Exceptional Seminar Paolo Di Vecchia (NBI/Nordita)
room GO Jones LG7
In this talk we will discuss how gauge invariance fixes the soft behavior of massless particles as photons, gluons, gravitons, dilatons and Kalb-Ramond field. We will then check these results in string theory and we will show that the subsubleading behavior for gravitons includes string corrections in the bosonic and heterotic strings, but not in superstring. They are consequence of the fact that the three-graviton amplitude has string corrections with respect to the field theoretical one. It turns out, instead, that the soft behavior of the dilaton has no string corrections and, in particular, involves the generators of dilatations and special conformal transformations. We then study the soft behavior of the Goldstone boson, called in the literature also dilaton, that one gets when one breaks spontaneously the conformal symmetry and we show that its soft behavior is very similar, but not identical, to that of the string dilaton.