Gazing into the dark sector interactions through cosmological observables

概要

Cosmological observables provide powerful probes of physics beyond the Standard Model across a wide range of energy scales. In this talk, I will discuss how processes from different epochs of the early universe can leave observable imprints on key cosmological quantities. The annihilation of dark matter into neutrinos after neutrino decoupling, around the MeV scale or below, and the decoupling of light degrees of freedom from the thermal bath at a few hundred MeV or higher, can both influence the effective number of relativistic species, $\Delta N_{\rm eff}$. At much higher scales, post-inflationary dynamics, such as the production of dark matter or supermassive right-handed neutrinos, can affect the scalar spectral index, $n_s$. Together, these connections illustrate how cosmological measurements, spanning from the MeV scale to the inflationary epoch, can reveal signatures of new physics far beyond the reach of laboratory experiments.

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