Feynman-like Rules for Calculating n-Point Correlators of the Primordial
  Curvature Perturbation
  A diagrammatic approach to calculate n-point correlators of the primordial
curvature perturbation \zeta was developed a few years ago following the spirit
of the Feynman rules in Quantum Field Theory. The methodology is very useful
and time-saving, as it is for the case of the Feynman rules in the particle
physics context, but, unfortunately, is not very well known by the cosmology
community. In the present work, we extend such an approach in order to include
not only scalar field perturbations as the generators of \zeta, but also vector
field perturbations. The purpose is twofold: first, we would like the
diagrammatic approach (which we would call the Feynman-like rules) to become
widespread among the cosmology community; second, we intend to give an easy
tool to formulate any correlator of \zeta for those cases that involve vector
field perturbations and that, therefore, may generate prolonged stages of
anisotropic expansion and/or important levels of statistical anisotropy.
Indeed, the usual way of formulating such correlators, using the Wick's
theorem, may become very clutter and time-consuming.
