, the first example of a [[Color confinement|confining theory]]. He was also the first to suggest an electroweak gauge theory, an SU(2) gauge group spontaneously broken to electromagnetic U(1) at long distances. This was extended by his student [[Sheldon Glashow]] into the accepted pattern of electroweak unification. He attempted to formulate a theory of quantum electrodynamics with point [[magnetic monopoles]], a program which met with limited success because monopoles are strongly interacting when the quantum of charge is small.
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| Having supervised more than seventy doctoral dissertations, Schwinger is known as one of the most prolific graduate advisors in physics. Four of his students won Nobel prizes: [[Roy Glauber]], [[Benjamin Roy Mottelson]], [[Sheldon Glashow]] and [[Walter Kohn]] (in chemistry).
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| Schwinger had a mixed relationship with his colleagues, largely because of his source theory. Schwinger considered source theory as a substitute for field theory, although it is only a different point of view, a version of [[effective field theory]]. It treats quantum fields as long-distance phenomena, and does not require a well defined continuum limit. Source theory was considered overly formal and lacking in distinctness from quantum field theory, and the criticisms by his Harvard colleagues led Schwinger to leave the faculty in 1972 for [[University of California, Los Angeles|UCLA]]. It is a story widely told that [[Steven Weinberg]], who inherited Schwinger's paneled office in Lyman Laboratory, there found a pair of old shoes, with the implied message, "think you can fill these?". At UCLA, and for the rest of his career, Schwinger continued to develop source theory reformulations of quantum field theoretic results.
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| After 1989 Schwinger took a keen interest in the non-mainstream research of [[cold fusion]]. He wrote eight theory papers about it. He resigned from the [[American Physical Society]] after their refusal to publish his papers.<ref>{{Citation| title=Climbing the Mountain: The Scientific Biography of Julian Schwinger|author=Jagdish Mehra, K. A. Milton, Julian Seymour Schwinger|edition=illustrated|editor=[[Oxford University Press]]|year=2000|isbn=0-19-850658-9|page=550|url=http://books.google.com/?id=9SmZSN8F164C&pg=PA550&vq=resigned+american+physical+society+cold+fusion&dq=Julian+Schwinger+cold+fusion|publisher=Oxford University Press|location=New York}}, Also {{harvnb|Close|1993|pp=197–198}}</ref> He felt that cold fusion research was being suppressed and academic freedom violated. He wrote: "The pressure for conformity is enormous. I have experienced it in editors’ rejection of submitted papers, based on venomous criticism of anonymous referees. The replacement of impartial reviewing by censorship will be the death of science."
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| In his last publications, Schwinger proposed a theory of [[sonoluminescence]] as a long distance quantum radiative phenomenon associated not with atoms, but with fast-moving surfaces in the collapsing bubble, where there are discontinuities in the dielectric constant. Standard explanations, now supported by experiments, focus on superheated gas atoms inside the bubble as the source of the light {{Citation needed|date=October 2008}}, but Schwinger's methods tie back to his old quantum electrodynamic papers.
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| Schwinger was jointly awarded the [[Nobel Prize in Physics]] in 1965 for his work on [[quantum electrodynamics]] (QED), along with [[Richard Feynman]] and [[Shinichiro Tomonaga]]. Schwinger's awards and honors were numerous even before his Nobel win. They include the first [[Albert Einstein Award]] (1951), the U.S. [[National Medal of Science]] (1964), honorary D.Sc. degrees from Purdue University (1961) and Harvard University (1962), and the Nature of Light Award of the U.S. [[United States National Academy of Sciences|National Academy of Sciences]] (1949).
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| ===Schwinger and Feynman===
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| As a famous physicist, Schwinger was often compared to another legendary physicist of his generation, [[Richard Feynman]]. Schwinger was more formally inclined and favored symbolic manipulations in [[quantum field theory]]. He worked with local field operators, and found relations between them, and he felt that physicists should understand the algebra of local fields, no matter how paradoxical it was. By contrast, Feynman was more intuitive, believing that the physics could be extracted entirely from the [[Feynman diagram]]s, which gave a particle picture. Schwinger commented on Feynman diagrams in the following way,
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| {{cquote| Like the silicon chips of more recent years, the Feynman diagram was bringing computation to the masses.<ref>J. Schwinger, "Quantum Electrodynamics-An Individual View," J. Physique 43, Colloque C-8, Supplement au no. 12, 409 (1982) and "Renormalization Theory of Quantum Electrodynamics: An Individual View," in '' The Birth of Particle Physics'', Cambridge University Press, 1983, p. 329</ref>}}
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| Schwinger disliked Feynman diagrams because he felt that they made the student focus on the particles and forget about local fields, which in his view inhibited understanding. He went so far as to ban them altogether from his class, although he understood them perfectly well and was observed to use them in private.
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| Despite sharing the Nobel Prize, Schwinger and Feynman had a different approach to quantum electrodynamics and to quantum field theory in general. Feynman used a regulator, while Schwinger was able to formally renormalize to one loop without an explicit regulator. Schwinger believed in the formalism of local fields, while Feynman had faith in the particle paths. They followed each other's work closely, and each respected the other. On Feynman's death, Schwinger described him as
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| {{cquote| An honest man, the outstanding intuitionist of our age, and a prime example of what may lie in store for anyone who dares to follow the beat of a different drum.<ref>http://amasci.com/feynman.html; "A Path to Quantum Electrodynamics," Physics Today, February 1989</ref> }}
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| ===Death===
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| [[File:Julian Schwinger headstone.JPG|thumb|The headstone of Julian Schwinger at Mt Auburn Cemetery in Cambridge, MA.]]
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| Schwinger died of pancreatic cancer. He is buried at [[Mount Auburn Cemetery]]; <math>\frac{\alpha}{2\pi}</math> is engraved above his name on his tombstone. These symbols refer to his calculation of the [[anomalous magnetic dipole moment|correction ("anomalous") to the magnetic moment of the electron]].
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| ==Publications==
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| *Feshbach, H., Schwinger, J. & J. A. Harr. [http://www.osti.gov/cgi-bin/rd_accomplishments/display_biblio.cgi?id=ACC0109&numPages=57&fp=N "Effect of Tensor Range in Nuclear Two-Body Problems"], Computation Laboratory of [[Harvard University]], [[United States Department of Energy]] (through predecessor agency the [[United States Atomic Energy Commission|Atomic Energy Commission]]), (November 1949).
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| *Schwinger, J. [http://www.osti.gov/cgi-bin/rd_accomplishments/display_biblio.cgi?id=ACC0111&numPages=92&fp=N "On Angular Momentum"], [[Harvard University]], Nuclear Development Associates, Inc., [[United States Department of Energy]] (through predecessor agency the [[United States Atomic Energy Commission|Atomic Energy Commission]]), (January 26, 1952).
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| *Schwinger, J. [http://www.osti.gov/cgi-bin/rd_accomplishments/display_biblio.cgi?id=ACC0110&numPages=51&fp=N "The Theory of Quantized Fields. II"], [[Harvard University]], [[United States Department of Energy]] (through predecessor agency the [[United States Atomic Energy Commission|Atomic Energy Commission]]), (1951).
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| *Schwinger, J. [http://www.osti.gov/cgi-bin/rd_accomplishments/display_biblio.cgi?id=ACC0112&numPages=35&fp=N "The Theory of Quantizied Fields. III"], [[Harvard University]], [[United States Department of Energy]] (through predecessor agency the [[United States Atomic Energy Commission|Atomic Energy Commission]]), (May 1953).
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| * ''Einstein's Legacy'' (1986) Scientific American Library
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| ==See also==
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| *[[Schwinger function]]
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| *[[Schwinger model]]
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| *[[Schwinger–Dyson equation]]s
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| *[[Schwinger's quantum action principle]]
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| *[[Rarita-Schwinger action]]
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| *[[Lippmann–Schwinger equation]]
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| *[[Schwinger parametrization]]
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| *[[MacMahon Master theorem]]
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| ==References==
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| {{Reflist}}
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| ==Further reading==
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| *Mehra, Jagdish, and Milton, Kimball A. (2000) ''Climbing the Mountain: the scientific biography of Julian Schwinger''. Oxford University Press.
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| *{{cite arxiv |last=Milton |first=Kimball |title=Julian Schwinger: Nuclear Physics, the Radiation Laboratory, Renormalized QED, Source Theory, and Beyond |date=2006-10-09 |eprint=physics/0610054}} Revised version published as (2007) "Julian Schwinger: From Nuclear Physics and Quantum Electrodynamics to Source Theory and Beyond," ''Physics in Perspective'' '''9''': 70-114.
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| *Schweber, Sylvan (1994) ''QED and the men who made it: Dyson, Feynman, Schwinger, and Tomonaga''. Princeton Univ. Press: chpt. 7. ISBN 978-0-691-03327-3.
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| *Ng, Y. Jack, ed. (1996) ''Julian Schwinger: The Physicist, the Teacher, and the Man''. Singapore: World Scientific. ISBN 981-02-2531-8.
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| *{{citation |title= A quantum legacy: seminal papers of Julian Schwinger |volume= 26 |series= World Scientific series in 20th century physics |author= Julian Seymour Schwinger |editor= Kimball A. Milton |publisher= World Scientific |year= 2000 |isbn= 978-981-02-4006-6 }}
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| ==External links==
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| {{Wikiquote}}
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| *[http://www.osti.gov/accomplishments/schwinger.html Photograph, Biography and Bibliographic Resources], from the [[Office of Scientific and Technical Information]], [[United States Department of Energy]]
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| *[http://www.nobel-winners.com/Physics/julian_seymour_schwinger.html Julian Schwinger]
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| *[http://www.nobel.se/physics/laureates/1965/schwinger-bio.html Nobel Museum Biography]
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| *[http://holiker.narod.ru/five/schwinger-press.html fundamental work in quantum electrodynamics, with deep-ploughing consequences for the physics of elementary particles]
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| * {{MacTutor|id=Schwinger}}
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| {{Nobel Prize in Physics Laureates 1951-1975}}
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| {{Authority control|VIAF=108599721|GND=119206250}}
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| {{Persondata<!-- Metadata: see [[Wikipedia:Persondata]] -->
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| |NAME= Schwinger, Julian
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| |ALTERNATIVE NAMES=
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| |SHORT DESCRIPTION= American physicist
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| |DATE OF BIRTH= February 12, 1918
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| |PLACE OF BIRTH= [[New York City]], [[United States|U.S.]]
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| |DATE OF DEATH=July 16, 1994
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| |PLACE OF DEATH= [[Los Angeles]], [[United States|U.S.]]
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| }}
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| {{DEFAULTSORT:Schwinger, Julian}}
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| [[Category:Theoretical physicists]]
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| [[Category:American people of Polish-Jewish descent]]
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| [[Category:American physicists]]
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| [[Category:Jewish American scientists]]
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| [[Category:American Nobel laureates]]
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| [[Category:Nobel laureates in Physics]]
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| [[Category:National Medal of Science laureates]]
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| [[Category:Columbia University alumni]]
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| [[Category:Harvard University faculty]]
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| [[Category:Purdue University faculty]]
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| [[Category:University of California, Los Angeles faculty]]
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| [[Category:1918 births]]
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| [[Category:1994 deaths]]
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| [[Category:Burials at Mount Auburn Cemetery]]
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| [[Category:Alexander von Humboldt Fellows]]
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| [[Category:Townsend Harris High School alumni]]
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