On Brane Inflation With Volume Stabilization

TL;DR

The paper addresses the challenge of achieving inflation in string theory while stabilizing the compactification volume. It proposes the inflaton trench, a shift-symmetry-protected flat direction for the brane-distance modulus that arises in near-BPS brane configurations and persists under volume stabilization. By combining KKLT-style volume stabilization with D-term uplifting and a carefully chosen superpotential $W(\rho,S)=W_{KKLT}(\rho)\,e^{-{S^2\over2}}$, the authors obtain an AdS trench where the inflaton remains flat ($m^2_{\rm infl}\ll H^2$) and a dS uplift that preserves this structure, with loop corrections enabling slow-roll. The framework yields a concrete path for stringy brane inflation with stabilized volume and suggests broader implications for the string landscape and cosmological acceleration.

Abstract

The distance between BPS branes in string theory corresponds to a flat direction in the effective potential. Small deviations from supersymmetry may lead to a small uplifting of this flat direction and to brane inflation. However, this scenario can work only if the BPS properties of the branes and the corresponding flatness of the inflaton potential are preserved in the theories with the stable volume compactification. We present an ``inflaton trench'' mechanism that keeps the inflaton potential flat due to shift symmetry, which is related to near BPS symmetry in our model.

Figures (2)

• Figure 1: AdS trench at the point in the moduli space where $\alpha=0$ and $\beta=0$ which is a saddle point in these two variables. The exact supersymmetric trench corresponds to the minimum of the potential in the $\sigma$-direction and shows the neutral equilibrium in the $s$-direction.
• Figure 2: dS trench at the minimum of $\alpha=0$ and $\beta=1/2$ in which the volume $\sigma$ is stabilized close to the critical value of the AdS stage. There is no dependence of $V$ on the inflaton $s$.