New Vacua for Type II String Theory

TL;DR

The paper demonstrates that Lorentz-invariant RR background fluxes in IIA compactifications impart magnetic and electric charges to the dilaton multiplet, generating a moduli potential ${\cal V}$ with minima at zero coupling or at conifold points. A key finding is the quantization of the dilaton’s magnetic charge $\nu_0$, fixed by 8-brane charge $\mu_8$ and recoverable via a 0-brane/string setup, establishing discrete flux units. The large-radius potential scales as ${\cal V} \sim \nu_0^2 e^{4\phi+3D}$ (magnetic) or ${\cal V} \sim \nu_6^2 e^{4\phi-3D}$ (electric), consistent with 10D reductions, while near conifold points the interplay with light BPS black holes creates flat directions and a black-hole condensate of order $g_s$. These new vacua are interpreted as compactifications on generalized Calabi–Yau spaces with $c_1=0$ but non‑Kähler, offering avenues for moduli stabilization, confinement phenomena, and potential heterotic dual interpretations. The work thereby identifies novel, controlled non-Kähler backgrounds in type II string theory and outlines extensions to $N=1$ or higher settings with RR/NS-NS charge mixtures.

Abstract

Lorentz-invariant expectation values for antisymmetric tensor field strengths in Calabi-Yau compactification of IIA string theory are considered. These are found to impart magnetic and/or electric charges to the dilaton hypermultiplet. This results in a potential which can have supersymmetric minima at zero coupling or at conifold points in the moduli space. The latter occurs whenever the dilaton charge is aligned with that of the light black hole at the conifold. It is shown that there is a flat direction extending from the conifold along which there is a black hole condensate whose strength is of order the string coupling $g_s$. It is speculated that these new vacua correspond to string compactification on generalized Calabi-Yau spaces which have $c_1=0$ but are not Kahler.