Nobel Prize in Physics- George Sudarshan & R.E Marshak ignored
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E. C. GEORGE SUDARSHAN
Professor, B.Sc. (Hons.), Madras (India), 1951; M.A., 1952; Ph.D., University of Rochester, 1958; D. Sc., Honoris. Causa, Wisconsin, 1969. Numerous honorary degrees. Padma Bhushan (Order of the Lotus) decoration by President of India, 1976. First Prize in Physics, Third World Academy of Sciences, 1985. Elementary particle physics, quantum optics, quantum field theory, gauge field theories, fibre bundles, classical mechanics, foundations of physics.
Date and Place of Birth. 16-9-1931, Kottayam, Kerala State, India. Nationality : American.
Office: RLM 9.328 // Office Phone: 471-5229
Email: sudarshan@physics.utexas.edu
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Doubt and Certainty.... coauthored with the eminent physicist, E.C.G. (George) Sudarshan. Sudarshan is Professor of Physics at the University of Texas, Austin. He was the author of the first theory of the weak nuclear force (the "V-A" theory), a pioneer in quantum optics, and the inventor of tachyons, hypothetical particles that travel faster than light. An expert on Indian philosophy, he is also the recipient of the Order of the Lotus, one of India's highest civilian honors, and has been nominated several times for the Nobel Prize. I first met Sudashan when I took his graduate course in quantum mechanics at UT, and we have been engaged in a continuous dialogue ever since....
wwwrel.ph.utexas.edu
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Advances in fundamental particle physics
Source: THE HINDU
November 18, 1999
THE SCIENCE and Technology section of The Hindu on October 14, contained a well written account of the work carried out by Professors G'.t Hooft and M. Veltman, for which they were awarded the prestigious Nobel Prize in Physics for this year. It is the purpose here to supplement the above write up by adding some more relevant and important developments in that field.
Professors Gerardus't Hooft and Martinus J.G. Veltman were awarded Nobel Prize for their work on the quantum structure of electroweak interactions. According to the Royal Swedish Academy of Sciences, "Their work has given researchers a well- functioning theoretical machinery which can be used for, among other things, predicting the properties of new particles". While M.J.G. Veltman (of the Netherlands) is retired from the University of Michigan, G.'t Hooft has been a professor at the University of Utrecht since 1977. He visited The Institute of Mathematical Sciences (MATSCIENCE), Chennai, in December 1994 and gave a seminar on his research work, 'Quantum Black Holes'.
In Nature, there are four basic forces: gravitational (which keeps the planets in cosmic order round the Sun, which returns the stone thrown vertically up, which causes tides in oceans etc.), electromagnetic (which keeps the electrons going round the nucleus of atoms, causes chemical binding etc), weak (responsible for the spontaneous beta-decay of heavy nuclei) and strong (which keeps the neutrons and protons inside the nucleus and keeps the quarks bound inside neutrons and protons). While the precise nature of the gravitational and electromagnetic interactions were well understood in the mid 1950's, that of the weak interaction was not at all clear.
E.Fermi applied a simple minded quantum field theory to explain the beta decay, incorporating the massless, chargeless but spin one-half particle, neutrino (suggested by W.Pauli) assuming only the vectorial type interaction. A major turning point came in December 1956 with the discovery of parity violation, predicted by T. D. Lee and C. N. Yang and experimentally confirmed by Madame C. S. Wu in the beta decay of Cobalt-60 nucleus.
Nevertheless the precise form of the weak force was not clear. A fundamental contribution by Professors E.C.George Sudarshan and R. E. Marshak in 1957 cleared the scenario by the conclusion that the only possible Universal Fermi Interaction (as weak interaction was called then) for weak processes was vector minus axial vector combination. This formed the basis of the weak force. The same conclusion was reached by Professors M.Gell-Mann and R. P. Feynman, a year after. It is very disappointing to write that these original proponents of the correct theory of weak interaction, E.C.George Sudarshan and R. E. Marshak, are not awarded the Nobel Prize for physics till date. It is fitting to quote (Late) R. P. Feynman, "We have a conventional theory of weak interaction invented by Marshak and Sudarshan, published by Feynman and Gell-Mann ans completed by Cabibbo - I call it the conventional theory of weak interactions - the one which is described as the V-A theory".
The ambition of unifying the basic forces of Nature to a single one is the dream of every particle physicist. A unification of electromagnetism (parity conserving long range force mediated by massles spin-1 particle) and weak force (parity violating short range force and so mediated by massive spin-1 particle) was achieved in the late 1960's by Professors A. Salam and S. Weinberg. Electromagnetism is described by Abelian gauge theory based on U(1) group and weak interaction by non- Abelian gauge theory based on SU(2) group. The non-Abelian generalization was first made in 1954 by C. N. Yang and R. L. Mills and independently by R. Shaw.
The 'conventional V-A' structure of weak interaction is very important here to choose the 'left SU(2)' which then allows one to write the weak current in a form similar to electromagnetic current. Both will be vector currents involving left and left- right spinor fields. This was made possible by introducing scalar fields at the beginning which by a symmetry breaking mechanism called Higgs mechanism, would generate masses for the carriers of weak interaction alone. In such a theory, there was a major problem of renormalisability. This is a special desired property of a quantum field theory which guarantees that the higher order corrections will not become disastrous and allows one to confidently carry out them to predict observable.
This technical issue involves divergent integrals (infinities) to be subtracted, computation of higher order corrections such that local gauge invariance is maintained. When Professors A. Salam and S. Weinberg proposed the electroweak unification involving leptons and later by Professors S. L. Glashow, J. Iliopoulos and L. Maiani including the quarks, they had no proof for the renormalisability of their theory but they strongly believed its renormalisability.
Professor M. Veltman was studying these issues in a non-Abelian gauge theory with explicit mass term, as in a model of S. L. Glashow (1961), for the gauge fields. The local gauge invariance was then lost. (Nuclear Physics, volume B7, 1968, page 637; volume B21, 1970, page 288). What Professor G'.t Hooft realised in 1970, as a student of M.Veltman, was a model in which the mass term was generated by Higgs mechanism was better to study renormalisability than the model with explicit mass term. G.'t Hooft first attacked massless non-Abelian gauge theories (the quantisation of non-Abelian gauge theories is more difficult and subtler than Abelian theories), including the gauge fixing and ghost terms (Nuclear Physics, Volume B33, 1971, page 173) and then proceeded to add the mass term through Higgs mechanism, establishing unitarity perturbatively (Nuclear Physics, Volume, B35, 1971, page 167).
In the words of G.'t Hooft, "finally, with M.Veltman, a correct procedure was launched, now called 'dimensional regularisation and renormalisation"' (Nuclear Physics, Volume, B44, 1972, page 189) and Volume B50, 1972, page 318). Herein, the theory was taken to (4 - e) dimension. Although non-integral dimensions are meaningless, in perturbative expansion, the Feynman amplitudes can be defined, the logarithmic divergences disappear and linear and quadratic divergences can be subtracted unambiguously.
Higher order corrections could be computed in weak interaction theory for the first time and definite predictions were made. This summarises the major work of G'. t Hooft and M.Veltman in the context of establishing the unified electroweak theory on a firmer mathematical footing. An essential ingredient of this remarkable scheme is the Higgs neutral scalar particle. The set of scalars introduced at the beginning, served to break the gauge symmetry spontaneously, give mass for the specific gauge fields, and after all these, one component survived. This surviving component, called Higgs scalar, is being looked for in the high energy physics laboratories. An experimental observation of this particle will put the electroweak theory on a higher pedestal.
The strong force is shifted from neutron-proton-pion sector to quark-gluon sector. Here the force is described by non-Abelian gauge theory based on unbroken gauge group SU(3). One feature of this theory, which is due to the gauge symmetry remaining unbroken, is that the forces become negligibly small at short distances and incredibly large at large distances of separation between quarks. The first feature goes under the name, 'Asymptotic Freedom'. It is remarkable that G.t Hooft in 1972 proved this feature but did not publish it. Around the same time, H. D. Politzur and independently D.Gross and F.Wilczek, proved this and published. This feature is strongly confirmed by experiments and the particle physicists expect a similar award for this feature in the near future.
(R. Parthasarathy- The Institute of Mathematical Sciences Taramani, Chennai, Tamil Naud,India) |
