Quenched Cosmological Collider Physics: Random fields & white noises

Abstract

We study a massive spectator field in de Sitter space coupled linearly to a spatially quenched random source with a deterministic power-law time profile. For arbitrary temporal weight, the fixed-realization problem is exactly solvable in terms of Lommel functions, while a Mellin--Barnes representation separates the analytic forced response from the homogeneous massive completion. After Gaussian disorder averaging, the random field modifies only the statistical sector of the propagator, leaving the spectral function and heavy-field poles unchanged. The resulting cosmological-collider seed factorizes exactly into one generalized hypergeometric sector associated with the forced response and two Gauss hypergeometric branches carrying the massive signal, with cancellation of the nonanalytic folded contribution. A persistent source produces a local late-time logarithm in the bispectrum sector, whereas any decaying source renders the physical Schwinger--Keldysh endpoint integrable. For sufficiently fast decay, the nonanalytic massive clock becomes parametrically dominant in the squeezed limit. For spatial white noise, the crossover also removes the explicit exchanged-scale dependence of the disorder contribution and allows destructive interference with the original collapsed trispectrum collider branch. More generally, the temporal profile controls the clock envelope, amplitude, and phase while leaving its logarithmic frequency fixed by the heavy-field mass.