Continuous Spectrum on Cosmological Collider

Understand

We study the effects of a massive field with a continuous spectrum (continuum isocurvaton) on the inflationary bispectrum in the squeezed limit.

• As a concrete example, we extend the quasi-single field inflation model to include a continuum isocurvaton with a well-motivated spectral density from extra dimensions and focus on a contribution to the bispectrum with a single continuum isocurvaton exchange.
• In contrast to the usual case without the continuous spectrum, the amplitude of the bispectrum has a damping feature in the deep squeezed limit, which can be strong evidence for the continuous spectrum.