Publications (102)380.85 Total impact
 [Show abstract] [Hide abstract]
ABSTRACT: We give a systematic description of all warped $AdS_n$ and ${\mathbb{R}}^{n1,1}$ backgrounds of Mtheory and identify the a priori number of supersymmetries that these backgrounds preserve. In particular, we show that $AdS_n$ backgrounds preserve $N= 2^{[{n\over2}]} k$ for $n\leq4$ and $N= 2^{[{n\over2}]+1} k$ for $4<n\leq 7$ supersymmetries while ${\mathbb{R}}^{n1,1}$ backgrounds preserve $N= 2^{[{n\over2}]} k$ for $n\leq4$ and $N= 2^{[{n+1\over2}]} k$ for $4<n\leq7$, supersymmetries. Furthermore for $AdS_n$ backgrounds that satisfy the requirements for the maximum principle to hold, we show that the Killing spinors can be identified with the zero modes of Diraclike operators on $M^{11n}$ coupled to fluxes thus establishing a new class of Lichnerowicz type theorems. We also demonstrate that the Killing spinors of generic warped $AdS_n$ backgrounds do not factorize into products of Killing spinors on $AdS_n$ and Killing spinors on the transverse space.07/2014;  [Show abstract] [Hide abstract]
ABSTRACT: The spinorial geometry method of solving Killing spinor equations is reviewed as it applies to 6dimensional (1,0) supergravity. In particular, it is explained how the method is used to identify both the fractions of supersymmetry preserved by and the geometry of all supersymmetric backgrounds. Then two applications are described to systems that exhibit superconformal symmetry. The first is the proof that some 6dimensional black hole horizons are locally isometric to $AdS_3\times \Sigma^3$, where $\Sigma^3$ is diffeomeorphic to $S^3$. The second one is a description of all supersymmetric solutions of 6dimensional (1,0) superconformal theories and in particular of their brane solitons.Classical and Quantum Gravity 04/2014; 31(12). · 3.56 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We investigate the patching of double and exceptional field theories. In double field theory the patching conditions imposed on the spacetime 3form field strength $H$ after solving the strong section condition imply that $H$ is exact. A similar conclusion can be reached for the form field strengths of exceptional field theories after some plausive assumptions are made on the relation between the transition functions of the additional coordinates and the patching data of the form field strengths. We illustrate the issues that arise, and explore several alternative options including the introduction of Cfolds and of the topological geometrisation condition.02/2014;  [Show abstract] [Hide abstract]
ABSTRACT: IIA supergravity backgrounds preserving one supersymmetry locally admit four types of Killing spinors distinguished by the orbits of $Spin(9,1)$ on the space of spinors. We solve the Killing spinor equations of IIA supergravity with and without cosmological constant for Killing spinors representing two of these orbits, with isotropy groups $Spin(7)$ and $Spin(7)\ltimes\mathbb{R}^8$. In both cases, we identify the geometry of spacetime and express the fluxes in terms of the geometry. We find that the geometric constraints of backgrounds with a $Spin(7)\ltimes\mathbb{R}^8$ invariant Killing spinor are identical to those found for heterotic backgrounds preserving one supersymmetry.01/2014;  [Show abstract] [Hide abstract]
ABSTRACT: We solve the Killing spinor equations of 6dimensional (1,0) superconformal theories which include hypermultiplets in all cases. We show that the solutions preserve 1,2,3,4 and 8 supersymmetries. We find models with selfdual string solitons which are smooth and supported by instantons with an arbitrary gauge group, and 3brane solitons as expected from the Mbrane intersection rules.07/2013;  [Show abstract] [Hide abstract]
ABSTRACT: We show that the number of supersymmetries of IIB black hole horizons is N=2 N_ + 2 index(D_\lambda), where index(D_\lambda) is the index of the Dirac operator twisted with the line bundle \lambda^{1/2} of IIB scalars, and N_ is the dimension of the kernel of a horizon Dirac operator which depends on IIB fluxes. Therefore, all IIB horizons preserve an even number of supersymmetries. In addition if the horizons have nontrivial fluxes and N_ is nonzero, then index(D_\lambda) is nonnegative, and the horizons admit an sl(2,R) symmetry subalgebra. This provides evidence that all such horizons have an AdS/CFT dual. Furthermore if the orbits of sl(2,R) are twodimensional, the IIB horizons are warped products AdS_2 X S.Journal of High Energy Physics 06/2013; 2013(5). · 5.62 Impact Factor 
Article: IIB horizons
[Show abstract] [Hide abstract]
ABSTRACT: We solve the Killing spinor equations for all nearhorizon IIB geometries which preserve at least one supersymmetry. We show that generic horizon sections are 8dimensional almost Hermitian spin${}_c$ manifolds. Special cases include horizon sections with a $Spin(7)$ structure and those for which the Killing spinor is pure. We also explain how the common sector horizons and the horizons with only 5form flux are included in our general analysis. We investigate several special cases mainly focusing on the horizons with constant scalars admitting a pure Killing spinor and find that some of these exhibit a generalization of the 2SCYT condition that arises in the horizons with 5form fluxes only. We use this to construct new examples of nearhorizon geometries with both 3form and 5form fluxes.Classical and Quantum Gravity 04/2013; · 3.56 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We prove that the nearhorizon geometries of minimal gauged fivedimensional supergravity preserve at least half of the supersymmetry. If the nearhorizon geometries preserve a larger fraction, then they are locally isometric to AdS5. Our proof is based on Lichnerowicz type theorems for two horizon Dirac operators constructed from the supercovariant connection restricted to the horizon sections, and on an application of the index theorem. An application is that all fivedimensional horizons admit an sl(2,R) symmetry subalgebra.03/2013;  [Show abstract] [Hide abstract]
ABSTRACT: We find under some mild assumptions that the most general potential of 1dimensional conformal systems with time independent couplings is expressed as $V=V_0+V_1$, where $V_0$ is a homogeneous function with respect to a homothetic motion in configuration space and $V_1$ is determined from an equation with source a homothetic potential. Such systems admit at most an $SL(2,\bR)$ conformal symmetry which, depending on the couplings, is embedded in Diff(R)$ in three different ways. In one case, $SL(2,\bR)$ is also embedded in Diff(S^1). Examples of such models include those with potential $V=\alpha x^2+\beta x^{2}$ for arbitrary couplings $\alpha$ and $\beta$, the Calogero models with harmonic oscillator couplings and nonlinear models with suitable metrics and potentials. In addition, we give the conditions on the couplings for a class of gauge theories to admit a $SL(2,\bR)$ conformal symmetry. We present examples of such systems with general gauge groups and global symmetries that include the isometries of $AdS_2 x S^3$ and $AdS_2 x S^3 x S^3$ which arise as backgrounds in $AdS_2/CFT_1$.Classical and Quantum Gravity 10/2012; 30(7). · 3.56 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We solve the Killing spinor equations of 6dimensional (1,0) superconformal theories in all cases. In particular, we derive the conditions on the fields imposed by the Killing spinor equations and demonstrate that these depend on the isotropy group of the Killing spinors. We focus on the models proposed by Samtleben et al in \cite{ssw} and find that there are solutions preserving 1,2, 4 and 8 supersymmetries. We also explore the solutions which preserve 4 supersymmetries and find that many models admit string and 3brane solitons as expected from the Mbrane intersection rules. The string solitons are smooth regulated by the moduli of instanton configurations.Journal of High Energy Physics 04/2012; 2012(7). · 5.62 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We show that the supersymmetric near horizon black hole geometries of sixdimensional supergravity coupled to any number of scalar and tensor multiplets are either locally AdS3 × Σ3, where Σ3 is a homology 3sphere, or , where is a 4manifold whose geometry depends on the hypermultiplet scalars. In both cases, we find that the tensorini multiplet scalars are constant and the associated 3form field strengths vanish. We also demonstrate that the AdS3 × Σ3 horizons preserve two, four and eight supersymmetries. For horizons with four supersymmetries, Σ3 is in addition a nontrivial circle fibration over a topological 2sphere. The near horizon geometries preserving eight supersymmetries are locally isometric to either AdS3 × S3 or R1, 1 × T4. Moreover, we show that the horizons preserve one, two and four supersymmetries and the geometry of is Riemann, Kähler and hyperKähler, respectively.Classical and Quantum Gravity 02/2012; 29(5):055002. · 3.56 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We determine the geometry of the target spaces of supersymmetric nonrelativistic particles with torsion and magnetic couplings, and with symmetries generated by the fundamental forms of Gstructures for $G= U(n), SU(n), Sp(n), Sp(n)\cdot Sp(1), G_2$ and $Spin(7)$. We find that the KillingYano equation, which arises as a condition for the invariance of the worldline action, does not always determine the torsion coupling uniquely in terms of the metric and fundamental forms. We show that there are several connections with skewsymmetric torsion for $G=U(n), SU(n)$ and $G_2$ that solve the invariance conditions. We describe all these compatible connections for each of the $G$structures and explain the geometric nature of the couplings.Classical and Quantum Gravity 11/2011; 29(11). · 3.56 Impact Factor 
Article: ASPECTS OF SPINORIAL GEOMETRY
[Show abstract] [Hide abstract]
ABSTRACT: We review some aspects of the spinorial geometry approach to the classification of supersymmetric solutions of supergravity theories. In particular, we explain how spinorial geometry can be used to express the Killing spinor equations in terms of a linear system for the fluxes and the geometry of spacetime. The solutions of this linear system express some of the fluxes in terms of the spacetime geometry and determine the conditions on the spacetime geometry imposed by supersymmetry. We also present some of the recent applications like the classification of maximally supersymmetric Gbackgrounds in IIB, this includes the most general ppwave solution preserving 1/2 supersymmetry, and the classification of N = 31 backgrounds in ten and eleven dimensions.Modern Physics Letters A 11/2011; 22(01). · 1.11 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We utilize the classification of IIB horizons with 5form flux to present a unified description for the geometry of AdS_n, n=3,5,7 solutions. In particular, we show that all such backgrounds can be constructed from 8dimensional 2strong CalabiYau geometries with torsion which admit some additional isometries. We explore the geometry of AdS_3 and AdS_5 solutions but we do not find AdS_7 solutions.Classical and Quantum Gravity 10/2011; · 3.56 Impact Factor 
Article: Static Mhorizons
[Show abstract] [Hide abstract]
ABSTRACT: We determine the geometry of all static black hole horizons of Mtheory preserving at least one supersymmetry. We demonstrate that all such horizons are either warped products R^{1,1} *_w S or AdS_2 *_w S, where S admits an appropriate Spin(7) or SU(4) structure respectively; and we derive the conditions imposed by supersymmetry on these structures. We show that for electric static horizons with Spin(7) structure, the near horizon geometry is a product R^{1,1} * S, where S is a compact Spin(7) holonomy manifold. For electric static solutions with SU(4) structure, we show that the horizon section S is a circle fibration over an 8dimensional Kahler manifold which satisfies an additional condition involving the Ricci scalar and the length of the Ricci tensor. Solutions include AdS_2 * S^3 * CY_6 as well as many others constructed from taking the 8dimensional Kahler manifold to be a product of KahlerEinstein and CalabiYau spaces.Journal of High Energy Physics 06/2011; · 5.62 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We classify under some assumptions the IIB black hole horizons with 5form flux preserving more than 2 supersymmetries. We find that the spatial horizon sections with nonvanishing flux preserving 4 supersymmetries are locally isometric either to S^1 * S^3 * T^4 or to S^1 * S^3 * K_3 and the associated near horizon geometries are locally isometric to AdS_3 * S^3 * T^4 and AdS_3 * S^3 * K_3$, respectively. The near horizon geometries preserving more than 4 supersymmetries are locally isometric to R^{1,1} * T^8.Journal of High Energy Physics 04/2011; 9. · 5.62 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We solve the Killing spinor equations of sixdimensional (1, 0)supergravity coupled to any number of tensor, vector and scalar multiplets in all cases. The isotropy groups of Killing spinors are , , , Sp(1)(2), U(1)(4) and {1}(8), where in parenthesis is the number of supersymmetries preserved in each case. If the isotropy group is noncompact, the spacetime admits a parallel null 1form with respect to a connection with torsion given by the 3form field strength of the gravitational multiplet. The associated vector field is Killing and the 3form is determined in terms of the geometry of spacetime. The case admits a descendant solution preserving three out of four supersymmetries due to the hyperini Killing spinor equation. If the isotropy group is compact, the spacetime admits a natural frame constructed from 1form spinor bilinears. In the Sp(1) and U(1) cases, the spacetime admits three and four parallel 1forms with respect to the connection with torsion, respectively. The associated vector fields are Killing and under some additional restrictions the spacetime is a principal bundle with fibre a Lorentzian Lie group. The conditions imposed by the Killing spinor equations on all other fields are also determined.Classical and Quantum Gravity 04/2011; 28(10):105001. · 3.56 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We investigate the near horizon geometry of IIB supergravity black holes with nonvanishing 5form flux preserving at least two supersymmetries. We demonstrate that there are three classes of solutions distinguished by the choice of Killing spinors. We find that the spatial horizon sections of the class of solutions with an SU(4) invariant pure Killing spinor are hermitian manifolds and admit a hidden Kahler with torsion (KT) geometry compatible with the SU(4) structure. Moreover the Bianchi identity of the 5form, which also implies the field equations, can be expressed in terms of the torsion H as d(\omega\wedge H)=\partial\bar\partial \omega^2=0, where omega is a Hermitian form. We give several examples of near horizon geometries which include group manifolds, group fibrations over KT manifolds and uplifted geometries of lower dimensional black holes. Furthermore, we show that the class of solutions associated with a Spin(7) invariant spinor is locally a product R^{1,1} x S, where S is a holonomy Spin(7) manifold.Journal of High Energy Physics 01/2011; 2011(5). · 5.62 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We simplify the classification of supersymmetric solutions with compact holonomy of the Killing spinor equations of heterotic supergravity using the field equations and the additional assumption that the 3form flux is closed. We determine all the fractions of supersymmetry that the solutions preserve and find that there is a restriction on the number of supersymmetries which depends on the isometry group of the background. We examine the geometry of spacetime in all cases. We find that the supersymmetric solutions of heterotic supergravity are associated with a large number of geometric structures which include sevendimensional manifolds with G2 structure, sixdimensional complex and almost complex manifolds, and fourdimensional hyperKähler, Kähler and antiselfdual Weyl manifolds.Classical and Quantum Gravity 04/2010; 27(12):125008. · 3.56 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: All supersymmetric , D = 4 supergravity horizons have toroidal or spherical topology, irrespective of whether the black hole preserves any supersymmetry.Journal of High Energy Physics 01/2010; 2010(11):118. · 5.62 Impact Factor
Publication Stats
3k  Citations  
380.85  Total Impact Points  
Top Journals
Institutions

1987–2013

King's College London
 Department of Mathematics
Londinium, England, United Kingdom


2008

Chalmers University of Technology
 Department of Fundamental Physics
Göteborg, Vaestra Goetaland, Sweden


1993–2006

University of Cambridge
 Department of Applied Mathematics and Theoretical Physics
Cambridge, England, United Kingdom 
University of Melbourne
 School of Physics
Melbourne, Victoria, Australia


1997

Stanford University
 Department of Physics
Palo Alto, California, United States


1996

University of Groningen
 Centre for Theoretical Physics (CTN)
Groningen, Groningen, Netherlands


1988–1996

CERN
 Physics Department (PH)
Genève, Geneva, Switzerland


1994

Universität Hamburg
 II. Institut für Theoretische Physik
Hamburg, Hamburg, Germany


1986–1992

Imperial College London
 Department of Physics
Londinium, England, United Kingdom


1991

Queen Mary, University of London
Londinium, England, United Kingdom
