Towards an explicit model of D-brane inflation

Abstract

We present a detailed analysis of an explicit model of warped D-brane inflation,incorporating the effects of moduli stabilization. We consider the potential for D3-branemotion in a warped conifold background that includes fluxes and holomorphicallyembedded D7-branes involved in moduli stabilization. Although the D7-branes significantlymodify the inflaton potential, they do not correct the quadratic term in the potential, andhence do not cause a uniform change in the slow roll parameter eta. Nevertheless,we present a simple example based on the Kuperstein embedding of D7-branes,z1 = constant, in which the potential can be fine-tuned to be sufficiently flat for inflation. To derive thisresult, it is essential to incorporate the fact that the compactification volume changesslightly as the D3-brane moves. We stress that the compactification geometry dictatescertain relationships among the parameters in the inflaton Lagrangian, and thesemicroscopic constraints impose severe restrictions on the space of possible models. We notethat the shape of the final inflaton potential differs from projections given in earlier studies:in configurations where inflation occurs, it does so near an inflection point. Finally,we comment on the difficulty of making precise cosmological predictions in thisscenario. This is the companion paper to Baumann et al (2007 Phys. Rev. Lett. 99141601).