The Geometry of D=11 Null Killing Spinors

We determine the necessary and sufficient conditions on the metric and the four-form for the most general bosonic supersymmetric configurations of D=11 supergravity which admit a null Killing spinor i.e. a Killing spinor which can be used to construct a null Killing vector. This class covers all supersymmetric time-dependent configurations and completes the classification of the most general supersymmetric configurations initiated in hep-th/0212008.Comment: 30 pages, typos corrected, reference added, new solution included in section 5.1; uses JHEP3.cl

Brane Resolution Through Fibration

We consider p-branes with one or more circular directions fibered over the transverse space. The fibration, in conjunction with the transverse space having a blown-up cycle, enables these p-brane solutions to be completely regular. Some such circularly-wrapped D3-brane solutions describe flows from SU(N)^3 N=2 theory, F_0 theory, as well as an infinite family of superconformal quiver gauge theories, down to three-dimensional field theories. We discuss the operators that are turned on away from the UV fixed points. Similarly, there are wrapped M2-brane solutions which describe smooth flows from known three-dimensional supersymmetric Chern-Simons matter theories, such as ABJM theory. We also consider p-brane solutions on gravitational instantons, and discuss various ways in which U-duality can be applied to yield other non-singular solutions.Comment: 35 pages, additional referenc

Flowing with Eight Supersymmetries in M-Theory and F-theory

We consider holographic RG flow solutions with eight supersymmetries and study the geometry transverse to the brane. For both M2-branes and for D3-branes in F-theory this leads to an eight-manifold with only a four-form flux. In both settings there is a natural four-dimensional hyper-Kahler slice that appears on the Coulomb branch. In the IIB theory this hyper-Kahler manifold encodes the Seiberg-Witten coupling over the Coulomb branch of a U(1) probe theory. We focus primarily upon a new flow solution in M-theory. This solution is first obtained using gauged supergravity and then lifted to eleven dimensions. In this new solution, the brane probes have an Eguchi-Hanson moduli space with the M2-branes spread over the non-trivial 2-sphere. It is also shown that the new solution is valid for a class of orbifold theories. We discuss how the hyper-Kahler structure on the slice extends to some form of G-structure in the eight-manifold, and describe how this can be computed.Comment: 29 pages, 1 figure, harvma

Supersymmetry breaking at the end of a cascade of Seiberg dualities

We study the IR dynamics of the cascading non-conformal quiver theory on N regular and M fractional D3 branes at the tip of the complex cone over the first del Pezzo surface. The horizon of this cone is the irregular Sasaki-Einstein manifold Y^{2,1}. Our analysis shows that at the end of the cascade supersymmetry is dynamically broken.Comment: 12 pages, 2 figures, minor changes, typos correcte

Gravity duals to deformed SYM theories and Generalized Complex Geometry

We analyze the supersymmetry conditions for a class of SU(2) structure backgrounds of Type IIB supergravity, corresponding to a specific ansatz for the supersymmetry parameters. These backgrounds are relevant for the AdS/CFT correspondence since they are suitable to describe mass deformations or beta-deformations of four-dimensional superconformal gauge theories. Using Generalized Complex Geometry we show that these geometries are characterized by a closed nowhere-vanishing vector field and a modified fundamental form which is also closed. The vector field encodes the information about the superpotential and the type of deformation - mass or beta respectively. We also show that the Pilch-Warner solution dual to a mass-deformation of N =4 Super Yang-Mills and the Lunin-Maldacena beta-deformation of the same background fall in our class of solutions.Comment: LaTex, 29 page

Are Mash-Ups the Future for Online Learning Platforms? Psychology A-Level Students' Judgements about VLE and MUPPLE Interfaces

Virtual Learning Environments (VLEs) have become ubiquitous in colleges and universities but have failed to consistently improve learning (Machin, 2007). An alternative interface can be provided in the form of a mashed-up personal learning environment (MUPPLE). The aim of this study was to investigate student perceptions of its desirability and utility in comparison to their existing VLE. A psychology-oriented MUPPLE was constructed using a free online mash-up platform. A focus group of psychology A-level students was asked to identify likely advantages and disadvantages of the MUPPLE as compared to their existing VLE interface. They identified five potential advantages of the MUPPLE interface; aesthetics, congruence with online apps used outside formal education, user control, utility as an aid to A-level study, and likely utility as an aid to undergraduate study. With regard to utility as an aid to A-level study, the focus group expressed concern that, whilst the MUPPLE interface would be likely to enhance independent study, that this might not in turn advantage A-level students. However, no advantages were attributed to the VLE interface. Sixty-five psychology A-level students assessed a MUPPLE and a VLE interface against the five criteria identified by the focus group. A within-subjects MANOVA revealed significant preferences for the MUPPLE interface on all five criteria. Implications for psychology education are discussed, and further research is called fo

New Einstein-Sasaki and Einstein Spaces from Kerr-de Sitter

In this paper, which is an elaboration of our results in hep-th/0504225, we construct new Einstein-Sasaki spaces L^{p,q,r_1,...,r_{n-1}} in all odd dimensions D=2n+1\ge 5. They arise by taking certain BPS limits of the Euclideanised Kerr-de Sitter metrics. This yields local Einstein-Sasaki metrics of cohomogeneity n, with toric U(1)^{n+1} principal orbits, and n real non-trivial parameters. By studying the structure of the degenerate orbits we show that for appropriate choices of the parameters, characterised by the (n+1) coprime integers (p,q,r_1,...,r_{n-1}), the local metrics extend smoothly onto complete and non-singular compact Einstein-Sasaki manifolds L^{p,q,r_1,...,r_{n-1}}. We also construct new complete and non-singular compact Einstein spaces \Lambda^{p,q,r_1,...,r_n} in D=2n+1 that are not Sasakian, by choosing parameters appropriately in the Euclideanised Kerr-de Sitter metrics when no BPS limit is taken.Comment: latex, 26 page

AdS spacetimes from wrapped D3-branes

We derive a geometrical characterisation of a large class of AdS_3 and AdS_2 supersymmetric spacetimes in IIB supergravity with non-vanishing five-form flux using G-structures. These are obtained as special cases of a class of supersymmetric spacetimes with an $\mathbb{R}^{1,1}$ or $\mathbb{R}$ (time) factor that are associated with D3-branes wrapping calibrated 2- or 3- cycles, respectively, in manifolds with SU(2), SU(3), SU(4) and G_2 holonomy. We show how two explicit AdS solutions, previously constructed in gauged supergravity, satisfy our more general G-structure conditions. For each explicit solution we also derive a special holonomy metric which, although singular, has an appropriate calibrated cycle. After analytic continuation, some of the classes of AdS spacetimes give rise to known classes of BPS bubble solutions with $\mathbb{R}\times SO(4)\times SO(4)$, $\mathbb{R}\times SO(4)\times U(1)$, and $\mathbb{R}\times SO(4)$ symmetry. These have 1/2, 1/4 and 1/8 supersymmetry, respectively. We present a new class of 1/8 BPS geometries with $\mathbb{R}\times SU(2)$ symmetry, obtained by analytic continuation of the class of AdS spacetimes associated with D3-branes wrapped on associative three-cycles.Comment: 1+30 pages; v2, references added; v3, typos corrected, reference adde

1/4-BPS M-theory bubbles with SO(3) x SO(4) symmetry

In this paper we generalize the work of Lin, Lunin and Maldacena on the classification of 1/2-BPS M-theory solutions to a specific class of 1/4-BPS configurations. We are interested in the solutions of 11 dimensional supergravity with $SO(3)\times SO(4)$ symmetry, and it is shown that such solutions are constructed over a one-parameter familiy of 4 dimensional almost Calabi-Yau spaces. Through analytic continuations we can obtain M-theory solutions having $AdS_2\times S^3$ or $AdS_3\times S^2$ factors. It is shown that our result is equivalent to the $AdS$ solutions which have been recently reported as the near-horizon geometry of M2 or M5-branes wrapped on 2 or 4-cycles in Calabi-Yau threefolds. We also discuss the hierarchy of M-theory bubbles with different number of supersymmetries.Comment: 22 pages, JHEP3.cls; v2. revised version. showed that our results agree with previous works hep-th/0605146 and hep-th/061219

The Geometry of D=11 Killing Spinors

We propose a way to classify all supersymmetric configurations of D=11 supergravity using the G-structures defined by the Killing spinors. We show that the most general bosonic geometries admitting a Killing spinor have at least a local SU(5) or an (Spin(7)\ltimes R^8)x R structure, depending on whether the Killing vector constructed from the Killing spinor is timelike or null, respectively. In the former case we determine what kind of local SU(5) structure is present and show that almost all of the form of the geometry is determined by the structure. We also deduce what further conditions must be imposed in order that the equations of motion are satisfied. We illustrate the formalism with some known solutions and also present some new solutions including a rotating generalisation of the resolved membrane solutions and generalisations of the recently constructed D=11 Godel solution.Comment: 36 pages. Typos corrected and discussion on G-structures improved. Final version to appear in JHE