Natural inflation with a nonminimal coupling to gravity

摘要: Although natural inflation is a theoretically well-motivated model for cosmic inflation, it in tension with recent Planck microwave background anisotropy measurements. We present way to alleviate this by considering very weak nonminimal coupling of inflaton field gravity, both contexts metric and Palatini formulations gravity. start generic forms function, then take its simplest form do phenomenological analysis. Our results show that such an extension can render inflation's predictions good agreement the data. As long as inflaton's Ricci scalar $|\xi|\sim 10^{-3}$ symmetry breaking scale $f\gtrsim 2.0 M_{\mathrm{pl}}$, stay inside $68\%$ CL allowed regions until $f$ growing up $7.7 only $95\%$ region when exceeds value. The from theories are similar due simple function we use small magnitude $\xi$. Successful reheating also be realized model.