S. Ferrara (CERN), D. Freedman (MIT), and P. van Nieuwenhuizen (Stony Brook) will receive the Special Breakthrough Prize in Fundamental Physics for their discovery of supergravity, which was published in 1976 in Phys. Rev. D. Supergravity is an extension of Einstein’s gravity which respects the three years earlier formulated concept of supersymmetry and was hugely influential in the development of particle physics and string theory over the last forty years.
Soon after the concept of supersymmetry, which assigns a super-partner to each known particle (super-bosons for fermions and super-fermions for bosons) was introduced in particle physics, Ferrara, Freedman, and van Nieuwenhuizen started to think about making this symmetry local and thus extending it to include gravity. At that time gravity, which meant General Relativity, was not on the minds of the majority of particle physicists since its force is too weak to be relevant for high energy experiments in particle colliders. The three physicists had to invent, reinvent and learn many of the mathematical concepts, like spinors in curved space and torsion, that were quite alien to most particle physicists at the time but were needed to even write down an ansatz for a possible supergravity theory.
The work began at the Ecole Normale Superieure in Paris, where Freedman was on a mini-sabbatical from the Institute for Theoretical Physics at Stony Brook. There he met Ferrara and the first step toward supergravity was taken. Van Nieuwenhuizen joined the effort when Freedman returned to Stony Brook. Several months of hard labor were needed to modify the starting point and show that the theory is supersymmetric, i.e. invariant under transformations that exchange bosons (the graviton in this case) and fermions, namely the newly introduced particle called gravitino which has spin 3/2.
The precise form of the Lagrangian and supersymmetry transformation rules emerged, its structure completely fixed by basic geometric and symmetry principles. If nature or mathematics would allow for (a minimal) supergravity to exist it had to be of this or an equivalent form. Many cancelations in the transformation of the theory, required for being supersymmetric, were established, but the final step was too complicated for the analytic methods the group used. In the end, 2,000 independent terms with integer coefficients were required to cancel. So van Nieuwenhuizen wrote a Fortran program to run on a computer at the Brookhaven Lab. Late one night the results for the coefficients of these terms slowly dribbled in through a modem to appear on a monitor in Stony Brook. Indeed, they all vanished. The theory was fully supersymmetric.
The paper was submitted on March 29, 1976, to Phys. Rev. D. and published in the June 15 edition of the monthly published volume (read it here). Since then supergravity has been developed into many directions (nearly 15,000 published papers with supergravity in their title or as a keyword). Its influence on modern theoretical physics and mathematics is clear, but extensive searches for superpartners such as the gravitino have come up empty-handed fo far.
-Robert Wimmer
