Neutrinos as a probe of curvature

Neutrinos, as the anisotropic stress tensor, have a damping effect on tensor mode perturbation from inflation to Λ dominated era. First, we study squared amplitude reduction for wavelength entering horizon during radiation and matter-dominated phases in negatively curved de Sitter spacetime. Then, by comparing with other spatial spacetimes, K=0 K=1, highest difference between closed open cases is seen Thus, neutrinos can be added another candidate determining nature of space-time.