de Sitter extrema and the swampland

TL;DR

The paper confronts the dS swampland conjecture by analyzing concrete classical string backgrounds: type II flux compactifications on SU(3) structure manifolds with fluxes, D-branes, and O-planes. It revisits known de Sitter critical points, constructs hundreds of new candidates, and subjects them to consistency checks such as flux quantization, tadpole cancellation, and the requirements of large volume and weak coupling. The analysis uncovers that many dS points rely on smeared sources and do not survive full 10d localization once quantization and tadpole constraints are imposed; even after invoking a universal rescaling to adjust tadpoles, the combination $(F_0)^2 \mathrm{vol}_6$ typically lies between $O(1)$ and $O(100)$, making large volume with integer $F_0$ challenging. These results indicate a potential tension with the bound $|\nabla V| \ge c\, V$ with $c=\mathcal{O}(1)$, motivating exploration of non-geometric fluxes, dual frames, or alternative vacua to robustly realize de Sitter physics in string theory.

Abstract

Recently it has been conjectured that string theory does not allow for dS vacua or dS extrema. To scrutinize such a conjecture, it is important to study concrete string theory compactifications and spell out their assumptions and potential shortcomings. We do so for one particular class of string compactifications, namely classical compactifications of type II string theory with fluxes, D-branes and O-planes on manifolds with SU(3) structure. In particular, we revisit previously found dS critical points, construct many new ones and check whether they invalidate the dS swampland conjecture.