Cosmological implications of electromagnetically interacting dark matter: milli-charged particles and atoms with singly and doubly charged dark matter

Understand

While the behavior of the dominant component of the dark matter is reasonably well established by cosmological observables, its particle nature and interactions with the rest of the matter are not known.

• We consider three dark matter models that admit electromagnetic interaction between baryons and dark matter: (a) milli-charged particle (CCDM) of charge $q_{\rm ccdm}$ and mass $m_{\rm ccdm}$, (b) a neutral atom of two charged particles of mass $m_{\rm dd}$ (DD), and (c) a neutral atom of doubly charged particle and helium nucleus (HeD).
• We derive and discuss in detail the formation, stability, and interaction of these atoms with baryons.
• We derive the implications of this new interaction in the tight-coupling approximation, which allows us to analytically gauge their impact on the matter power spectrum and CMB anisotropy.