Unifying inflation and dark matter with the Peccei-Quinn field: Observable axions and observable tensors

A model of high scale inflation is presented where the radial part of the Peccei-Quinn (PQ) field with a non-minimal coupling to gravity plays the role of the inflaton, and the QCD axion is the dark matter. A quantum fluctuation of O(H/2π) in the axion field will result in a smaller angular fluctuation if the PQ field is sitting at a larger radius during inflation than in the vacuum. This changes the effective axion decay constant, fa, during inflation and dramatically reduces the production of isocurvature modes. This mechanism opens up a new window in parameter space where an axion decay constant in the range 1012GeV fa 1015GeV is compatible with observably large r. The exact range allowed for fa depends on the efficiency of reheating. This model also predicts a minimum possible value of r=10-3. The new window can be explored by a measurement of r possible with SPIDER and the proposed CASPEr experiment search for high fa axions.