Degeneracies in inflationary signatures of UV physics

Inflation is a period of exponential expansion in the early universe. It should thus arise from and be described by some UV complete theory, which is unknown. Ideally, data taken today would allow us to say something about this UV physics, or at least differentiate between the many classes of inflationary models on the market. Nongaussianities in the CMB seemed a promising way to learn about the physics underlying inflation. However, not only do nongaussianities remain almost completely unconstrained by the Planck data, there is also huge degeneracy in the space of models and their predictions. In particular, the observables associated with noncanonical inflation, in which higher powers of the kinetic term of the inflation enter, can be shown to arise in canonical single field theories. This includes the characteristic equilateral-type nongaussian signal, for the current bounds.

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