Cosmological Constraints on Interacting Scalar-Field Dark Matter and Early Dark Energy mediated by a Kinetic Kernel

Abstract

In this work, we build a general framework for constraining interacting scalar fields with cosmological observations, applicable to a broad family of scalar--field potentials and interaction kernels. As a representative example, we derive constraints on a model in which dark matter is described by a scalar field $\varphi$ with a quadratic potential and dark energy by a scalar field $\psi$ with the Albrecht--Skordis potential, considering both the uncoupled case and a more general scenario in which the exchange of energy occurs through an interaction kernel proportional to the kinetic energies of the scalar fields $Q\propto {\dot{\varphi }}^2{\dot{\psi }}^2$. The scalar field parameters are constrained by using \textit{Planck} 2018 CMB data, DESI BAO measurements, Ly-$\alpha$ forest constraints, and SNeIa observations, and we find that the scalar field parameters are driven toward their $\Lambda$CDM-like limits; the early dark energy fraction is largely suppressed, and the SFDM mass is bounded to values for which the field behaves close to cold dark matter. In the interacting case, the results show no significant preference for the transfer of energy between dark energy and dark matter at 95\% C.L. In general, the model keeps $H_0$ close to the Planck-$\Lambda$CDM range and provides best-fit ${\chi }^2$ values comparable to those of the corresponding $\Lambda$CDM fits.

12 pages, 7 figures