Dark Energy From the Gravitational Wave Background With Scalar Field Dark Matter

Abstract

Recent observational results, such as those from pulsar timing arrays (PTA), suggest a low-frequency Gravitational Wave Background (GWB) permeates our universe. This opens the possibility that gravitational waves could span a broader spectrum, potentially impacting cosmological scales. Among novel Dark Energy (DE) models that explain DE as a very low-frequency GWB, the Compton Mass Dark Energy model (CMaDE) has shown promising theoretical alignment with cosmic acceleration. In this study, we explore the cosmological implications of the CMaDE model when coupled with Scalar Field Dark Matter (SFDM) as the dark matter candidate. We numerically solve the cosmological evolution equations for this combined CMaDE+SFDM framework, examining its impact on key observables and comparing results to the standard $\mathrm{\Lambda CDM}$ model. Our findings demonstrate that the CMaDE+SFDM model is broadly consistent with $\mathrm{\Lambda CDM}$, showing similar evolution in observables such as the cosmic microwave background and the background energy densities, with some deviations that merit further investigation.