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

## TL;DR

This paper proposes a model where dark matter self-interactions lead to negative pressure effects, potentially explaining cosmic acceleration and resolving quasar Hubble diagram tension, through a phenomenological approach inspired by structure formation.

## Contribution

It introduces a novel scenario linking dark matter self-interactions to cosmic acceleration, supported by a phenomenological analysis fitting supernova and quasar data.

## Key findings

- Model fits supernova and quasar data well
- Resolves quasar Hubble diagram tension
- Suggests dark matter self-interactions influence cosmic acceleration

## Abstract

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.