Holographic Superconductors from Gauged Supergravity

We consider minimal setups arising from different truncations of N=8 five-dimensional SO(6) gauged supergravity to study phase transitions involving spontaneous breaking of any of the U(1) symmetries in U(1)xU(1)xU(1)in SO(6). These truncations only keep the three relevant vector fields, four complex scalar fields carrying U(1) charges, plus two neutral scalar fields required by consistency. By considering thermal ensembles with different fixed U(1) charge densities and solving the complete equations including the full back-reaction, in some cases we find instabilities towards the formation of hairy black holes, which lead to second order transitions, resulting from a thermodynamical competition between different sectors. We argue that these should be the dominant thermodynamical instabilities in the full ten-dimensional type IIB theory. In other cases we find unstable branches of hairy black holes that extend to temperatures above a critical temperature (`retrograde condensation'). The results can be used as a first step to understand new aspects of the phase diagram of large N, N=4 SU(N) super Yang-Mills theory with fixed charge densities.Comment: 25 pages, 10 figures. v3: typo corrected in eq. (2.18

N=31 is not IIB

We adapt the spinorial geometry method to investigate supergravity backgrounds with near maximal number of supersymmetries. We then apply the formalism to show that the IIB supergravity backgrounds with 31 supersymmetries preserve an additional supersymmetry and so they are maximally supersymmetric. This rules out the existence of IIB supergravity preons.Comment: 7 page

Geometry of all supersymmetric type I backgrounds

We find the geometry of all supersymmetric type I backgrounds by solving the gravitino and dilatino Killing spinor equations, using the spinorial geometry technique, in all cases. The solutions of the gravitino Killing spinor equation are characterized by their isotropy group in Spin(9,1), while the solutions of the dilatino Killing spinor equation are characterized by their isotropy group in the subgroup Sigma(P) of Spin(9,1) which preserves the space of parallel spinors P. Given a solution of the gravitino Killing spinor equation with L parallel spinors, L = 1,2,3,4,5,6,8, the dilatino Killing spinor equation allows for solutions with N supersymmetries for any 0 < N =< L. Moreover for L = 16, we confirm that N = 8,10,12,14,16. We find that in most cases the Bianchi identities and the field equations of type I backgrounds imply a further reduction of the holonomy of the supercovariant connection. In addition, we show that in some cases if the holonomy group of the supercovariant connection is precisely the isotropy group of the parallel spinors, then all parallel spinors are Killing and so there are no backgrounds with N < L supersymmetries.Comment: 73 pages. v2: minor changes, references adde

Classical resolution of singularities in dilaton cosmologies

For models of dilaton-gravity with a possible exponential potential, such as the tensor-scalar sector of IIA supergravity, we show how cosmological solutions correspond to trajectories in a 2D Milne space (parametrized by the dilaton and the scale factor). Cosmological singularities correspond to points at which a trajectory meets the Milne horizon, but the trajectories can be smoothly continued through the horizon to an instanton solution of the Euclidean theory. We find some exact cosmology/instanton solutions that lift to black holes in one higher dimension. For one such solution, the singularities of a big crunch to big bang transition mediated by an instanton phase lift to the black hole and cosmological horizons of de Sitter Schwarzschild spacetimes.Comment: 24 pages, 2 figure

Maximally supersymmetric G-backgrounds of IIB supergravity

We classify the geometry of all supersymmetric IIB backgrounds which admit the maximal number of $G$-invariant Killing spinors. For compact stability subgroups $G=G_2, SU(3)$ and SU(2), the spacetime is locally isometric to a product $X_n\times Y_{10-n}$ with $n=3,4,6$, where $X_n$ is a maximally supersymmetric solution of a $n$-dimensional supergravity theory and $Y_{10-n}$ is a Riemannian manifold with holonomy $G$. For non-compact stability subgroups, G=K\ltimes\bR^8, $K=Spin(7)$, SU(4), $Sp(2)$, $SU(2)\times SU(2)$ and $\{1\}$, the spacetime is a pp-wave propagating in an eight-dimensional manifold with holonomy $K$. We find new supersymmetric pp-wave solutions of IIB supergravity.Comment: 22 page

The Classification of Highly Supersymmetric Supergravity Solutions

The spinorial geometry method is an effective method for constructing systematic classifications of supersymmetric supergravity solutions. Recent work on analysing highly supersymmetric solutions in type IIB supergravity using this method is reviewed [arXiv:hep-th/0606049, arXiv:0710.1829]. It is shown that all supersymmetric solutions of IIB supergravity with more than 28 Killing spinors are locally maximally supersymmetric.Comment: 23 pages, latex. To appear in the proceedings of the Special Metrics and Supersymmetry conference at Universidad del Pais Vasco, May 2008. References correcte

Fracture Toughness Of Nanoscale Zirconia Coatings On Titanium Substrates

In the biomedical field, the surface modification of titanium aims to inhibit wear, reduce corrosion and ion release, and promote biocompatibility. Sol-gel-derived ceramic nanoscale coatings show promise due to their relative ease of production, ability to form a physically and chemically uniform coating over complex geometric shapes, and their potential to deliver exceptional mechanical properties due to their nanocrystalline structure. In this study zirconia coatings on titanium were investigated for their fracture toughness

Cosmological D-instantons and Cyclic Universes

For models of gravity coupled to hyperbolic sigma models, such as the metric-scalar sector of IIB supergravity, we show how smooth trajectories in the `augmented target space' connect FLRW cosmologies to non-extremal D-instantons through a cosmological singularity. In particular, we find closed cyclic universes that undergo an endless sequence of big-bang to big-crunch cycles separated by instanton `phases'. We also find `big-bounce' universes in which a collapsing closed universe bounces off its cosmological singularity to become an open expanding universe.Comment: 21 pages, 4 figures. v2: minor change

Study on the impact of regulation (EC) No 1/2005 on the protec-tion of animals during transport

The objective of the findings of an evaluation of Regulation (EC) 1/2005 was to provide a detailed assessment of the implementation of the Regulation (EC) and its impact on the animals being transported and on operators, with special reference to trade flows, navigation systems and the socio‐economic and regional implications