John Clive Ward

John Clive Ward
Born 1 August 1924
London, England
Died 6 May 2000 (aged 75)
Victoria, British Columbia
Nationality Australian, British
Fields Particle Physics
Bell Laboratories
University of Maryland
University of Miami
Carnegie Institute of Technology
Johns Hopkins University
Victoria University of Wellington
Macquarie University
Alma mater University of Oxford
Doctoral advisor Maurice H. L. Pryce
Notable students F. J. Duarte
Known for Electroweak theory
Quantum electrodynamics
Quantum field theory
Renormalization theory
Ward–Takahashi identity
Notable awards Guthrie Medal (1981)
Dirac Medal (1981)
Heineman Prize (1982)
Hughes Medal (1983)

John Clive Ward (1 August 1924 – 6 May 2000) was a British-Australian physicist. He introduced the Ward–Takahashi identity, originally known as "Ward Identity" (or "Ward Identities").[1][2] This result, in quantum electrodynamics, was inspired by a conjecture of Dyson[3] and was disclosed in a one-half-page letter typical of Ward's succinct style. In their recent book entitled Quantum Electrodynamics, Greiner and Reinhardt state in their discussion of charge renormalisation: "Yet the Ward Identity has a much more fundamental significance: it ensures the universality of the electromagnetic interaction."[4]

In his book The Infinity Puzzle, Frank Close devotes a chapter to this Ward identity and entitles the chapter "The Identity of John Ward", in which he writes: "Ward Identities lie at the very foundations of renormalization."[5]

Andrei Sakharov said Ward was one of the "titans" of quantum electrodynamics alongside Dyson, Feynman, Schwinger, and Tomonaga.[6] In this regard, it has been said that physicists have made use of his principles and developments "often without knowing it, and generally without quoting him."[7]

Ward's probability amplitude for quantum entanglement

In a 1947 paper, published in Nature[8] (with Maurice Pryce), Ward was the first to calculate, and use, the probability amplitudes for the polarisation of two entangled photons moving in opposite directions.[9] For polarisations x and y, Ward derived this probability amplitude to be[10]

${\displaystyle \left|\psi \right\rangle =(\left|x,y\right\rangle -\left|y,x\right\rangle )}$

which once normalised can be expressed as.[9][11]

${\displaystyle \left|\psi \right\rangle ={1 \over {\sqrt {2}}}(\left|x\right\rangle _{1}\left|y\right\rangle _{2}-\left|y\right\rangle _{1}\left|x\right\rangle _{2})}$

where 1 and 2 refer to the two quanta propagating in different directions. Ward's probability amplitude is then applied to derive the correlation of the quantum polarisations of the two photons propagating in opposite directions.[8] This prediction was experimentally confirmed by Wu and Shaknov in 1950.[12] In current terminology this result corresponds to a pair of entangled photons and is directly relevant to a typical Einstein-Podolsky-Rosen (EPR) paradox, or situation, as explained by Dalitz and Duarte.[9][13][14]

It should be noted that, apparently following Dirac's doctrine, Ward was never bothered by issues of interpretation in quantum mechanics.[11]

Quantum statistics, Fermion theory, the Ising Model, Feynman diagrams, and Aldermaston

Ward made contributions to quantum mechanics,[10][15] fermion theory,[16] quantum solid-state physics,[17] and statistical mechanics and the Ising model.[18][19][20] His joint work, with Kac, on the Ising Model[18] gave rise to what is now being called the Kac-Ward operator.[21] He is further credited with being an early pioneer in the use of Feynman diagrams.[22]

In 1955–1956 Ward worked, at Aldermaston, on British atomic weapons and has been portrayed as the "creator of the British hydrogen bomb".[23] This topic is discussed by historian Lorna Arnold[24] while Ward's own account is given in his memoirs.[25] An additional analysis on this issue is provided by one of Ward's colleagues, and friend, Richard Dalitz, who wrote: "Ward had independently conceived a two-stage device".[13]

Standard Model

Ward is also one of the authors of the Standard Model of gauge particle interactions: his contributions were published in a series of papers he co-authored with Abdus Salam.[26][27][28][29] An insightful and well documented discussion on Ward's contribution to the physics of the Standard Model is given by Gordon Fraser in the book Cosmic Anger.[30] This topic is discussed further by Frank Close, who provides an illuminating perspective on the importance of Ward's contribution to the Standard Model.[5]

The contributions of Salam and Ward to the Standard Model were used in the development of the theoretical structure of the Higgs boson, as described by Higgs.[31]

Macquarie University

After World War II, Ward worked in several places in the United States and eventually he moved to Sydney, via New Zealand.[13] In 1964 he created the physics program of Macquarie University using the Feynman Lectures on Physics as primary textbooks. This program had a strong experimental emphasis and Ward himself (who originally was trained as an engineer) "had great admiration for anything practical".[32]

In the late 1970s Ward participated, with Frank Duarte, in the successful Macquarie science reform movement[33][34] and considered this a "most important accomplishment".[32]

Personal

Ward's total number of published papers was only about 20, a fact that reflects a strong sense of self-criticism. He was also critical of what he called "PhD factories" and expressed scepticism towards the importance being attached to large number of citations. Ward's "directness and frankness often got him at odds with managers and administrators."[35]

Besides his physics, Ward was an accomplished pianist and French horn player. Although a bachelor most of his life, he was briefly married while in the US. In Sydney, he lived at 10 Fern Street, in the northern suburb of Pymble.[35] He has an Erdős number of 2.

After death

In immediate correspondence following his death, Willis E. Lamb wrote "I greatly admired him and his work... I hope our paths cross again." Philip Anderson highlighted Ward's contribution to the Standard Model while indicating that he had communicated his passing to Freeman Dyson.[35] Ward's succinct unfinished memoirs were published in 2004.[36]

Ward's friends and co-authors

Luttinger's theorem (introduced by J. M. Luttinger and J. C. Ward) relates a Fermi liquid's particle density to the volume of its Fermi surface.

The one-loop correction to the vertex function. This is the dominant contribution to the anomalous magnetic moment of the electron.

References

1. ^ J. C. Ward (1950). "An identity in quantum electrodynamics". Phys. Rev 78: 182. Bibcode:1950PhRv...78..182W. doi:10.1103/PhysRev.78.182.
2. ^ Dalitz, Richard H.; Duarte, Frank J. (October 2000). "John Clive Ward" 53 (10): 99–100. Bibcode:2000PhT....53j..99D. doi:10.1063/1.1325207.
3. ^ F. J. Dyson, The S matrix in quantum electrodynamics, Phys. Rev. 75, 1736–1755 (1949).
4. ^ W. Greiner and J, Reinhardt, Quantum Electrodynamics, 4th Ed. (Springer, Berlin, 2009).
5. ^ a b F. Close, The Infinity Puzzle (Oxford University, Oxford, 2011).
6. ^ A. Sakharov, Memoirs (Knopf, New York, 1990).
7. ^ M. Dunhill, Professor John Clive Ward, in The Merton Record (Oxford University, Oxford, 1995).
8. ^ a b M. H. L. Pryce and J. C. Ward, Angular correlation effects with annihilation radiation, Nature 160, 435 (1947).
9. ^ a b c F. J. Duarte, The origin of quantum entanglement experiments based on polarization measurements, Euro. Phys. J. H 37, 311–318 (2012).
10. ^ a b J. C. Ward, Some Properties of Elementary Particles (D. Phil. Thesis, Oxford University, 1949).
11. ^ a b F. J. Duarte (2014). Quantum Optics for Engineers. New York: CRC. ISBN 978-1439888537.
12. ^ C. S. Wu and I. Shaknov, The angular correlation of scattered annihilation radiation, Phys. Rev. 77, 136 (1950).
13. ^ a b c R. H. Dalitz and F. J. Duarte, John Clive Ward, Physics Today 53 (10), 99–100 (2000).
14. ^ F. J. Duarte, The probability amplitude for entangled polarizations: an interferometric approach, J. Mod. Opt. 60, 1585-1587 (2013).
15. ^ E. W. Montroll and J. C. Ward, Quantum statistics of interacting particles; general theory and some remarks on properties of an electron gas, Phys. Fluids 1, 55–72 (1958).
16. ^ J. M. Luttinger and J. C. Ward, Ground-state energy and many-fermion system, Phys. Rev. 118, 1417–1427 (1960).
17. ^ J. C. Ward and J. Wilks, Second sound and the thermo-mechanical effect, Phil. Mag. 43, 48–50 (1952).
18. ^ a b M. Kac and J. C. Ward, A combinatorial solution of the two-dimensional Ising model, Phys. Rev. 88, 1332–1337 (1952).
19. ^ R. B. Potts and J. C. Ward, The combinatorial method and the two-dimensional Ising model, Prog. Theor. Phys. 13, 38–46 (1955).
20. ^ E. W. Montroll, R. B. Potts, and J. C. Ward, Correlations and spontaneous magnetization of the two-dimensional Ising model, J. Math. Phys. 4, 308–322 (1963).
21. ^ L. O. Chekhov, A spectral problem on graphs and L-functions, Russian Math. Surv. 54, 1197 (1999).
22. ^ D. Kaiser, Drawing Theories Apart: The Dispersion of Feynman Diagrams in Postwar Physics (University of Chicago, Chicago, 2005).
23. ^ J. V. Malheiros, Publico (Lisbon, 4 April 1992) pp. 2–6 in Portuguese.
24. ^ L. Arnold, Britain and the H-Bomb (Palgrave, New York, 2001).
25. ^ J. C. Ward, Memoirs of a Theoretical Physicist (Optics Journal, Rochester, New York, 2004) Chapter 8.
26. ^ A. Salam and J. C. Ward, Weak and electromagnetic interactions, Nuovo Cimento 11, 568–577 (1959).
27. ^ A. Salam and J. C. Ward, On a gauge theory of elementary interactions, Nuovo Cimento 19, 166–170 (1961).
28. ^ A. Salam and J. C. Ward, Electromagnetic and weak interactions, Phys. Lett. 13, 168–171 (1964).
29. ^ A. Salam and J. C. Ward, Gauge theory of elementary interactions, Phys. Rev. 136 B, 763–768 (1964).
30. ^ G. Fraser, Cosmic Anger (Oxford University, Oxford, 2008).
31. ^ P. W. Higgs, Spontaneous symmetry breakdown without massless bosons, Phys. Rev. 145, 1156–1163 (1966).
32. ^ a b
33. ^ B. Mansfield and M. Hutchinson, Liberality of Opportunity: A history of Macquarie University 1964–1989 (Hale and Iremonger, Sydney, 1992).
34. ^ J. C. Ward, Memoirs of a Theoretical Physicist (Optics Journal, Rochester, New York, 2004) Chapter 13.
35. ^ a b c
36. ^ J. C. Ward, Memoirs of a Theoretical Physicist (Optics Journal, Rochester, New York, 2004).