Shvinger (Schwinger), Julius S.( The American physicist, Nobel Prize in Physics, 1965)
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Biography Shvinger (Schwinger), Julius S.
February 12, 1918, Mr.. - August 16, 1994
American physicist Julius Seymour Schwinger was born in New York and was the second son of Benjamin Schwinger and Bell (nee Rosenfeld) Julian Schwinger. Schwinger's father was a fashion designer and clothing. Precocious boy fascinated by reading scientific journals, technical articles in encyclopedias and books on physics in the next to the house of the public library branches. At the age of 14 he graduated from high school and entered the City College in New York, where he began work on separate articles on quantum mechanics. One of them, published in the journal 'Fizikal Review' ( 'Physical Review'), draws attention IA. Rabi. Rabi seeks to Z. Special scholarships at Columbia University, and in 1936. SH. Columbia University, graduated with a Bachelor. He continued his education at the University of Wisconsin-Madison and Purdue University as a scholar, and in 1939. returned to Columbia University to defend his doctoral dissertation.
After receiving his doctorate W. during the year remained at Columbia University as a Fellow of the National Research Council, and the next year holds as an assistant researcher at the University of California at Berkeley. In 1941, Mr.. it goes into Purdue University researcher, first, and then Associate Professor. In 1943, Mr.. he takes part in creating the atomic bomb in the Metallurgical Laboratory, University of Chicago, . operate under the auspices of the Manhattan Project, . and then in the same year transferred to the Massachusetts Institute of Technology, . which is included in the study on improvement of radar systems,
. full (real) professor of physics at Harvard University. Since 1973, Mr.. SH. - Professor of Physics, University of California at Los Angeles.
Outstanding achievements in theoretical physics, for which he was awarded the Nobel Prize, laid back when he showed interest in the fundamental nature of matter. As a result of research he was able to eventually combine the two most important theories of physics of XX century.: Quantum mechanics and special theory of relativity. Quantum mechanics originates from the radical ideas of Max Planck put forward by them in 1900, according to which the energy of radiation consists of discrete portions (quanta). Quantum mechanics was formulated in the early 20-ies. in an attempt to explain the structure of the atom. In 1905, Mr.. special theory of relativity, Albert Einstein proved, inter alia, the equivalence of mass and energy - their mutual transformability.
In 1927, Mr.. P.A.M. Dirac used quantum mechanics and special relativity, . to record the relationship between electrons (a form of matter) and electromagnetic radiation (a form of energy, . includes light) in his theory of quantum electrodynamics,
. According to the Dirac theory, the quantum of electromagnetic energy (called photons), with sufficient energy can be 'materialized' in an electron and a previously unknown particle - positron. The latter is an analogue of the electron in the anti-matter (with the same mass but with opposite electric charge and other properties). Similarly, the collision of an electron and a positron, they annihilate, and their mass comes from the photon energy. Dirac's work has allowed a fuller understanding of the interaction between electrically charged particles and between particles and fields. For example, two neighboring electrons interact by exchanging a series of photons. Reaction force, . acting on each electron (return), . when it emits a photon, . and tells him the momentum in the absorption of a photon explain the electromagnetic repulsion between the particles, . carrying the same type of electric charge, . which tends to breed them with each other,
. Since the exchange photons of very short-lived and can not be detected directly, they are called virtual particles.
According to the uncertainty principle, formulated in 1927. Werner Heisenberg, the maximum energy of a particle is inversely proportional to the time allotted by nature for its measurement. Virtual photons are just a short time, that their energy can be very large. Furthermore, when the interaction of electrons closer together, the lifetime of virtual photons is even shorter, and the limit of possible values of energy rises more. When a single electron emits and then absorbs the virtual photon, the photon lifetime tends to zero, therefore, allowable values of energy and the equivalent weight tend to infinity.
By that time, when W. began its work, physicists realized the absurdity of one local in the Dirac theory. This theory predicts that each electron possesses an infinite mass and infinite electric charge. And since it was known that the electron mass and charge not only finite but very small, the falsity of this prediction was evident. Although the infinity, or divergence, were unclear, for many purposes they can be ignored (and indeed neglected), and Dirac's theory accurately predicted the outcome of many experiments.
In 1947, Mr.. Willis S. Lamb and Robert Rutherford experimentally found that the energy level of a single electron in a hydrogen atom slightly shifted relative to the value predicted by Dirac. About the same time Polycarp Kusch and several of his colleagues at Columbia University found that the magnetic moment of the electron is slightly different from the predicted value.
To resolve these discrepancies, W. and Itiro Tomonaga, working independently from each other, were subjected to quantum electrodynamics critical review.
Instead of deliberately ignoring the infinite values of the mass and charge of the electron W. Tomonaga and take advantage of these divergences. In their view, the measured electron mass must consist of two components: the true electron mass and the mass associated with a cloud of virtual photons (and other virtual particles) that constantly emits an electron and then absorbs. An infinite mass of the cloud of photons and the infinite, but the negative electron mass almost cancel each other out, leaving a small ending balance, which corresponds to the measured mass. To solve the mystery of the infinite electron charge, W. Tomonaga and postulated the existence of infinitely large negative bare charge, attracting positively charged cloud of virtual particles that shield almost the entire negative charge. Experimentally observed value corresponds to the final balance of uncompensated negative bare charge.
Proposed W. Tomonaga and procedure (mathematical method, called renormalization) provides a sound conceptual basis of quantum electrodynamics. Excluding one infinity, it introduces others, such as infinite negative mass. But since the electron can not be separated from the cloud of virtual particles, infinite mass and infinite bare charge of the electron never observed. Therefore, as stressed by W. and Tomonaga, the only measurable quantities during the renormalization of the masses are finite positive. Renormalization ceased to be controversial or questionable theory: it has been tested experimentally, and its predictions were in agreement with measurements.
Working around the same time, regardless of W. and Tomonaga, Richard F. Feynman chose a completely different but equally fundamental approach to the construction of quantum electrodynamics. He saw the ends of the trajectory along which a particle followed, and the relative probabilities of possible interactions that a particle could undergo a 'road'. The summation of the different probabilities allows to describe these interactions. Although arising in such a summation series sometimes have an extremely complex structure, . Feynman proposed quantum electrodynamic rules, . allowing to provide interaction in the form of simple and elegant graphical charts, . currently known under the name of Feynman diagrams,
. They were powerful and convenient means of solving problems in quantum electrodynamics.
In 1965, Mr.. S., Feynman and Tomonaga were awarded the Nobel Prize in Physics for "fundamental work in quantum electrodynamics, had profound implications for the physics of elementary particles'. In his Nobel lecture W. addressed the issue of extending its operations to other areas of physics: 'The experiment reveals a growing number and variety of unstable particles ... Of course, we hope that all this amazing complexity - no more than a dynamic manifestation of a conceptually simple substrate ... Notion of a relativistic field is a concrete implementation of this general tendency to search for new concepts of matter '.
In addition to work on quantum electrodynamics, W. made an important contribution to the development of nuclear physics and electrodynamics (the theory of waveguides). For example, in 1957,. He conjectured, . according to which neutrinos (massless particle, . predicted by Enrico Fermi, . who proposed and its name) must exist in two forms: one, . associated with the electron (electron neutrino), . another, . associated with the heavier particles, . called a muon (muon neutrino),
. Both neutrinos were first detected in the 60-ies. In subsequent years, W. accomplished many works in theoretical elementary particle physics, follows its own unique approach.
In 1947, Mr.. SH. married Clarice Carrol. Children spouses Schwinger was not.
In addition to the Nobel Prize, W. was awarded the University medal of Columbia University (1951), Prize Albert Einstein Memorial Foundation Lewis and Rosa Strauss (1951) and the National Medal 'For his scientific achievements' of the National Science Foundation (1964). He is an honorary doctorate from Purdue, Harvard, Brandeis and Columbia. SH. is a member of the U.S. National Academy of Sciences, the American Physical Society, the New York Academy of Sciences, as well as the American Association of Basic Sciences and the American Academy of Arts and Sciences.