Gravitational wave background in modified gravity dark energy models

Masaaki Morita, Hirotaka Takahashi

We study cosmological gravitational waves in dark energy models based on f(R)-modified gravity. Power spectra of both scalar-type and tensor-type perturbations are presented with emphasis on the difference from Einstein's gravity. We particularly explore how scalar-type gravitational waves are associated with matter perturbations, and discuss their observational consequences, leading to additional constraints on f(R)-modified gravity theories.