Robert Brout 1928–2011

Born in New York in 1928, Robert Brout obtained his PhD from Columbia University in 1953, before becoming an associate professor in Cornell and a well-established expert on statistical mechanics. There he met François Englert, who was visiting as a postdoctoral researcher; this was the beginning of a life-long scientific collaboration. In 1961 Brout took the bold step to resign his position at Cornell and move with his family to Brussels, where he eventually became professor at the Université Libre de Bruxelles, and co-directed with Englert the Service de Physique théorique.

In 1964, Brout and Englert started a revolution with a famous three-page article, which offered the possibility to give mass to vector gauge bosons, the vectors of fundamental interactions. It proved to be the key to the unification of the weak and electromagnetic interactions in the Standard Model. This short article described the mechanism in various contexts, offering different possible realizations (with or without a fundamental scalar, in a "spontaneous" or "dynamical way"). Shortly afterwards this work was complemented by Peter Higgs, using an alternative mathematical approach. The work was recognized by the European Physical Society prize, the Wolf prize, and later the Sakurai prize.

The Brout–Englert–Higgs mechanism was later established by the discovery of the Z and W bosons and by the detailed field-theoretic computations that confirm the electroweak theory within its suspected domain of validity. The goal of the LHC is to investigate its precise realization, either through finding a new, fundamental scalar boson or (for instance) through some other new dynamics.

It was characteristic of Brout’s attitude in physics to rely heavily on his intuition, often gained from his expertise in statistical mechanics (the above example is typical in this regard); the mathematical developments would then follow. He would often present his ideas with impressive gusto, mimicking enthusiastically the physical situations. His warm personality gained the admiration of many students, who later perpetuated his approach around the world.

In his personal life, he was close to nature. His devotion to gardening inspired the title of his festschrift, the "gardener of Eden", an expression that also conveys his gentlemanly manners in science and in life. He was clearly seduced by the European way of life and indeed eventually opted for Belgian nationality.

Brout produced invaluable contributions to diverse domains of theoretical physics. His basic paper on irreversibility in 1956 initiated the "Brussels School" approach to irreversible processes. His contributions to the statistical theory of phase transitions, to fundamental interaction physics and to cosmology address basic questions. His pioneering work in cosmology, in which the whole Brussels group was eventually involved, introduced what is now known as inflation and relates the exponential expansion to the emergence out of a quantum fluctuation of the universe, a scenario that may well turn out to be basically the correct one.

In the early 1970s, when quantum field theory and gauge theories started to revolutionize particle physics (in no small part as a result of his work), Brout undertook itinerant courses in the Belgian universities (notably Leuven and Louvain-la-Neuve). This teaching – and the exceptional warmth of his personality – had a strong influence on the respective theory groups, affecting successive generations of theorists to this day. For this reason, the loss of this fatherly figure is felt with sadness in the Belgian physics community, which he greatly helped to unify.

Robert Brout died on 3 May in his house, in Linkebeek, Brussels, a small heaven surrounded by the blossoming flower beds that he had planted.

François Englert and Jean-Marie Frère, Universitè Libre de Bruxelles.

William (Bill) Galbraith 1925–2011

In 1952, armed with a rubbish bin (painted black on the inside) from the UK Atomic Energy Research Establishment at Harwell, a recycled 25 cm searchlight mirror and a 5 cm phototube, Bill Galbraith and his colleague John Jelley set out to measure flashes of Cherenkov light in the night sky. They observed a count rate of about one pulse per minute, so confirming Patrick Blackett’s assertion that Cherenkov light from charged cosmic rays traversing the atmosphere should contribute to the overall night-sky intensity. In 1953, with improved apparatus at the Pic du Midi, the pair successfully demonstrated that the light signals they recorded had the polarization and spectral distribution characteristic of Cherenkov radiation. These experiments also revealed the correlation of the amplitude of the light signal with shower energy. The first steps towards Cherenkov astronomy had been taken.

Born in Renfrew, Scotland, Bill left school at the outbreak of the Second World War. His passion for science and engineering resulted in his working as a student assistant in the research laboratories of GEC. His BSc from Birkbeck College, the University of London, was achieved via study at evening classes, while his "day job" involved the development of pre-production versions of vacuum tubes for airborne and naval radar. Bill then joined the nuclear physics division at Harwell in 1948, measuring spontaneous fission rates of uranium and plutonium isotopes. This led to a PhD as an external student at the University of London.

After moving to the Lawrence Radiation Laboratory in 1958, Bill worked on K → μ decay at the Berkeley Bevatron. Upon his return to the UK he was involved in the construction and operation of NIMROD, the 7 GeV proton synchrotron for the newly-established Rutherford High Energy Laboratory. He also worked at CERN and Brookhaven on CP violation in K0 decay, observations that narrowly post-dated and confirmed work by James Cronin and Val Fitch. Bill was appointed chair of high-energy physics at the University of Sheffield in 1966, where he worked in collaborations at the UK Daresbury Laboratory – where he was one of the founders of research activities using the newly constructed NINA electron synchrotron – and on a series of experiments in the West Area at CERN using the Omega Spectrometer.

Bill was an excellent mentor of undergraduates, postgraduates and young academics. His sense of fair play earned him great respect among his university peers and he was appointed as dean of faculty of pure science and served as a pro-vice-chancellor shortly before his retirement.

Music played a great part in Bill’s life, from participation in choral societies in both Wantage and Sheffield to a love of attending concerts. He and his wife Elizabeth were keen supporters of the arts in general and music in particular. In Sheffield, Bill’s influence in his support of activities, such as the Sheffield Festival and of local musicians including the Lindsay String Quartet and Opera North promoted the city’s status as a centre for arts and music.

Lee Thompson, the University of Sheffield, on behalf of Bill’s colleagues and friends.