We propose an alternative refined de Sitter conjecture. It is given by a natural condition on a combination of the first and second derivatives of the scalar potential. We derive our conjecture in the same weak coupling, semi‐classical regime where the previous refined de Sitter conjecture was derived, using the same tools together with a few more assumptions that we discuss. We further test and constrain free parameters in our conjecture using data points of a classical type IIA supergravity setup. Interestingly, our conjecture easily accommodates slow‐roll single field inflation with a concave potential, favored by observations. The standard quintessence potential is in tension with our new conjecture, and we thus propose a different type of quintessence model.

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.

An anti-D3-brane plays a crucial role in the construction of semirealistic cosmological models in string theory. Part of its action provides an uplift term that has been used to lift anti-de Sitter solutions to phenomenologically viable de Sitter vacua in the Kachru-Kallosh-Linde-Trivedi and large volume scenario (LVS) setups. In the last few years it has been shown that this uplift breaks supersymmetry spontaneously and can be described in the four-dimensional N ¼ 1 supergravity language by using constrained supermultiplets. Here we derive the complete four-dimensional N ¼ 1 supergravity action for an anti-D3-brane coupled to all closed-string background fields. In particular, we include the vector field, the scalar fields, and all fermions that live on the anti-D3-brane.

We discuss the properties of massive type IIA flux compactifications. In particular, we investigate in which case one can obtain dS vacua at large volume and small coupling. We support a general discussion of scaling symmetries with the analysis of a concrete example. We find that the large volume and weak coupling limit requires a large number of O6-planes. Since these are bound for any given compactification space one cannot get arbitrarily good control over α and string loop corrections. arXiv:1811.07880v2 [hep-th]

A simple, KKLT-like construction of de Sitter vacua in type IIA string theory is presented in an STU model with guidance from string theory U-duality and with an uplifting anti-D6-brane. In four dimensions the model is reduced to N = 1 supergravity with three chiral multiplets, namely S, T and U , as well as one nilpotent multiplet representing the anti-D6-brane.