Accommodate Whittaker propagators for spinning exchanges

Determine whether the numerical framework based on Witten–Feynman parameterization and the reduced Schwinger method can accommodate the more complex Whittaker-function propagator arising in cosmological collider scenarios with spinning exchanges and chemical-potential-type interactions.

Background

The paper develops and validates a numerical framework for scalar one-loop de Sitter correlators, using Witten–Feynman parameterization to convert the diagrams into generalized Euler–Mellin integrals and the reduced Schwinger method to analytically integrate the most oscillatory common-scale direction. The discussion proposes extending this framework beyond scalar exchanges to massive vectors, fermions, spin-2 fields, and other spinning matter.

In scenarios involving chemical potentials, the relevant bulk propagators are more complicated Whittaker functions rather than the scalar propagators treated explicitly in the paper. Such extensions could generate distinctive squeezed-limit bispectrum signatures, but the paper does not establish whether its integration framework remains applicable to these propagators; it explicitly leaves this compatibility question for future work.