Type IIA Flux Compactifications Research Articles

New families of scale separated vacua

Massive type IIA flux compactifications of the form AdS4 × X6, where X6 admits a Calabi-Yau metric and O6-planes wrapping three-cycles, display families of vacua with parametric scale separation between the compactification scale and the AdS4 radius, generated by an overall rescaling of internal four-form fluxes. For toroidal orbifolds one can perform two T-dualities and map this background to an orientifold of massless type IIA compactified on an SU(3)-structure manifold with fluxes. Via a 4d EFT analysis, we generalise this last construction and embed it into new branches of supersymmetric and non-supersymmetric vacua with similar features. We apply our results to propose new infinite families of vacua based on elliptic fibrations with metric fluxes. Parametric scale separation is achieved by an asymmetric flux rescaling which, however, in general is not a simple symmetry of the 4d equations of motion. At this level of approximation the vacua are stable but, unlike in the Calabi-Yau case, they display a non-universal mass spectrum of light fields.

BIonic membranes and AdS instabilities

We study 4d membranes in type IIA flux compactifications of the form AdS4× X6, where X6 admits a Calabi-Yau metric. These models feature scale separation and D6-branes/O6-planes on three-cycles of X6. When the latter are treated as localised sources, explicit solutions to the 10d equations of motion and Bianchi identities are known in 4d mathcal{N} = 1 settings, valid at first order in an expansion parameter related to the AdS4 cosmological constant. We extend such solutions to a family of perturbatively stable mathcal{N} = 0 vacua, and analyse their non-perturbative stability by looking at 4d membranes. Up to the accuracy of the solution, we find that either D4-branes or anti-D4-branes on holomorphic curves feel no force in both mathcal{N} = 1 and mathcal{N} = 0 AdS4. Differently, D8-branes wrapping X6 and with D6-branes ending on them can be superextremal 4d membranes attracted towards the mathcal{N} = 0 AdS4 boundary. The sources of imbalance are the curvature of X6 and the D8/D6 BIon profile, with both comparable terms as can be checked for X6 a (blown-up) toroidal orbifold. We then show that simple mathcal{N} = 0 vacua with space-time filling D6-branes are unstable against bubble nucleation, decaying to mathcal{N} = 0 vacua with less D6-branes and larger Romans mass.

Sharpening the boundaries between flux landscape and swampland by tadpole charge

We investigate the vacuum structure of four-dimensional effective theory arising from Type IIB flux compactifications on a mirror of the rigid Calabi-Yau threefold, corresponding to a T-dual of the DeWolfe-Giryavets-Kachru-Taylor model in Type IIA flux compactifications. By analyzing the vacuum structure of this interesting corner of string landscape, it turns out that there exist perturbatively unstable de Sitter (dS) vacua in addition to supersymmetric and non-supersymmetric anti-de Sitter vacua. On the other hand, the stable dS vacua appearing in the low-energy effective action violate the tadpole cancellation condition, indicating a strong correlation between the existence of dS vacua and the flux-induced D3-brane charge (tadpole charge). We also find analytically that the tadpole charge constrained by the tadpole cancellation condition emerges in the scalar potential in a nontrivial way. Thus, the tadpole charge would restrict the existence of stable dS vacua, and this fact underlies the statement of the dS conjecture. Furthermore, our analytical and numerical results exhibit that distributions of mathcal{O}(1) parameters in expressions of several swampland conjectures peak at specific values.

T -dualizing de Sitter no-go scenarios

In the context of realizing de Sitter vacua and the slow-roll inflation, several no-go conditions have been found in the framework of type IIA (generalized) flux compactifications. In this article, using our recently proposed $T$-dual dictionary [P. Shukla, A dictionary for the type II non-geometric flux compactifications, arXiv:1909.07391], we translate various such type IIA no-go conditions that subsequently lead to some interesting de Sitter no-go scenarios in the presence of (non)geometric fluxes on the dual type IIB side. We also present the relevance of using $K3/{\mathbb{T}}^{4}$-fibered Calabi Yau threefolds in order to facilitate one particular class of the de Sitter no-go conditions. This analysis helps in refining certain corners of the vast nongeometric flux landscape for the hunt of de Sitter vacua.

Scaling limits of dS vacua and the swampland

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.

Weakly coupled de Sitter vacua with fluxes and the swampland

It was recently argued that the swampland distance conjecture rules out dS vacua at parametrically large field distances. We point out that this conclusion can in principle be avoided in the presence of large fluxes that are not bounded by a tadpole cancellation condition. We then study this possibility in the concrete setting of classical type IIA flux compactifications with (anti-)O6-planes, (anti-)D6-branes and/or KK monopoles and show that, nonetheless, parametrically controlled dS vacua are strongly constrained. In particular, we find that such dS vacua are ruled out at parametrically large volume and/or parametrically small string coupling. We also find obstructions in the general case where the parametrically large field is an arbitrary field combination.

Large field inflation from D-branes

We propose new large field inflation scenarios built on the framework of F-term axion monodromy. Our setup is based on string compactifications where D-branes create potentials for closed string axions via F-terms. Because the source of the axion potential is different from the standard sources of moduli stabilization, it is possible to lower the inflaton mass as compared to other massive scalars. We discuss a particular class of models based on type IIA flux compactifications with D6-branes. In the small field regime they describe supergravity models of quadratic chaotic inflation with a stabilizer field. In the large field regime the inflaton potential displays a flattening effect due to Planck suppressed corrections, allowing us to easily fit the cosmological parameters of the model within current experimental bounds.

Black branes in flux compactifications

AbstractWe construct charged black branes in type IIA flux compactifications that are dual to (2 + 1)-dimensional field theories at finite density. The internal space is a general Calabi-Yau manifold with fluxes, with internal dimensions much smaller than the AdS radius. Gauge fields descend from the 3-form RR potential evaluated on harmonic forms of the Calabi-Yau, and Kaluza-Klein modes decouple. Black branes are described by a four-dimensional effective field theory that includes only a few light fields and is valid over a parametrically large range of scales. This effective theory determines the low energy dynamics, stability and thermodynamic properties. Tools from flux compactifications are also used to construct holographic CFTs with no relevant scalar operators, that can lead to symmetric phases of condensed matter systems stable to very low temperatures. The general formalism is illustrated with simple examples such as toroidal compactifications and manifolds with a single size modulus. We initiate the classification of holographic phases of matter described by flux compactifications, which include generalized Reissner-Nordstrom branes, nonsupersymmetric$ Ad{S_2}\times {{\mathbb{R}}^2} $and hyperscaling violating solutions.

M-theory and type IIA flux compactifications

We consider compactifications of M-theory and type IIA string theory to four dimensions. For Minkowski space-time, a supergravity no-go theorem forbids flux supported in the internal space. We show how to evade this no-go theorem by exhibiting new sources of brane charge: in string theory, the basic physical phenomenon is the generation of new brane charges from D-branes in transverse fluxes. In M-theory, there is a new source of M5-brane charge from novel higher derivative couplings that involve fluxes as well as curvatures. We present some explicit orientifold examples with both N=1 and N=2 space-time supersymmetry. Finally, we explain the status of massive type IIA flux compactifications.

Vacua analysis in extended supersymmetry compactifications

AbstractWe analyse geometric type IIA flux compactifications leading to 𝒩 = 4 gauged supergravities in four dimensions. The complete landscape of isotropic vacua is presented, which turns out to belong to a unique theory. The solutions admit an uplift to maximal supergravity due to the vanishing of the flux‐induced tadpoles for all the supersymmetry‐breaking branes. Such an uplift is sketched out and the full 𝒩 = 8 mass spectra are discussed. We find the interesting presence of a non‐supersymmetric and nevertheless stable minimum.

Type-IIA flux compactifications and 𝒩 = 4 gauged supergravities

We establish the precise correspondence between Type-IIA flux compactifications preserving an exact or spontaneously broken N=4 supersymmetry in four dimensions, and gaugings of their effective N=4 supergravities. We exhibit the explicit map between fluxes and Bianchi identities in the higher-dimensional theory and generalized structure constants and Jacobi identities in the reduced theory, also detailing the origin of gauge groups embedded at angles in the duality group. We present AdS4 solutions of the massive Type-IIA theory with spontaneous breaking to N=1, at small string coupling and large volume, and discuss their dual CFT3.

Type IIA Flux Compactifications

I review the current status of type IIA flux compactifications on SU(3)-structure manifolds including O6 planes to N=1, d=4 supergravity.

Fixing Moduli in Exact Type IIA Flux Vacua

Type IIA flux compactifications with O6-planes have been argued from a four dimensional effective theory point of view to admit stable, moduli free solutions. Here the ten dimensional description of such vacua is described in details and exact supersymmetric solutions are presented in the case when the O6-charge is smoothly distributed: the geometry is Calabi-Yau and the dilaton is constant. In the localized case, the solution is shown to be half-flat, with non-Calabi-Yau metric but still with constant dilaton. Finally, using the 10d description it is shown how all moduli are stabilized, reproducing precisely the results of de Wolfe et al . [O. DeWolfe, A. Giryavets, S. Kachru and W. Taylor, JHEP 0507, 066 (2005) [ arXiv:hep-th/0505160 ]]. The talk is based on [B.S. Acharya, F. Benini and R. Valandro, arXiv:hep-th/0607223 ].

Fixing moduli in exact type IIA flux vacua

Type IIA flux compactifications with O6-planes have been argued from a four dimensional effective theory point of view to admit stable, moduli free solutions. We discuss in detail the ten dimensional description of such vacua and present exact solutions in the case when the O6-charge is smoothly distributed. In the localised case, the solution is a half-flat, non-Calabi-Yau metric. Finally, using the ten dimensional description we show how all moduli are stabilised and reproduce precisely the results of de Wolfe et al.

D6-branes and torsion

The D6-brane spectrum of type IIA vacua based on twisted tori and RR background fluxes is analyzed. In particular, we compute the torsion factors of the (co)homology groups H_n and describe the effect that they have on D6-brane physics. For instance, the fact that H_3 contains Z_N subgroups explains why RR tadpole conditions are affected by geometric fluxes. In addition, the presence of torsional (co)homology shows why some D6-brane moduli are lifted, and it suggests how the D-brane discretum appears in type IIA flux compactifications. Finally, we give a clear, geometrical understanding of the Freed-Witten anomaly in the present type IIA setup, and discuss its consequences for the construction of semi-realistic flux vacua.