Large Spin-2 Signals at the Cosmological Collider
  We study the theory and phenomenology of massive spin-2 fields during the
inflation with nonzero background chemical potential, and extend the
cosmological collider physics to tensor modes. We identify a unique dimension-5
and parity-violating chemical potential operator for massive spin-2 fields,
which leads to a ghost-free linear theory propagating one scalar mode and two
tensor modes. The chemical potential greatly boosts the production of one
tensor mode even for very heavy spin-2 particles, and thereby leads to large
and distinct cosmological collider signals for massive spin-2 particles. The
large signals show up at the tree-level in both the curvature trispectrum and
the tensor-curvature mixed bispectrum.
