Planck constraints on inflation in auxiliary vector modified f(R) theories


PHYSICAL REVIEW D, cilt.92, 2015 (SCI İndekslerine Giren Dergi) identifier identifier


We show that the universal alpha-attractor models of inflation can be realized by including an auxiliary vector field A(mu) for the Starobinsky model with the Lagrangian f(R) = R + R-2/(6M(2)). If the same procedure is applied to general modified f(R) theories in which the Ricci scalar R is replaced by R + A(mu)A(mu) + beta del(mu)A(mu) with constant beta, we obtain the Brans-Dicke theory with a scalar potential and the BransDicke parameter omega(BD) = beta(2)/4. We also place observational constraints on inflationary models based on auxiliary vector modified f(R) theories from the latest Planck measurements of the cosmic microwave background anisotropies in both temperature and polarization. In the modified Starobinsky model, we find that the parameter beta is constrained to be beta < 25 (68% confidence level) from the bounds of the scalar spectral index and the tensor-to-scalar ratio.