We present a detailed systematics for comparing warped brane inflation with the observations, incorporating the effects of both moduli stabilization and ultraviolet bulk physics. We explicitly construct an example of the inflaton potential governing the motion of a mobile D3 brane in the entire warped deformed conifold. This allows us to precisely identify the corresponding scales of the cosmic microwave background. The effects due to bulk fluxes or localized sources are parametrized using gauge/string duality. We next perform some sample scannings to explore the parameter space of the complete potential, and first demonstrate that without the bulk effects there can be large degenerate sets of parameters with observationally consistent predictions. When the bulk perturbations are included, however, the observational predictions are generally spoiled. For them to remain consistent, the magnitudes of the additional bulk effects need to be highly suppressed.PACS numbers: 98.80.Cq, 11.25.Mj CONSTRUCTING A POTENTIAL FOR WARPED BRANE INFLATIONThe inflationary paradigm [1] addresses a number of fine tuning problems of the standard hot big bang cosmology, such as the horizon and the flatness problems. It also predicts a nearly scale invariant power spectrum of the curvature perturbation, which has been verified to high accuracies by the observation of the thermal fluctuations in the cosmic microwave background (CMB) and the large scale structure of the universe [2,3]. Numerous models of inflation based on effective field theory have been proposed, however, distinct predictions of a given model crucially depend on its ultraviolet completion. To construct a truly predictive inflationary model, it is clearly important to embed it into a consistent microscopic theory of quantum gravity such as string theory.During the past few years, our understanding of the various ingredients for obtaining string inflation has been significantly expanded, and many models with increasing sophistication and striking signatures have been proposed (For recent developments, see Ref.[4] and references therein). In the coming decade, beyond the ongoing Sloan Digital Sky Survey [2] and the Wilkinson Microwave Anisotropy Probe [3], vastly improved cosmological data will become available from the advanced CMB observations [5], the CMB polarization experiments [6], the dark energy surveys [7] as well as the map of large scale structure [8]. They will allow us to constrain the parameter spaces of these models, and possibly to even rule out some of them. It is therefore of timely interest to perform a thoroughly updated and complete case study in such a direction 1 . In this paper we shall focus on one of the most 1 What we mean by "complete" should become clear momentarily.developed string inflation models in the literature, usually referred to as "brane inflation".The original setup of brane inflation first introduced in Ref. [9] is to consider a pair of spacetime-filling D3-D3 branes, separated at some distance greater than the local string length...

We study the inflationary dynamics in a model of slow-roll inflation in warped throat. Inflation is realized by the motion of a D-brane along the radial direction of the throat, and at later stages instabilities develop in the angular directions. We closely investigate both the single field potential relevant for the slow-roll phase, and the full multi-field one including the angular modes which becomes important at later stages. We study the main features of the instability process, discussing its possible consequences and identifying the vacua towards which the angular modes are driven.