| Hybrid models of inflationary cosmology provide a compelling framework in which both primordial inflation and gauge symmetry breaking can be achieved. The supersymmetric realization of hybrid inflation is naturally tied to the scale of grand unified theories, and may be driven by radiative (quantum) corrections alone. Despite the simple elegance of this model, it is incomplete, and further corrections from sources such as supergravity should be included. Indeed, in anticipation of the precision cosmological data now being collected by the Planck satellite, these and other well-motivated contributions may play an important role in comparing the model with the new observations. In the context of minimal supergravity (i.e. canonical Kahler potential), we show that the application of soft supersymmetry-breaking corrections can reduce the scalar spectral index, ns, to better agree with WMAP measurements. In fact, the predictions span the entire 2σ range around the current WMAP central value of ns = 0.968. However, the values of another important parameter, the tensor-to-scalar ratio r, are too small with minimal Kahler to be observed by Planck. We show that this situation may also be alleviated by the inclusion of non-minimal terms in the Kahler potential. In these non-minimal hybrid inflation models, r may be as large as O(0.01)—tantalizingly close to the expected sensitivity limit of Planck—while simultaneously producing favorable ns values. Precise measurement of r can yield important and exciting information about both the energy scale of inflation and the amplitude of primordial gravity waves. In addition to refining the original model of supersymmetric hybrid inflation, we perform a similar analysis on the shifted hybrid model, which yields similar results while ensuring that any problematic topological defects are inflated away. We also examine radiative corrections to non-supersymmetric hybrid inflation, showing that this may produce ns values in better agreement with the WMAP measurements. In summary, we show that hybrid inflation models remain in good keeping with experimental results, and give interesting predictions relevant to future observations. |
