Mees de Roo

IIB supergravity revisited

We show in the SU(1,1)-covariant formulation that IIB supergravity allows the introduction of a doublet and a quadruplet of ten-form potentials. The Ramond-Ramond ten-form potential which is associated with the SO(32) type-I superstring is in the quadruplet. Our results are consistent with a recently proposed E11 symmetry underlying string theory. For the readers convenience we present the full supersymmetry and gauge transformations of all fields both in the manifestly SU(1,1) covariant Einstein frame and in the real U(1) gauge fixed string frame.

Newtonian gravity and the Bargmann algebra

We show how the Newton-Cartan formulation of Newtonian gravity can be obtained from gauging the Bargmann algebra, i.e., the centrally extended Galilean algebra. In this gauging procedure several curvature constraints are imposed. These convert the spatial (time) translational symmetries of the algebra into spatial (time) general coordinate transformations, and make the spin connection gauge fields dependent. In addition we require two independent Vielbein postulates for the temporal and spatial directions. In the final step we impose an additional curvature constraint to establish the connection with (on-shell) Newton-Cartan theory. We discuss a few extensions of our work that are relevant in the context of the AdS-CFT correspondence.

Multiple Membranes from Gauged Supergravity

Starting from gauged N = 8 supergravity in three dimensions we construct actions for multiple membranes by taking the limit to global supersymmetry for different choices of the embedding tensor. This provides a general framework that reproduces many recent results on multiple membrane actions as well as generalisations thereof. As examples we discuss conformal (non-conformal) gaugings leading to multiple M2-branes (D2-branes) and massive deformations of these systems.

The super D9-brane and its truncations

Abstract We consider two inequivalent truncations of the super D9-brane: the “Heterotic” and the “Type I” truncation. Both of them lead to an N = 1 non-linear supersymmetrization of the D = 10 cosmological constant. The propagating degrees of freedom in the Heterotic and Type I truncation are given by the components of a D = 10 vector multiplet and a single Majorana-Weyl spinor, respectively. As a by-product we find that, after the Type I truncation, the Ramond-Ramond super ten-form provides an interesting reformulation of the Volkov-Akulov action. These results can be extended to all dimensions in which space-time filling D-branes exist, i.e. D = 3, 4, 6 and 10.

De Sitter solutions in N = 4 matter coupled supergravity

We investigate the scalar potential of gauged N = 4 supergravity with matter. The extremum in the SU(1, 1)/U(1) scalars is obtained for an arbitrary number of matter multiplets. The constraints on the matter scalars are solved in terms of an explicit parametrisation of an SO(6, 6 + n) element. For the case of six matter multiplets we discuss both compact and noncompact gauge groups. In an example involving noncompact groups and four scalars we find a potential with an absolute minimum and a positive cosmological constant.

SL(2, R)-invariant IIB brane actions

We give a universal SL(2,)-invariant expression for all IIB p-brane actions with p = −1,1,3,5,7,9. The Wess-Zumino terms in the brane actions are determined by requiring (i) target space gauge invariance and (ii) the presence of a single Born-Infeld vector. We find that for p = 7 (p = 9) brane actions with these properties only exist for orbits that contain the standard D7-brane (D9-brane). We comment about the actions for the other orbits.

The eleven-dimensional five-brane

We consider the action, in arbitrary curved background, of the eleven-dimensional five-brane to second order in the curvature of the worldvolume tensor field. We show that this action gives upon double dimensional reduction the action of the Dirichlet four-brane up to the same order. We use this result as a starting point to discuss the structure of the action including terms of higher order in the worldvolume curvature.

'Stringy' Newton-Cartan Gravity

We construct a ‘stringy’ version of Newton–Cartan gravity in which the concept of a Galilean observer plays a central role. We present both the geodesic equations of motion for a fundamental string and the bulk equations of motion in terms of a gravitational potential which is a symmetric tensor with respect to the longitudinal directions of the string. The extension to include a nonzero cosmological constant is given. We stress the symmetries and (partial) gaugings underlying our construction. Our results provide a convenient starting point to investigate applications of the AdS/CFT correspondence based on the non-relativistic ‘stringy’ Galilei algebra.

Dual gravity and matter

We consider the problem of finding a dual formulation of gravity in the presence of non-trivial matter couplings. In the absence of matter a dual graviton can be introduced only for linearised gravitational interactions. We show that the coupling of linearised gravity to matter poses obstructions to the usual construction and comment on possible resolutions of this difficulty.

Thermodynamics of Born-Infeld Black Holes

We discuss the horizon structure for Born-Infeld black holes in the context of Einstein-Born-Infeld gravity. We show that the entropy function formalism agrees with a direct calculation of the entropy. With the entropy function formalism we also obtain the entropy when an axion-dilaton system as well as gravitational derivative corrections are included.