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Department of Physics

The Cavendish Laboratory
Professor Sir Sam Edwards CBE FRS

It is with great sadness that we report the death of Professor Sir Sam Edwards, Cavendish Professor Emeritus of Physics and a Fellow of Gonville & Caius College.  He  died on 7 May 2015, aged 87.

An undergraduate of Gonville and Caius College, Sam carried out his PhD under Julian Schwinger at Harvard University on the structure of the electron, which involved using the techniques of quantum field theory.  Seeking challenges outside particle physics, he realised that he could apply the techniques of quantum field theory to complex problems in condensed matter physics.  His seminal paper entitled A new method for the evaluation of electric conductivity in metals opened up a vast field of research in the quantum mechanics of electrons in random potentials.  As David Khmelnitskii has written,

‘Sam Edwards, then at Birmingham, was introduced to the problem by Peierls and made the decisive step by considering the transport of electrons elastically scattered by a random potential.  This step had dual importance: first of all, Edwards came up with a field theory, which corresponded to averaging over random potentials; secondly, he developed a very effective diagrammatic technique, which allowed him to calculate the Drude conductivity and gave to those who came after him an efficient tool for further research’

In the subsequent years prior to his arrival in Cambridge, he published innovative papers on The statistical dynamics of homogeneous turbulence (1964), The statistical mechanics of polymers with excluded volume (1965), The  theory of polymer solutions at intermediate concentration (1966) and Statistical mechanics with topological constraints (1968).

The theoretical activity in the Cavendish received an enormous boost in 1972 with his appointment as John Humphrey Plummer Professor of Physics, which he chose to hold in the Laboratory.   He brought quite new dimensions and directions to both the theoretical and experimental work of the Laboratory.  As stated in the book Stealing the Gold: A Celebration of the Pioneering Physics of Sam Edwards (2004),

‘Over the course of nearly half a century, Sam Edwards has led the field of condensed matter physics into new directions, ranging from the electronic and statistical properties of disordered materials to the mechanical properties of granular materials. Along the way, he has provided seminal contributions to fluid mechanics, polymer science, surface science and statistical mechanics.’

Among his major contributions was the expansion of the range of theoretical and experimental work in polymer science and statistical physics. In order to encompass this expansion of the scope of the Solid State Physics Group, it was renamed the Theory of Condensed Matter (TCM) Group, thus incorporating polymer and complex fluids into its interests.

Almost immediately, however, on 1 October 1973, Sam became Chairman of the Science Research Council, a position he was to hold for four years.  Nonetheless, he continued supervise his graduate students throughout this period, which saw some of his most original contributions to Condensed Matter Theory.  Of particular importance was the theory of spin glasses which he developed with Anderson in 1975.  He employed the technique known as the replica trick, which he had already used in his study of polymers, to work out the ground state and properties of spin glasses.  As Heine expresses it, `A whole industry on spin glasses and then neural networks developed'.

Edwards' second major contribution during this period was the theory of the dynamics of polymers, the process known as reptation, with Masao Doi. Entangled long chain molecules wiggle as if they were confined to a tube, the motion consisting of extending out one end of the tube and retracting at the other.  The dynamics of reptation described by their theory proved to be very successful and now underpins the huge, industrially important field of rheology.  The summation of their pioneering work was published in their influential book The Theory of Polymer Dynamics (1986).

What is remarkable is that Sam made these fundamental contributions to theoretical physics, while carrying out his responsibilities as chairman of the Science Research Council in London.  He would supervise research students on the train and worked out multi-dimensional integrals during meetings, filling up successive `little red books'.

During his early years in the Cavendish he brought new theoretical initiatives to the TCM group which were to prove to be major growth areas.  In particular, he realised the need to make full use of his industrial connections to support theoretical physics activities.  The Industrial CASE award scheme provided opportunities for some outstanding graduate students to study with Edwards -- they were to become staff members in due course.  These included Robin Ball, Mark Warner and Michael Cates.  Other graduate students included Richard Needs and Tom McLeish.

Sam was appointed Cavendish Professor in 1984 in succession to Brian Pippard and took on the role of Head of Department for the next five years. He had by then acquired vast experience of national and international science politics.  He had served as a member of the Council of the European Physical Society from 1969-71.  He had been a member of various committees of the Science Research Council since 1968 and of the Council's Science Board since 1970. In 1971 he was appointed a member of the University Grants Committee and was then Chairman of the Science Research Council from 1973 to 1977. This was followed by his Chairmanship of the Defence Scientific Council from 1977-80 and Chief Scientific Adviser to the Department of Energy from 1983 to 1988.  He had also served as Vice-President of the Royal Society, of the Institute of Physics and had been the President of the Institute of Mathematics.  Thus, he had a very wide range of contacts in government and industry and used that experience to begin a major expansion of the scope of the Laboratory's activities.

He was to exploit his industrial contacts with remarkable effect.  He was famous for hosting dinners for senior figures in industry and government in Caius College, where he had accumulated a superb, and large, wine collection.  When I took over as the Head of the Cavendish in 1997, his only advice to me was ‘Have dinners!’

Sam realised that the Government and the Research Councils could not be relied upon to provide the resources for new activities.  Rather, the way to do new things was to become much more closely associated with the needs of industry and to enhance the support they could provide to the research programme.  This was also attractive to Government who were keen to promote research which would be of benefit to industry.  Often, matching funding from the research councils and government could be obtained, as well as studentships through a variety of incentive schemes.   During Sam’s five-year period as Head of Department new groups were created in Microelectronics led by Haroon Ahmed (1983), Semiconductor Physics by Michael Pepper (1984), Optoelectronics by Richard Friend (1987), Polymers and Colloids by Athene Donald (1987) and the Interdisciplinary Centre for High Temperature Superconductivity, a collaborative effort between a number of departments (1987) - all of these new activities were to have strong industrial connections. 

Sam’s contributions to the Cavendish and to physics in general were immense. And through it all he remained affable, approachable and a friend to all his colleagues and students.  I remember vividly his love of opera where we often bumped into him and his wife.  I especially remember his great affection for Janacek’s Cunning Little Vixen, one of the most touching and humane operas in the repertory. 

Sam will be greatly missed.  Our thoughts are with his wife and family.

Malcolm Longair.