We show that inflation in type IIB string theory driven by the volume modulus can be realized in the context of the racetrack-based Kallosh-Linde model ( KL ) of moduli stabilization .
Inflation here arises through the volume modulus slow-rolling down from a flat hill-top or inflection point of the scalar potential .
This situation can be quite generic in the landscape , where by uplifting one of the two adjacent minima one can turn the barrier either to a flat saddle point or to an inflection point supporting eternal inflation .
The resulting spectral index is tunable in the range of 0.93 \lesssim n _ { s } \lesssim 1 , and there is only negligible production of primordial gravitational waves r < 10 ^ { -6 } .
The flatness of the potential in this scenario requires fine-tuning , which may be justified taking into account the exponential reward by volume factors preferring the regions of the universe with the maximal amount of slow-roll inflation .
This consideration leads to a tentative prediction of the spectral index n _ { s } \approx 0.95 or n _ { s } \approx 0.93 depending on whether the potential has a symmetry \varphi \to - \varphi or not .