Monodromy in the CMB: Gravity Waves and String Inflation

          @misc{ pirsa_PIRSA:08060140,
            doi = {10.48660/08060140},
            url = {https://pirsa.org/08060140},
            author = {Westphal, Alexander},
            keywords = {Quantum Fields and Strings, Particle Physics, Cosmology},
            language = {en},
            title = {Monodromy in the CMB: Gravity Waves and String Inflation},
            publisher = {Perimeter Institute},
            year = {2008},
            month = {jun},
            note = {PIRSA:08060140 see, \url{https://pirsa.org}}
          }
          

Abstract

We present a simple mechanism for obtaining large-field inflation, and hence a gravitational wave signature, from string theory compactified on twisted tori. For Nil manifolds, we obtain a leading inflationary potential proportional to phi^(2/3) in terms of the canonically normalized field phi, yielding predictions for the tilt of the power spectrum and the tensor-to-scalar ratio, $n_sapprox 0.98$ and $rapprox 0.04$ with 60 e-foldings of inflation; we note also the possibility of a variant with a candidate inflaton potential proportional to phi^(2/5). The basic mechanism involved in extending the field range -- monodromy in D-branes as they move in circles on the manifold -- arises in a more general class of compactifications, though our methods for controlling the corrections to the slow-roll parameters require additional symmetries.