Towards multi-field D-brane inflation in a warped throat

Abstract

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.

Inflation and String Theory

“…15 We will start with the simplified single-field treatment [218,637] in which the angular degrees of freedom are integrated out using an adiabatic approximation. This is not always consistent, as the angular fields can have masses that are smaller than the inflationary Hubble scale, but serves to develop intuition for the more complex multi-field dynamics studied in [240,255,533,535,673,674]. …”

Spinflation with angular potentials

“…Here, the internal metric is a strongly warped and deformed throat, which interpolates between a regular R 3 × S 3 tip, to an R × T 1,1 cone in the UV. The metric is usually presented as:g 8) where ǫ is the deformation parameter of the conifold; it is a dimensionful parameter ([ǫ 2/3 ] = L), and sets a scale for the throat as we will see presently. The 'radial' coordinate, η, is chosen so that the function K is expressible explicitly in analytic form: 9) and the g i 's are forms representing the angular directions, given explicitly by [19].)…”

“…In recent years there has been significant progress within the 'KKLT' framework, [1], in which the older idea of brane inflation [2], is realised via the motion of a brane in internal, hidden, extra dimensions [3] (see also [4,5,6,7,8] and the reviews [9]). In these scenarios the inflaton potential (of the position of a probe D3-brane) is flattened by fine-tuned cancellation of correction terms from moduli stabilizing wrapped branes and bulk effects so that inflation can occur.…”

A statistical approach to multifield inflation: many-field perturbations beyond slow roll

“…12 indicates the cumulative probability that many-field contributions to the scalar power have a given size, as measured by ξ exact/two . Comparing to the upper curve, which corresponds to ξ exact/one ≡ |P exact /P one − 1|, we see that when multifield effects are large, the likelihood of many-field 20 In principle, one can envision a scenario in which P exact ≈ P one P two , so that two-field and manyfield effects are both present but cancel out in the exact power (see §4.3.4 for a discussion of this point). Correspondingly, some scenarios with ξ exact/one < 0.01 could involve significant many-field effects.…”