The gravitational wave contribution to the cosmic microwave background anisotropies

We study the possible contribution of a stochastic gravitational wave backg round to the anisotropy of the cosmic microwave background (CMB) in cold an d mixed dark matter models. We test this contribution against recent detect ions of CMB anisotropy at large and intermediate angular scales. Our likeli hood analysis indicates that models with blue power spectra (n similar or e qual to 1.2) and a tensor-to-scalar quadrupole ratio of R = C-2(T)/C-2(S) s imilar to 2 are most consistent with the anisotropy data considered here. W e find that by including the possibility of such a background in the CMB da ta analysis, it can drastically alter the conclusion of the remaining cosmo logical parameters.