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such that the action in the Einstein frame reads 

In order to keep canonical kinetic terms once the metric is redefined, the potential U for the new field χ now reads 

At low energies, that is for small VEVs, Ω 2 ≃ 1, h ≃ χ and the two frames are indistin- guishable. At high energies, h ∝ exp χ , and the potential tends to 

<img src='content_image/349210.jpg'>

<img src='content_image/349219.jpg'>

<img src='content_image/349218.jpg'>

Once the potential is known at high energies, it is straightforward to compute the CMB predictions for the model. From Eq. (215), the slow-roll parameters read [86] 

<img src='content_image/349217.jpg'>

which requires inflation to take place in the range h ∈ [1 . 07 − 9 . 4] M$_{P}$$_{/}$√$_{ξ}$$_{.}$ A correct normalization to the COBE data imposes ξ ≃ 5 × 10 4 √$_{λ}$$_{, and the model predicts, at the}$ classical level [86, 589], 

<img src='content_image/349216.jpg'>

which is in agreement with the most recent WMAP data. 

The main challenge to this model is to evaluate the quantum corrections to the infla- tionary potential at high energyto evaluate if the flatness of the inflationary potential can be destabilized by them. Both the quantum gravity corrections and the quantum correc- tions due to SM particles can be evaluated, though the full quantum gravity corrections cannot be rigorously computed. It has been argued in Ref. [86] that the model is safe since 

<img src='content_image/349215.jpg'>

The leading log method [86] as well as renormalization group (RG) methods have been implemented [588, 589] in both frames to compute corrections to V , and ξ . The corrections from SM particles to V using RG improved calculation with 2-loop beta-function are also found in Ref. [589] to be very small and do not spoil the model (see Fig. 3). However, they 

