Abstract:

Both WMAP and PLANCK have hinted at a slight suppression of power in the CMB temperature spectrum at large angular scales. Yet this power loss is usually unaccounted for by models that are claimed to provide a best fit to the data at first order, such as the Starobinsky f(R) model. In a first step, we demonstrate how to obtain a viable observational signature in f(R) theory by explicitly constructing higher order terms to the Starobinsky model. These higher order terms realise a shift symmetry breaking of the inflaton at large fields. In a second step, we describe a new inflationary scenario deriving from higher derivative corrections in String theory giving rise to a similar observational fingerprint.