The role of the auxiliary scalar field φ in Brans-Dicke theory is discussed. If a constant vacuum energy is assumed to be the origin of dark energy, then the corresponding density parameter would be a quantity varying with φ; and almost all of the fundamental components of our universe can be unified into the dynamical equation for φ. As a generalization of Brans-Dicke theory, we propose a new ...

A quantum correction to the Brans-Dicke theory due to interactions among matter fields is calculated, resulting in violation of WEP, hence giving a constraint on the parameter ω far more stringent than accepted so far. The tentative estimate gives the lower bounds > ∼106 and > ∼108 for the assumed force-range > ∼1m and > ∼1AU, respectively. E-mail: [email protected] Many aspects o...