Cosmic acceleration driven by dark matter self-interactions: A phenomenological treatment

We explore the idea that cosmic acceleration may be a byproduct of late-time effects like structure formation in two steps. First, we consider the equation of state for an inhomogeneous cosmic fluid, which may lead to a Gedanken-model for cosmic evolution, where dark matter is strongly self-interacting and stays in a plasma state until late stages of the cosmic evolution. After decoupling, it condensates to super-structures with cosmic voids similar to the current picture of the universe, introducing a negative pressure term in relation to self-interaction strength. Secondly, we carry out a cosmological analysis inspired by this scenario via a phenomenological ansatz that exhibits a transient behavior. In this analysis, we use the recent Type Ia supernova compilation and high redshift quasar data and compare the results to that of $\Lambda$CDM. It turns out that proposed model can solve the quasar Hubble diagram tension.