Kinetically Coupled Scalar Fields Model and Cosmological Tensions

TL;DR

This paper proposes a kinetically coupled scalar fields model combining early dark energy and scalar field dark matter to address cosmological tensions, especially the Hubble tension, while analyzing its effects on large-scale structure.

Contribution

It introduces a new coupled scalar fields model that partially alleviates the large-scale structure tension and provides constraints on the coupling constant using MCMC methods.

Findings

The model yields a non-zero coupling constant of approximately 0.03.

It resolves the Hubble tension by increasing the Hubble constant to about 72.4 km/s/Mpc.

The model results in a higher $S_8$ value, similar to EDE, but slightly reduced compared to EDE alone.

Abstract

In this paper, we investigate the kinetically coupled early dark energy (EDE) and scalar field dark matter to address cosmological tensions. The EDE model presents an intriguing theoretical approach to resolving the Hubble tension, but it exacerbates the large-scale structure tension. We consider the interaction between dark matter and EDE, such that the drag of dark energy on dark matter suppresses structure growth, which can alleviate large-scale structure tension. We replace cold dark matter with scalar field dark matter, which has the property of suppressing structure growth on small scales. We employed the Markov Chain Monte Carlo method to constrain the model parameters, our new model reveals a non-zero coupling constant of $0.030 \pm 0.026$ at a 68% confidence level. The coupled model yields the Hubble constant value of $72.38^{+0.71}_{-0.82}$ km/s/Mpc, which resolves the Hubble tension. However, similar to the EDE model, it also obtains a larger $S_8$ value compared to the $\Lambda$CDM model, further exacerbating the large-scale structure tension. The EDE model and the new model yield the best-fit values of $0.8316$ and $0.8146$ for $S_8$, respectively, indicating that the new model partially alleviates the negative effect of the EDE model. However, this signature disappears when comparing marginalised posterior probabilities, and both models produce similar results. The values obtained from the EDE model and the new model are $0.822^{+0.011}_{-0.0093}$ and $0.819^{+0.013}_{-0.0092}$, respectively, at a 68% confidence level.