Michael Haack

Fluid dynamics of R-charged black holes

We construct electrically charged AdS5 black hole solutions whose charge, mass and boost-parameters vary slowly with the space-time coordinates. From the perspective of the dual theory, these are equivalent to hydrodynamic configurations with varying chemical potential, temperature and velocity fields. We compute the boundary theory transport coefficients associated with a derivative expansion of the energy momentum tensor and R-charge current up to second order. In particular, for the current we find a first order transport coefficient associated with the vorticity of the fluid.

Gaugino condensates and D-terms from D7-branes

We investigate, at the microscopic level, the compatibility between D-term potentials from world-volume fluxes on D7-branes and non-perturbative superpotentials arising from gaugino condensation on a different stack of D7-branes. This is motivated by attempts to construct metastable de Sitter vacua in type IIB string theory via D-term uplifts. We find a condition under which the Kahler modulus, T, of a Calabi-Yau 4-cycle gets charged under the anomalous U(1) on the branes with flux. If in addition this 4-cycle is wrapped by a stack of D7-branes on which gaugino condensation takes place, the question of U(1)-gauge invariance of the (T-dependent) non-perturbative superpotential arises. In this case an index theorem guarantees that strings, stretching between the two stacks, yield additional charged chiral fields which also appear in the superpotential from gaugino condensation. We check that the charges work out to make this superpotential gauge invariant, and we argue that the mechanism survives the inclusion of higher curvature corrections to the D7-brane action.

Jumping through loops: on soft terms from large volume compactifications

We subject the phenomenologically successful large volume scenario of hep-th/0502058 to a first consistency check in string theory. In particular, we consider whether the expansion of the string effective action is consistent in the presence of D-branes and O-planes. Due to the no-scale structure at tree-level, the scenario is surprisingly robust. We compute the modification of soft supersymmetry breaking terms, and find only subleading corrections. We also comment that for large-volume limits of toroidal orientifolds and fibered Calabi-Yau manifolds the corrections can be more important, and we discuss further checks that need to be performed.

M theory compactified on Calabi-Yau fourfolds with background flux

Abstract We perform the Kaluza–Klein reduction of M-theory on warped Calabi–Yau fourfolds with non-trivial four-form flux turned on. The resulting scalar- and superpotential is computed and compared with the superpotential obtained by Gukov, Vafa and Witten using different methods.

Nonlinear viscous hydrodynamics in various dimensions using AdS/CFT

We compute coefficients of two-derivative terms in the hydrodynamic energy momentum tensor of a viscous fluid which has an AdSD dual with 3 ≤ D ≤ 7. For the case of D = 3 we obtain an exact AdS3 black hole solution, valid to all orders in a derivative expansion, dual to a perfect fluid in 1+1 dimensions.

Glueballs vs. gluinoballs: Fluctuation spectra in non-AdS/non-CFT

Abstract Building on earlier results on holographic bulk dynamics in confining gauge theories, we compute the spin-0 and spin-2 spectra of the Maldacena–Nunez and Klebanov–Strassler theories, that have non-singular supergravity duals. We construct and apply a numerical recipe for computing mass spectra from certain determinants. In the Klebanov–Strassler case, the spectra of states containing the glueball and gluinoball are universal and quadratic in the supergravity approximation, i.e., their mass-squareds depend on consecutive number as m 2 ∼ n 2 for large n, with a universal proportionality constant. The hardwall approximation appears to work poorly when compared to the unique spectra we find in the full theory with a smooth cap-off in the infrared.

Massive type IIA theory on K3

In this paper we study K3 compactification of ten-dimensional massive type-IIA theory with all possible Ramond-Ramond background fluxes turned on. The resulting six-dimensional theory is a new massive (gauged) supergravity with an action that is manifestly invariant under an O(4,20)/O(4) × O(20) duality symmetry. We discover that this six-dimensional theory interpolates between vacua of ten-dimensional massive IIA supergravity and vacua of massless IIA supergravity with appropriate background fluxes turned on. This in turn suggests a new 11-dimensional interpretation for the massive type-IIA theory.

Duality in heterotic vacua with four supercharges

Abstract We study heterotic vacua with four supercharges in three and four space–time dimensions and their duals obtained as M/F-theory compactified on Calabi–Yau fourfolds. We focus on their respective moduli spaces and derive the Kahler potential for heterotic vacua obtained as circle compactifications of four-dimensional N =1 heterotic theories. The Kahler potential of the dual theory is computed by compactifying 11-dimensional supergravity on Calabi–Yau fourfolds. The duality between these theories is checked for K3-fibred fourfolds and an appropriate F-theory limit is discussed.

An orientifold with fluxes and branes via T-duality

String compactifications with non-Abelian gauge fields localized on D-branes, with background NSNS and RR 3-form fluxes, and with non-trivial warp factors, can naturally exist within T-dual versions of type I string theory. We develop a systematic procedure to construct the effective bosonic Lagrangian of type I T-dualized along a six-torus, including the coupling to gauge multiplets on D3-branes and the modifications due to 3-form fluxes. Looking for solutions to the ten-dimensional equations of motion, we find warped products of Minkowski space and Ricci-flat internal manifolds. Once the warp factor is neglected, the resulting no-scale scalar potential of the effective four-dimensional theory combines those known for 3-form fluxes and for internal Yang–Mills fields and stabilizes many of the moduli. We perform an explicit comparison of our expressions to those obtained from N=4 gauged supergravity and find agreement. We also comment on the possibility to include D9-branes with world-volume gauge fluxes in the background with 3-form fluxes.

Nernst branes in gauged supergravity

A bstractWe study static black brane solutions in the context of N = 2 U(1) gauged supergravity in four dimensions. Using the formalism of first-order flow equations, we construct novel extremal black brane solutions including examples of Nernst branes, i.e. extremal black brane solutions with vanishing entropy density. We also discuss a class of non-extremal generalizations which is captured by the first-order formalism.