Supergravity: A Post-Einstein Unification
In attempting to honor the memory of Einstein’s work on this centennial occasion, it seems most fitting to discuss a current incarnation of his lifetime goal, unification of gravity and matter. As we all know, earlier attempts lay partly in inclusion of the other classical gauge field, electromagnetism, and partly in relating classical particles to singularities in the field. With the proliferation of new gauge fields and matter particles, especially the non-classical fermions, this program lost much of its immediate attraction. But the spirit of his quest always remained very much alive and unification is more than ever a guiding principle in physics, though mostly to the (temporary) exclusion of gravity. It is therefore gratifying that unified models with gravity as a basic ingredient have also begun to flourish and I shall devote myself to a discussion of one of these, supergravity,1 which is by now almost three years old. Its relevance to the real world is as yet unclear, but it is an elegant new gauge theory from which much has been, and is still to be, learned. I will try to show that it is simple, natural and unique in the same way that bosonic gauge theories are. The approach I will use is in fact equally applicable there and really uses only two underlying concepts: the initial restrictions imposed on sources of massless free fields of higher (S ≥ 1) spin and the necessity for self-interaction where those fields are themselves grouped in (global) gauge multiplets. Details of the work, carried out in collaboration with D. Boulware and J. H. Kay, may be found in a forthcoming paper2 where earlier references are also listed.
KeywordsGauge Field Bianchi Identity Free Action Pure Helicity Global Invariance
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