Addressing the Hubble and $S_8$ Tensions with a Kinetically Mixed Dark Sector

Understand

We present a kinetically mixed dark sector (KMIX) model to address the Hubble and $S_8$ tensions.

• Inspired from string theory, our model includes two fields: an axion, which plays a role similar to the scalar field in early dark energy models, and a dilaton.
• This theory differs from other axio-dilaton models aimed at the Hubble tension in that there is necessarily kinetic mixing between the two fields which allows for efficient energy transfer from the axion into the dilaton which has $w\approx1$.
• As a direct consequence of these dynamics, we find the model does not need to resort to a fine-tuned potential to solve the Hubble tension and naturally accommodates a standard axion potential.