The BICEP2 observation of a large tensor-to-scalar ratio, r = 0.20+0.07-0.05, implies that the inflaton phi in single-field inflation models must satisfy phi ~ 10MPl in order to produce sufficient inflation. This is a problem if interaction terms suppressed by the Planck scale impose a bound phi lesssim MPl. Here we consider whether it is possible to have successful sub-Planckian inflation in the case of two-field inflation. The trajectory in field space cannot be radial if the effective single-field inflaton is to satisfy the Lyth bound. By considering a complex field Φ, we show that a near circular but aperiodic modulation of a |Φ|4 potential can reproduce the results of phi2 chaotic inflation for ns and r while satisfying |Φ| lesssim 0.01 MPl throughout. More generally, for models based on a |Φ|4 potential, the simplest sub-Planckian models are equivalent to phi2 and phi4/3 chaotic inflation.
Journal of Cosmology and Astroparticle Physics
- Pub Date:
- September 2014
- High Energy Physics - Phenomenology;
- Astrophysics - Cosmology and Nongalactic Astrophysics;
- High Energy Physics - Theory
- 7 pages, 2 figures. Some additional references and discussion. Version published in JCAP