Resonant non-Gaussianity

          @misc{ pirsa_PIRSA:10030037,
            doi = {10.48660/10030037},
            url = {https://pirsa.org/10030037},
            author = {Pajer, Enrico},
            keywords = {Quantum Fields and Strings},
            language = {en},
            title = {Resonant non-Gaussianity},
            publisher = {Perimeter Institute},
            year = {2010},
            month = {mar},
            note = {PIRSA:10030037 see, \url{https://pirsa.org}}
          }
          

Abstract

Two of the most exciting observables in the cosmic microwave background (CMB) radiation, which could deeply impact our picture of the early universe, are non-Gaussianity and tensor modes. A potential detection of tensor modes can be explained in terms of a model of large field inflation. Theoretical considerations suggest that a symmetry should be invoked in order to protect the flatness of the inflaton potential and hence an axion enjoying a shift symmetry is a natural candidate. As main example, I will present a model of inflation in string theory based on axion monodromy. Non-perturbative effects typically correct the axion potential leading to small sinusoidal modulations on top of an otherwise flat slow roll potential. It can be shown analytically that a resonance between the oscillations of the background and the oscillations of the curvature fluctuations is responsible for the production of an observably large non-Gaussian signal. An explicit expression for the shape of this resonant non-Gaussianity will be presented. There is essentially no overlap between this shape and the local, equilateral, and orthogonal shapes, and in fact resonant non-Gaussianity is not captured by the simplest version of the effective field theory of inflation. Hopefully the analytic expression for resonant non-Gaussianity will be useful to further observationally constrain this class of models.