Not by accident

The Sixties in Berkeley were exciting times for a young graduate student, not just because of the free speech movement, but also in elementary particle physics. The strong nuclear interactions appeared to be so different from the beautiful simplicity of QED that a systematic programme was underway to find a new foundation to relativistic quantum interactions. A new set of axioms was sought in the so-called S-matrix programme by abstracting properties of analyticity and unitarity exhibited in Feynman diagrams without recourse to an underlying local field theory. Remarkably this ambitious programme, guided by copious experimental data for hadronic scattering, did result in an alternative solution, now referred to as ‘string theory’. The fact that the nuclear or strong interaction was subsequently formulated by QCD, a local field theory, should not obscure this remarkable discovery. Only recently, with the advent of Maldacena's conjectured AdS/CFT correspondence between string and gauge field theory [Ma198], are we beginning to understand why two alternative solutions to strong interactions (gauge theory and its dual string theory) should co-exist as correct and equivalent theories. Whether string theory ultimately leads to a fundamental string/gauge duality for all forces including gravity, is not clear yet. Nevertheless the discovery of the theory, contrary to a widespread opinion, was not by accident, but was the result of the traditional interaction between theoretical ideas and experimental data.

Here let me give an intentionally anecdotal description of my recollections of early developments in string theory.