# Honorary fellows: Sir Thomas W B Kibble - Imperial College London

For his outstanding contributions to theoretical physics ranging from the theory of elementary particles to modern early-universe cosmology.

The unifying theme behind Tom Kibble’s work is the theory of non-abelian gauge theories. This is a wide-ranging generalisation of the gauge-invariance of Maxwell’s classical theory of electromagnetism and is a structure that is of fundamental importance in modern physics.

Kibble’s first work in this area concerned the application of these ideas to general relativity. In particular, he showed clearly how general relativity can be regarded as a gauge theory: a result that has had a major impact on subsequent attempts to construct a quantum theory of gravity.

Another important early piece of work was Kibble’s comprehensive resolution of the infrared problems that afflict the quantum theory of electromagnetism. This was of great importance in the construction of a coherent theory of quantum electrodynamics.

One of Kibble’s most important pieces of work, initially in collaboration with Gerald Guralnik and Carl Richard Hagen, was his study of the Yang-Mills extension of electromagnetism and, in particular, the mechanism whereby the basic particles in the theory can acquire a mass. This so-called “Higgs” mechanism lies at the heart of all the modern unified theories of fundamental particles and earned Kibble (jointly with Higgs) the prestigious Hughes Medal of the Royal Society in 1981.

This mechanism also predicts the existence of soliton-like solutions of the field equations. In 1976, Kibble realised that these structures could condense as the universe cooled from the hot conditions prevailing in the big-bang, and might therefore have striking effects on the development of large-scale structure in the universe. This idea triggered a massive theoretical and observational research programme that continues to the present time. Kibble’s vision has thereby provided an extraordinary link between the macroscopic and microscopic features of our universe. The correctness of Kibble's vision has been experimentally confirmed in the context of vortex formation in superfluid Helium 3. The new field of astroparticle physics has become one of the most important areas in which to probe the sub-nuclear structure of matter.