On Soft Limits of Inflationary Correlation Functions
  Soft limits of inflationary correlation functions are both observationally
relevant and theoretically robust. Various theorems can be proven about them
that are insensitive to detailed model-building assumptions. In this paper, we
re-derive several of these theorems in a universal way. Our method makes
manifest why soft limits are such an interesting probe of the spectrum of
additional light fields during inflation. We illustrate these abstract results
with a detailed case study of the soft limits of quasi-single-field inflation.
