Unified Superfluid Dark Sector
  In this talk I present a new model of a unified dark sector, where late-time
cosmic acceleration emerges from the dark matter (DM) superfluid framework. We
will start by reviewing the dark matter superfluid model and show how it
describes the dynamics of DM in large and small scales. Then we will show that
if the superfluid consists of a mixture of two distinguishable states with a
small energy gap, such as the ground state and an excited state of DM,
interacting through a contact interaction a new dynamics of late-time
accelerated expansion emerges in this system, without the need of dark energy,
coming from a universe containing only this two-state DM superfluid. I will
show the expansion history and growth of linear perturbations, and show that
the difference in the predicted growth rate in comparison to $\Lambda$CDM is
significant at late times.
