Revisiting cosmological diffusion models in Unimodular Gravity and the $H_0$ tension

Understand

Within the framework of Unimodular Gravity, we consider non-gravitational interactions between dark matter and dark energy.

• Particularly, we describe such interactions in the dark sector by considering diffusion models that couple the cold dark matter fluid with the dark energy component, where the latter has the form of a variable cosmological "constant".
• For the first time, we solve the cosmological evolution of these models from the radiation dominated era to the present day.
• We show how the diffusion processes take place by analyzing the cosmological evolution of the energy density parameters $\Omega_{cdm}$ and $\Omega_{\Lambda}$, as well as that of the Hubble parameter.