Scalar Field as Dark Matter and Machian Cosmological Solution in the Generalized Scalar-Tensor Theory of Gravitation

The Machian cosmological solution satisfying $\phi =O(\rho /\omega)$ in the generalized scalar-tensor theory of gravitation with the varying cosmological constant is summarized. The scalar field $\phi $ with the exponential potential is introduced as dark matter and the barotropic evolution of matter in the universe is discussed. As the universe expands, the coefficient $\gamma $ of the equation of state approaches to -1/3 and the coupling function $\omega (\phi)$ diverges to $-\infty $.