Maximally supersymmetric solutions of D=4 N=2 gauged supergravity (2009)
Hristov, Kiril, Looyestijn, Hugo, Vandoren, Stefan
We determine and analyze maximally supersymmetric configurations in four-dimensional gauged N=2 supergravity, preserving eight supercharges. These models include arbitrary electric gaugings in the...
Large D-instanton effects in string theory (2009)
Pioline, Boris, Vandoren, Stefan
By reduction along the time direction, black holes in 4 dimensions yield instantons in 3 dimensions. Each of these instantons contributes individually at order $\exp(-|Q|/g_s)$ to certain protected...
D-instantons and twistors (2008)
Alexandrov, Sergei, Pioline, Boris, Saueressig, Frank, Vandoren, Stefan
Finding the exact, quantum corrected metric on the hypermultiplet moduli space in Type II string compactifications on Calabi-Yau threefolds is an outstanding open problem. We address this issue by...
Linear perturbations of quaternionic metrics - II. The quaternionic-Kahler case (2008)
Alexandrov, Sergei, Pioline, Boris, Saueressig, Frank, Vandoren, Stefan
We extend the twistor methods developed in our earlier work on linear deformations of hyperkahler manifolds [arXiv:0806.4620] to the case of quaternionic-Kahler manifolds. Via Swann's construction,...
Linear perturbations of Hyperkahler metrics (2008)
Alexandrov, Sergei, Pioline, Boris, Saueressig, Frank, Vandoren, Stefan
We study general linear perturbations of a class of 4d real-dimensional hyperkahler manifolds obtainable by the (generalized) Legendre transform method. Using twistor methods, we show that...
Vandoren, Stefan, Van Nieuwenhuizen, Peter
This is a self-contained set of lecture notes on instantons in (super) Yang-Mills theory in four dimensions and in quantum mechanics. First the basics are derived from scratch: the regular and...
On NS5-brane instantons and volume stabilization (2008)
Looyestijn, Hugo, Vandoren, Stefan
We study general aspects of NS5-brane instantons in relation to the stabilization of the volume modulus in Calabi-Yau compactifications of type II strings with fluxes, and their orientifold versions....
Membrane instantons from mirror symmetry (2007)
Robles-Llana, Daniel, Saueressig, Frank, Theis, Ulrich, Vandoren, Stefan
We use mirror symmetry to determine and sum up a class of membrane instanton corrections to the hypermultiplet moduli space metric arising in Calabi-Yau threefold compactifications of type IIA...
Twistors and Black Holes (2007)
Neitzke, Andrew, Pioline, Boris, Vandoren, Stefan
Motivated by black hole physics in N=2, D=4 supergravity, we study the geometry of quaternionic-Kahler manifolds M obtained by the c-map construction from projective special Kahler manifolds M_s....
Conifold singularities, resumming instantons and non-perturbative mirror symmetry (2007)
Saueressig, Frank, Vandoren, Stefan
We determine the instanton corrected hypermultiplet moduli space in type IIB compactifications near a Calabi-Yau conifold point where the size of a two-cycle shrinks to zero. We show that...
Orientifolding in N=2 Superspace (2007)
Robles-Llana, Daniel, Rocek, Martin, Saueressig, Frank, Theis, Ulrich, Vandoren, Stefan
We discuss orientifold projections on superspace effective actions for hypermultiplets. We present a simple and new mechanism that allows one to find the Kahler potential and complex structure for...
Twistors and Black Holes (2007)
Neitzke, Andrew, Pioline, Boris, Vandoren, Stefan
Motivated by black hole physics in N=2, D=4 supergravity, we study the geometry of quaternionic-Kahler manifolds M obtained by the c-map construction from projective special Kahler manifolds M_s....
Robles-Llana, Daniel, Rocek, Martin, Saueressig, Frank, Theis, Ulrich, Vandoren, Stefan
We find the D(-1) and D1-brane instanton contributions to the hypermultiplet moduli space of type IIB string compactifications on Calabi-Yau threefolds. These combine with known perturbative and...
The identification of conformal hypercomplex and quaternionic manifolds (2006)
We review the map between hypercomplex manifolds that admit a closed homothetic Killing vector (i.e. "conformal hypercomplex" manifolds) and quaternionic manifolds of one dimension less. This map is...
Supergravity description of spacetime instantons (2006)
De Vroome, Mathijs, Vandoren, Stefan
We present and discuss BPS instanton solutions that appear in type II string theory compactifications on Calabi-Yau threefolds. From an effective action point of view these arise as finite action...
Membrane and fivebrane instantons from quaternionic geometry (2006)
Alexandrov, Sergei, Saueressig, Frank, Vandoren, Stefan
We determine the one-instanton corrections to the universal hypermultiplet moduli space coming both from Euclidean membranes and NS-fivebranes wrapping the cycles of a (rigid) Calabi-Yau threefold....
Quaternion-Kahler spaces, hyperkahler cones, and the c-map (2006)
Rocek, Martin, Vafa, Cumrun, Vandoren, Stefan
Under the action of the c-map, special Kahler manifolds are mapped into a class of quaternion-Kahler spaces. We explicitly construct the corresponding Swann bundle or hyperkahler cone, and determine...
String loop corrected hypermultiplet moduli spaces (2006)
Robles-Llana, Daniel, Saueressig, Frank, Vandoren, Stefan
Using constraints from supersymmetry and string perturbation theory, we determine the string loop corrections to the hypermultiplet moduli space of type II strings compactified on a generic...
The Map Between Conformal Hypercomplex/Hyper-Kähler and Quaternionic(-Kähler) Geometry (2006)
Vandoren, Stefan, Gheerardyn, Jos, Wit, Tim De, Cucu, Sorin, Bergshoeff, Eric, Proeyen, Antoine Van
We review the general properties of target spaces of hypermultiplets, which are quaternionic-like manifolds, and discuss the relations between these manifolds and their symmetry generators. We...
Non-extremal D-instantons and the AdS/CFT correspondence (2006)
Riet, Thomas Van, Ploegh, André, Collinucci, Andrés, Bergshoeff, Eric, Vandoren, Stefan
We investigate non-extremal D-instantons in an asymptotically AdS5 × S5 background and the role they play in the AdS5/CFT4 correspondence. We find that the holographic dual operators of non-extremal...
Hypermultiplets and Topological Strings (2005)
Rocek, Martin, Vafa, Cumrun, Vandoren, Stefan
The c-map relates classical hypermultiplet moduli spaces in compactifications of type II strings on a Calabi-Yau threefold to vector multiplet moduli spaces via a further compactification on a...
The identification of conformal hypercomplex and quaternionic manifolds (2005)
Bergshoeff, Eric, Vandoren, Stefan, Van Proeyen, Antoine
We review the map between hypercomplex manifolds that admit a closed homothetic Killing vector (i.e. `conformal hypercomplex' manifolds) and quaternionic manifolds of 1 dimension less. This map is...
On de Sitter Vacua in Type IIA Orientifold Compactifications (2005)
Saueressig, Frank, Theis, Ulrich, Vandoren, Stefan
This letter discusses the orientifold projection of the quantum corrections to type IIA strings compactified on rigid Calabi-Yau threefolds. It is shown that N=2 membrane instanton effects give a...
Membrane Instantons and de Sitter Vacua (2005)
Davidse, Marijn, Saueressig, Frank, Theis, Ulrich, Vandoren, Stefan
We investigate membrane instanton effects in type IIA strings compactified on rigid Calabi-Yau manifolds. These effects contribute to the low-energy effective action of the universal hypermultiplet....
The map between conformal hypercomplex/hyper-Kaehler and quaternionic(-Kaehler) geometry (2004)
Bergshoeff, Eric, Cucu, Sorin, De Wit, Tim, Gheerardyn, Jos, Vandoren, Stefan, Van Proeyen, Antoine
We review the general properties of target spaces of hypermultiplets, which are quaternionic-like manifolds, and discuss the relations between these manifolds and their symmetry generators. We...
Fivebrane Instanton Corrections to the Universal Hypermultiplet (2004)
Davidse, Marijn, Theis, Ulrich, Vandoren, Stefan
We analyze the Neveu-Schwarz fivebrane instanton in type IIA string theory compactifications on rigid Calabi-Yau threefolds, in the low-energy supergravity approximation. It there appears as a finite...
N=2 supergravity in five dimensions revisited (2004)
Bergshoeff, Eric, Cucu, Sorin, De Wit, Tim, Gheerardyn, Jos, Vandoren, Stefan, Van Proeyen, Antoine
We construct matter-coupled N=2 supergravity in five dimensions, using the superconformal approach. For the matter sector we take an arbitrary number of vector-, tensor- and hyper-multiplets. By...
Quantum Corrections to the Universal Hypermultiplet and Superspace (2004)
Anguelova, Lilia, Rocek, Martin, Vandoren, Stefan
We investigate quantum corrections to the effective action of the universal hypermultiplet in the language of projective superspace. We rederive the recently found one-loop correction to the...
N = 2 supergravity in five dimensions revisited (2004)
Vandoren, Stefan, Gheerardyn, Jos, Wit, Tim De, Cucu, Sorin, Bergshoeff, Eric, Proeyen, Antoine Van
We construct matter-coupled N = 2 supergravity in five dimensions, using the superconformal approach. For the matter sector we take an arbitrary number of vector, tensor and hypermultiplets. By...
Non-extremal D-instantons (2004)
Roest, Diederik, Gran, Ulf, Collinucci, Andres, Bergshoeff, Eric, Vandoren, Stefan
We construct the most general non-extremal deformation of the D-instanton solution with maximal rotational symmetry. The general non-supersymmetric solution carries electric charges of the SL(2,R)...
N=2 Supersymmetric Scalar-Tensor Couplings (2003)
Theis, Ulrich, Vandoren, Stefan
We determine the general coupling of a system of scalars and antisymmetric tensors, with at most two derivatives and undeformed gauge transformations, for both rigid and local N=2 supersymmetry in...
Proceedings of the European workshop on the quantum structure of spacetime - Editorial (2003)
Billo, Marco, Henneaux, Marc, Sevrin, Alexander, Theisen, Stefan, Troost, Walter, Vandoren, Stefan, ...
The third yearly conference of the European Research and Training Network on the Quantum Structure of Spacetime and the Geometric Nature of Fundamental Interactions was held in Leuven, 13-19...
Instantons in the Double-Tensor Multiplet (2002)
Theis, Ulrich, Vandoren, Stefan
The double-tensor multiplet naturally appears in type IIB superstring compactifications on Calabi-Yau threefolds, and is dual to the universal hypermultiplet. We revisit the calculation of instanton...
Superconformal N=2, D=5 matter with and without actions (2002)
Bergshoeff, Eric, Cucu, Sorin, De Wit, Tim, Gheerardyn, Jos, Halbersma, Rein, Vandoren, Stefan, ...
We investigate N=2, D=5 supersymmetry and matter-coupled supergravity theories in a superconformal context. In a first stage we do not require the existence of a Lagrangian. Under this assumption, we...
Hyperkahler Cones and Orthogonal Wolf Spaces (2002)
Anguelova, Lilia, Rocek, Martin, Vandoren, Stefan
We construct the hyperkahler cones corresponding to the Quaternion-Kahler orthogonal Wolf spaces SO(n+4)/(SO(n)xSO(4)) and their non-compact versions, which appear in hypermultiplet couplings to N=2...
Superconformal N = 2, D = 5 matter with and without actions (2002)
Proeyen, Antoine Van, Gheerardyn, Jos, Cucu, Sorin, Halbersma, Rein, Wit, Tim De, Bergshoeff, Eric, ...
We investigate N = 2, D = 5 supersymmetry and matter-coupled supergravity theories in a superconformal context. In a first stage we do not require the existence of a lagrangian. Under this...
Gauging Isometries on Hyperkahler Cones and Quaternion-Kahler Manifolds (2001)
De Wit, Bernard, Rocek, Martin, Vandoren, Stefan
We extend our previous results on the relation between quaternion-Kahler manifolds and hyperkahler cones and we describe how isometries, moment maps and scalar potentials descend from the cone to the...
Hypermultiplets, Hyperkahler Cones and Quaternion-Kahler Geometry (2001)
De Wit, Bernard, Rocek, Martin, Vandoren, Stefan
We study hyperkahler cones and their corresponding quaternion-Kahler spaces. We present a classification of 4(n-1)-dimensional quaternion-Kahler spaces with n abelian quaternionic isometries, based...
New instantons in the double-well potential (2000)
Vandoren, Stefan, Van Nieuwenhuizen, Peter
A new instanton solution is found in the quantum-mechanical double-well potential with a four-fermion term. The solution has finite action and depends on four fermionic collective coordinates. We...
Instantons and Quaternions (2000)
We relate the moduli space of Yang-Mills instantons to quaternionic manifolds. For instanton number one, the Wolf spaces play an important role. We apply these ideas to instanton calculations in N=4...
Superconformal Hypermultiplets (1999)
De Wit, Bernard, Kleijn, Bas, Vandoren, Stefan
We present theories of N=2 hypermultiplets in four spacetime dimensions that are invariant under rigid or local superconformal symmetries. The target spaces of theories with rigid superconformal...
Rigid N=2 superconformal hypermultiplets (1998)
De Wit, Bernard, Kleijn, Bas, Vandoren, Stefan
We discuss superconformally invariant systems of hypermultiplets coupled to gauge fields associated with target-space isometries.
Gauging Conformal Algebras with Relations between the Generators (1995)
Thielemans, Kris, Vandoren, Stefan
We investigate the gauging of conformal algebras with relations between the generators. We treat the $W_{5/2}$--algebra as a specific example. We show that the gauge-algebra is in general reducible...