`Consistency of higher spin interactions'

Abstract:
For a long while the domain of but a few hardy enthusiasts, higher spin (HS)
gauge theory has recently undergone something of a renaissance, thanks to its
importance in understanding certain "quantum" aspects of string
theory. Although we have known for a long time the free theory of HS gauge
fields, the question of how to add interactions is a fairly nontrivial one. In
this talk I will briefly outline how such interaction terms can be derived
using the BRST approach, and then move on to issues of consistency
above-and-beyond gauge invariance. For massless HS theories, this involves
looking at quartic and higher-order interactions and properties of the
S-matrix. For massive theories, one needs to overcome the Velo-Zwanziger
problem, which says that gauge invariance alone is not enough to ensure causal
propagation of the degrees of freedom.