Non-geometric fluxes as supergravity backgrounds

We consider examples of D=4 string theory vacua which, although globally non-geometric, admit a local description in terms of D=10 supergravity backgrounds. We analyze such backgrounds and find that the supersymmetry spinors vary non-trivially along the internal manifold, reproducing the interpolating supergravity solutions found by Frey and Grana. Finally, we propose a simple, local expression for non-geometric fluxes in terms of the internal spinors of the compactification.Comment: 5 pages. Further typos correcte

The Algebra of Diffeomorphisms from the World Sheet

The quantum theory of a massless spin two particle is strongly constrained by diffeomorphism invariance, which is in turn implied by unitarity. We explicitly exhibit the space-time diffeomorphism algebra of string theory, realizing it in terms of world sheet vertex operators. Viewing diffeomorphisms as field redefinitions in the two-dimensional conformal field theory renders the calculation of their algebra straightforward. Next, we generalize the analysis to combinations of space-time anti-symmetric tensor gauge transformations and diffeomorphisms. We also point out a left-right split of the algebra combined with a twist that reproduces the C-bracket of double field theory. We further compare our derivation to an analysis in terms of marginal deformations as well as vertex operator algebras.Comment: 16 page

Asymptotic symmetry groups and operator algebras

We associate vertex operators to space-time diffeomorphisms in flat space string theory, and compute their algebra, which is a diffeomorphism algebra with higher derivative corrections. As an application, we realize the asymptotic symmetry group BMS3 of three-dimensional flat space in terms of vertex operators on the string worldsheet. This provides an embedding of the BMS3 algebra in a consistent theory of quantum gravity. Higher derivative corrections vanish asymptotically. An appendix is dedicated to alpha prime corrected algebras in conformal field theory and string theory.Comment: 25 page

Correlation Functions and Hidden Conformal Symmetry of Kerr Black Holes

Extremal scalar three-point correlators in the near-NHEK geometry of Kerr black holes have recently been shown to agree with the result expected from a holographically dual non-chiral two-dimensional conformal field theory. In this paper we extend this calculation to extremal three-point functions of scalars in a general Kerr black hole which need not obey the extremality condition $M=\sqrt{J}$. It was recently argued that for low frequency scalars in the Kerr geometry there is a dual conformal field theory description which determines the interactions in this regime. Our results support this conjecture. Furthermore, we formulate a recipe for calculating finite-temperature retarded three-point correlation functions which is applicable to a large class of (even non-extremal) correlators, and discuss the vanishing of the extremal couplings.Comment: 16 page

Moduli Stabilization in type IIB Orientifolds

Diese Arbeit beschäftigt sich mit der Stabilisierung der Modulifelder bei den Kompaktifizierungen der Typ IIB String Theorie auf Orientifolds. Ein konkretes Verfahren für die Konstruktion von Lösungen, bei denen alle Modulifelder fixiert sind, bietet das KKLT-Szenario. Wir untersuchen, auf welche Modelle das Szenario sich anwenden lässt, wenn man auf Näherungen der originalen KKLT-Arbeit verzichtet. Wir finden, dass bei einer Reihe von Modellen, nämlich solchen ohne Komplexe-Struktur-Moduli, die Konstruktion der konsistenten Lösungen im Rahmen des KKLT-Szenarios nicht möglich ist. Die nichtperturbativen Effekte, wie D3-Instantonen und Gauginokondensate, sind ein weiterer Bestandteil des KKLT-Szenarios. Sie führen zur Stabilisierung der Kählermoduli. Wir geben Kriterien an für das Erzeugen des Superpotentials infolge der D3-Instantonen bei einer Calabi-Yau-Mannigfaltigkeit in Anwesenheit der Flüsse. Weiterhin zeigen wir, dass obwohl die Anwesenheit des nichtperturbativen Superpotentials in den Bewegungsgleichungen mit dem Einschalten aller ISD- und IASD-Flüsse korreliert, das Entscheidungkriterium für das Erzeugen des nichtperturbativen Superpotentials nur von den Flüssen vom Typ (2,1) abhängt. Anschließend diskutieren wir zwei Modelle, bei denen wir alle Modulifelder stabilisieren. Dabei handelt es sich um Calabi-Yau-Orientifolds, die man durch eine Blow-Up-Prozedur aus den Z_6 und Z_2 x Z_4 Orientifolds erhalten hat

Liouville theory beyond the cosmological horizon

The dS/CFT correspondence postulates the existence of a Euclidean CFT dual to a suitable gravity theory with Dirichlet boundary conditions asymptotic to de Sitter spacetime. A semi-classical model of such a correspondence consists of Einstein gravity with positive cosmological constant and without matter which is dual to Euclidean Liouville theory defined at the future conformal boundary. Here we show that Euclidean Liouville theory is also dual to Einstein gravity with Dirichlet boundary conditions on a fixed timelike slice in the static patch. Intriguingly, the spacetime interpretation of Euclidean Liouville time is the physical time of the static observer. As a prerequisite of this correspondence, we show that the asymptotic symmetry algebra which consists of two copies of the Virasoro algebra extends everywhere into the bulk.Comment: 19 page

Extremal three-point correlators in Kerr/CFT

We compute three-point correlation functions in the near-extremal, near-horizon region of a Kerr black hole, and compare to the corresponding finite-temperature conformal field theory correlators. For simplicity, we focus on scalar fields dual to operators ${\cal O}_h$ whose conformal dimensions obey $h_3=h_1+h_2$, which we name \emph{extremal} in analogy with the classic $AdS_5 \times S^5$ three-point function in the literature. For such extremal correlators we find perfect agreement with the conformal field theory side, provided that the coupling of the cubic interaction contains a vanishing prefactor $\propto h_3-h_1-h_2$. In fact, the bulk three-point function integral for such extremal correlators diverges as $1/(h_3-h_1-h_2)$. This behavior is analogous to what was found in the context of extremal AdS/CFT three-point correlators. As in AdS/CFT our correlation function can nevertheless be computed via analytic continuation from the non-extremal case.Comment: 22 pages; v2: references added, typos correcte

Boundary Terms, Spinors and Kerr/CFT

Similarly as in AdS/CFT, the requirement that the action for spinors be stationary for solutions to the Dirac equation with fixed boundary conditions determines the form of the boundary term that needs to be added to the standard Dirac action in Kerr/CFT. We determine this boundary term and make use of it to calculate the two-point function for spinor fields in Kerr/CFT. This two-point function agrees with the correlator of a two dimensional relativistic conformal field theory.Comment: 15 page

Backreacted T-folds and non-geometric regions in configuration space

We provide the backreaction of the T-fold doubly T-dual to a background with NSNS three-form flux on a three-torus. We extend the backreacted T-fold to include cases with a flux localized in one out of three directions. We analyze the resulting monodromy domain walls and vortices. In these backgrounds, we give an analysis of the action of T-duality on observables like charges and Wilson surfaces. We analyze arguments for the existence of regions in the configuration space of second quantized string theory that cannot be reduced to geometry. Finally, by allowing for space-dependent moduli, we find a supergravity solution which is a T-fold with hyperbolic monodromies.Comment: 25 pages, 4 figures; v2: minor changes, reference adde

Fermion Zero Modes in the Presence of Fluxes and a Non-perturbative Superpotential

We study the effect of background fluxes of general Hodge type on the supersymmetry conditions and on the fermionic zero modes on the world-volume of a Euclidean M5/D3-brane in M-theory/type IIB string theory. Using the naive susy variation of the modulino fields to determine the number of zero modes in the presence of a flux of general Hodge type, an inconsistency appears. This inconsistency is resolved by a modification of the supersymmetry variation of the modulinos, which captures the back-reaction of the non-perturbative effects on the background flux and the geometry.Comment: 21 pages, revised version contains a new appendix on dimensional reduction of spinors and some changes in the spinor equation