Magnetic fluxes and moduli stabilization

Abstract

Stabilization of closed string moduli in toroidal orientifold compactifications of type IIB string theory are studied using constant internal magnetic fields on D-branes and 3-form fluxes that preserve N = 1 supersymmetry in four dimensions. Our analysis corrects and extends previous work by us, and indicates that charged scalar VEV's need to be turned on, in addition to the fluxes, in order to construct a consistent supersymmetric model. As an explicit example, we first show the stabilization of all Kähler class and complex structure moduli by turning on magnetic fluxes on different sets of D9-branes that wrap the internal space T 6 in a compactified type I string theory, when a charged scalar on one of these branes acquires a non-zero VEV. The latter can also be determined by adding extra magnetized branes, as we demonstrate in a subsequent example. In a different model with magnetized D7-branes, in a IIB orientifold on T 6 /Z 2 , we show the stabilization of all the closed string moduli, including the axion-dilaton at weak string coupling g s , by turning on appropriate closed string 3-form fluxes. * Ignatios.Antoniadis@cern.ch † kumar@iopb.res.in ‡ Tristan.Maillard@cpht.polytechnique.fr arXiv:hep-th

Perturbative moduli stabilisation in type IIB/F-theory framework

“…It has been suggested that magnetised branes along (1, 1)-cycles of the internal compactification space can be used to stabilise the Kähler moduli, as an alternative to non-pertubative effects, at a de Sitter vacuum through the induced D-terms [18,19,20]. The advantage of magnetic fluxes on D-branes, as opposed to non-perturbative effects and D3-contributions, is that these have an exact string description at weak coupling (i.e.…”

“…In most cases, dS vacua can only be obtained by 'uplifting' the vacuum energy in the presence of anti-D3 branes (D3-branes for short), which break though supersymmetry explicitly (KKLT scenario [4]). This situation can, in principle, be remedied if instead of D3-branes, D-term contributions are taken into account in the effective action [16,17,18,19,20,21,22], emerging from internal magnetic fluxes along the D7-branes world volume. String realisations improving the KKLT scenario are also possible within the so-called large volume scenario in Calabi-Yau compactifications [23,24].…”

From twists and shifts to L‐R asymmetric D‐branes

“…We hope we have convinced the audience, that twists and shifts produce (unoriented) models with few or no T's that can incorporate other mechanisms of moduli stabilization, e.g. open [37,[49][50][51][52] and closed string fluxes [21], (non) anomalous U (1)'s [53,54], instanton effects, ... . Explicit computations are feasible, though very systematic scans may be very time-consuming (thousands of characters, ...) [55].…”

Forbidden territories in the string landscape

“…First, we consider space-filling magnetized D9-branes, that is, D9-branes carrying constant magnetic fluxes on their world-volumes, wrapped on the orientifolded T 6 along with orientifold three-planes [8,12,14].…”

“…Such a scheme has been proposed with a real six-torus as the compactification manifold [14], albeit in conjunction with non-zero VEV of charged scalars. However, as mentioned above, the different kinds of RR charges of the configuration must add up to zero, for cancelation of tadpoles of all kinds.…”