Alleviating cosmological tensions with a coupled scalar fields model

In this paper, we investigate the interaction between early dark energy (EDE) and scalar field dark matter, proposing a coupled scalar fields model to address the Hubble tension and S₈ tension. While the EDE model successfully alleviates the Hubble tension, it exacerbates the S₈ tension. To mitigate the negative impact of EDE, we introduce the interaction between EDE and dark matter. Specifically, we replace cold dark matter with scalar field dark matter, given its capability to suppress structure growth on small scales. We constrained the new model using cosmological observations including the temperature and polarization anisotropy power spectra data of cosmic microwave background radiation from Planck 2018 results, baryon acoustic oscillations measurements extracted from 6dFGS, SDSS, and BOSS, the Pantheon sample of type Ia supernovae, the local distance-ladder data (SH0ES), and the Dark Energy Survey Year-3 data. Employing the Markov Chain Monte Carlo method, we find that this novel model yields best-fit values of H₀ and S₈ equal to 71. 13 km/s/Mpc and 0. 8256, respectively. Compared to the model, the new model alleviates the Hubble tension but still fails to resolve the S₈ tension. However, we obtain a smaller value of S₈ compared to the result of 0. 8316 obtained for EDE model, which mitigates to some extent the shortcoming of the EDE model.