N=3 Warped Compactifications

We study little string theory (LST) compactified on $\mathbf{T}^2$, partially breaking supersymmetry by a discrete T-duality twist acting on both the K\"ahler and the complex structure of the torus. This setup gives raise to 4d $\mathcal{N}=3$ models and it can be performed in both the type IIA and type IIB LSTs. We comment on the relation with other constructions proposed in the literature.

We describe a new class of supersymmetric string compactifications to 4d Minkowski space. These solutions involve type II strings propagating on (orientifolds of) non Calabi-Yau spaces in the presence of background NS and RR fluxes. The simplest examples have descriptions as cosets, generalizing the three-dimensional nilmanifold. They can also be thought of as twisted tori. We derive a formula for the (super)potential governing the light fields, which is generated by the flux...

I review type IIB string compactifications in which the three-form field strengths satisfy a self-duality condition on the internal manifold. I begin with an overview of the models, giving preliminary formulae and several points of view from which they can be understood. Then I describe windows into the small radius behavior of the compactifications, which is more complicated than compactifications without fluxes. I discuss details of the flux-generated potential and nonpertu...

We study novel type IIB compactifications on the T^6/Z_2 orientifold. This geometry arises in the T-dual description of Type I theory on T^6, and one normally introduces 16 space-filling D3-branes to cancel the RR tadpoles. Here, we cancel the RR tadpoles either partially or fully by turning on three-form flux in the compact geometry. The resulting (super)potential for moduli is calculable. We demonstrate that one can find many examples of N=1 supersymmetric vacua with greatl...

We consider non-perturbative six dimensional N=1 space-time supersymmetric orientifolds of Type IIB on K3 with non-trivial NS-NS B-flux. All of these models are non-perturbative in both orientifold and heterotic pictures. Thus, some states in such compactifications arise in ``twisted'' open string sectors which lack world-sheet description in terms of D-branes. We also discuss their dual F-theory compactifications on certain Voisin-Borcea orbifolds. In particular, the explici...

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 c...

We present a pedagogical overview of flux compactifications in string theory, from the basic ideas to the most recent developments. We concentrate on closed string fluxes in type II theories. We start by reviewing the supersymmetric flux configurations with maximally symmetric four-dimensional spaces. We then discuss the no-go theorems (and their evasion) for compactifications with fluxes. We analyze the resulting four-dimensional effective theories, as well as some of its pe...

We illustrate the correspondence between the N=1 superstring compactifications with fluxes, the N=4 gauged supergravities and the superpotential and K\"ahler potential of the effective N=1 supergravity in four dimensions. In particular we derive, in the presence of general fluxes, the effective N=1 supergravity theory associated to the type IIA orientifolds with D6 branes, compactified on $T^6/(Z_2 \times Z_2)$. We construct explicit examples with different features: in parti...

At the leading order, M-theory admits minimal supersymmetric compactifications if the internal manifold has exceptional holonomy. The inclusion of non-vanishing fluxes in M-theory and string theory compactifications induce a superpotential in the lower dimensional theory, which depends on the fluxes. In this work, we verify the conjectured form of this superpotential in the case of warped M-theory compactifications on Spin(7) holonomy manifolds. We calculate the most general ...

We consider D-branes and orientifold planes embedded in non-compact (orbifolded) space-time. We point out that even in the non-compact cases we can turn on non-zero (quantized) NS-NS antisymmetric B-field. In particular, we study the effect of the B-field on four dimensional large N gauge theories from orientifolds. Thus, in theories with both D3- and D7-branes, the effect of the B-field is non-trivial: the number of D7-branes (of each species) is reduced from 8 (which is the...