Interacting Scalar Fields as Dark Energy and Dark Matter in Einstein scalar Gauss Bonnet Gravity

Abstract: A Gauss-Bonnet (GB) coupled scalar field $\phi$, responsible for the late-time cosmic acceleration and interacting with a coherent scalar field $\psi$ through an interaction potential $W(\phi,\psi)$, is considered from the point of view of particle physics for two different models. The non-minimal coupling between the GB curvature term and the field $\phi$ leads to a time-dependent speed of gravitational waves (GWs), which is fixed to unity in order to be consistent with current GW observations, rendering the GB coupling function model-independent. We investigate the dynamical stability of the system by formulating it in the form of an autonomous system, and constrain the model parameters using various sets of observational data. We find that both models are physically viable and closely follow the $\Lambda$CDM trend. We also use the updated Roman mock high redshift data to further constrain the parameters of the two models.