Axion Isocurvature Collider

Understand

Cosmological colliders can preserve information from interactions at very high energy scale, and imprint them on cosmological observables.

• Taking the squeezed limit of cosmological perturbation bispectrum, information of the intermediate particle can be directly extracted from observations such as cosmological microwave background (CMB).
• Thus cosmological colliders can be powerful and promising tools to test theoretical models.
• In this paper, we study extremely light axions (including QCD axions and axion-like-particles), and consider them constituting cold dark matter (CDM) at late times.