Kahler Moduli Inflation Revisited

TL;DR

This work embeds inflation in the Kahler moduli sector of Type IIB flux compactifications within the Large Volume Scenario, incorporating alpha' corrections and an uplift term. It first revisits the single-field inflation picture and then performs a comprehensive numerical study of the full multi-field potential, demonstrating inflationary trajectories even when multiple moduli evolve. A key finding is the existence of a basin of attraction along a constant-volume direction, preserving viable inflation over a broad initial-condition region, and yielding a robust scalar spectral index $n_s\approx0.96$ for about $60$ e-folds with negligible tensor modes. The analysis also reveals how axion dynamics influence viability, with perturbations in $\theta_2$ allowed but $\theta_3$ perturbations potentially triggering decompactification, and it discusses gravitino-mass scales during and after inflation. These results reinforce the robustness of Kahler moduli inflation in LVS and clarify the conditions under which successful multi-field inflation can occur in string-inspired models.

Abstract

We perform a detailed numerical analysis of inflationary solutions in Kahler moduli of type IIB flux compactifications. We show that there are inflationary solutions even when all the fields play an important role in the overall shape of the scalar potential. Moreover, there exists a direction of attraction for the inflationary trajectories that correspond to the constant volume direction. This basin of attraction enables the system to have an island of stability in the set of initial conditions. We provide explicit examples of these trajectories, compute the corresponding tilt of the density perturbations power spectrum and show that they provide a robust prediction of n_s approximately 0.96 for 60 e-folds of inflation.

Figures (9)

• Figure 1: Evolution of the $\tau_2$ field in the last few e-folds in Example 1.
• Figure 2: Evolution of the different moduli fields in the last few e-folds in Example 2. a) Evolution of the field $\tau_1$. b) Evolution of the field $\tau_3$.
• Figure 3: a) Evolution of the moduli field $\tau_2$ (the inflaton) in the last few e-folds in Example 2. b) Amplitude of the density perturbations in the 10 observationally relevant e-foldings..
• Figure 4: Evolution of the different moduli fields in the last few e-folds in Example 3. a) Evolution of the field $\tau_1$. b) Evolution of the field $\tau_2$.
• Figure 5: Evolution of the different moduli fields in the last few e-folds in Example 3. a) Evolution of the field $\tau_3$. b) Evolution of the field ${\cal{V}}$.