Low scale inflation and the curvaton mechanism.pdfVIP

a r X i v : h e p - p h / 0 4 1 1 1 1 9 v 3 9 M a r 2 0 0 5 Low scale inflation and the curvaton mechanism Konstantinos Dimopoulos,1, ? David H. Lyth,1, ? and Yeinzon Rodr??guez1, 2, ? 1Department of Physics, Lancaster University, Lancaster LA1 4YB, UK 2Centro de Investigaciones, Universidad Antonio Narin?o, Cll 58A # 37-94, Bogota? D.C., Colombia (Dated: February 7, 2008) The primordial curvature perturbation may be due to a ‘curvaton’ field, which dominates (or almost dominates) the energy density before it decays. In the simplest version of the curvaton model the scale of inflation has to be quite high corresponding to a Hubble parameter H 107 GeV. We here explore two modifications of the curvaton model which can instead allow inflation at a low scale. (i) The curvaton is a Pseudo Nambu-Goldstone Boson (PNGB), with a symmetry-breaking phase transition during inflation. (ii) The curvaton mass increases suddenly at some moment after the end of inflation but before the onset of the curvaton oscillations. Both proposals can work but not in a completely natural way. Also, the lower bound on the scale of inflation depends somewhat on the details of the framework used. Nevertheless, we show that inflation with H as low as 1 TeV or lower is possible to attain. PACS numbers: 98.80.Cq I. INTRODUCTION The primordial curvature perturbation is generated presumably from the perturbation of some scalar field, which in turn is generated from the vacuum fluctuation during inflation. The scalar field responsible for the pri- mordial curvature perturbation is traditionally supposed to be the inflaton field, i.e. the field responsible for the dynamics and, in particular, the end of inflation [1]. This ‘inflaton hypothesis’ is economical, but it is quite difficult to implement and, if many scalar fields exist, it presum- ably is not particularly likely. An alternative is that the curvature perturbation is generated by a ‘curvaton’ field, which dominates (or almost dominates) th