Blocking of Dynamical Triangulations with Matter

We use the recently proposed node decimation algorithm for blocking dynamical geometries to investigate a class of models, with central charge greater than unity, coupled to 2D gravity. We demonstrate that the blocking preserves the fractal structure of the surfaces.Comment: Talk presented at LATTICE96(gravity), 3 pages, LaTeX, espcrc2.st

Stress-induced transformation in a Ni-Mn-In alloy and the concomitant change of resistivity

In this work, the influence of mechanical stress on magnetic properties and electric resistance of a Ni-Mn- In alloy was studied. It is shown that compression of Ni-Mn-In polycrystalline specimens brings about a stressinduced martensitic transformation. Optical images recorded in-situ confirmed the formation of a martensitic structure during loading and back-transformation upon unloading. Unloading after deformation of specimens that had experienced compressive strains up to 6%resulted in full recovery of their resistivity and magnetic susceptibility. The sharp increase in the electric resistance caused by the stress-induced transformation opens up new possibilities for Ni- Mn-In alloys to be used as a material for sensors responding to mechanical stress

An online analytical processing multi-dimensional data warehouse for malaria data

Malaria is a vector-borne disease that contributes substantially to the global burden of morbidity and mortality. The management of malaria-related data from heterogeneous, autonomous, and distributed data sources poses unique challenges and requirements. Although online data storage systems exist that address specific malaria-related issues, a globally integrated online resource to address different aspects of the disease does not exist. In this article, we describe the design, implementation, and applications of a multidimensional, online analytical processing data warehouse, named the VecNet Data Warehouse (VecNet-DW). It is the first online, globally-integrated platform that provides efficient search, retrieval and visualization of historical, predictive, and static malaria-related data, organized in data marts. Historical and static data are modelled using star schemas, while predictive data are modelled using a snowflake schema. The major goals, characteristics, and components of the DW are described along with its data taxonomy and ontology, the external data storage systems and the logical modelling and physical design phases. Results are presented as screenshots of a Dimensional Data browser, a Lookup Tables browser, and a Results Viewer interface. The power of the DW emerges from integrated querying of the different data marts and structuring those queries to the desired dimensions, enabling users to search, view, analyse, and store large volumes of aggregated data, and responding better to the increasing demands of users

Higher-Derivative Terms in N=2 Supersymmetric Effective Actions

We show how to systematically construct higher-derivative terms in effective actions in harmonic superspace despite the infinite redundancy in their description due to the infinite number of auxiliary fields. Making an assumption about the absence of certain superspace Chern-Simons-like terms involving vector multiplets, we write all 3- and 4-derivative terms on Higgs, Coulomb, and mixed branches. Among these terms are several with only holomorphic dependence on fields, and at least one satisfies a non-renormalization theorem. These holomorphic terms include a novel 3-derivative term on mixed branches given as an integral over 3/4 of superspace. As an illustration of our method, we search for Wess-Zumino terms in the low energy effective action of N=2 supersymmetric QCD. We show that such terms occur only on mixed branches. We also present an argument showing that the combination of space-time locality with supersymmetry implies locality in the anticommuting superspace coordinates of for unconstrained superfields.Comment: 30 pages. Added references and simplified final form of WZ ter

Analysis of the vector and axialvector BcB_c mesons with QCD sum rules

In this article, we study the vector and axialvector $B_c$ mesons with the QCD sum rules, and make reasonable predictions for the masses and decay constants, then calculate the leptonic decay widths. The present predictions for the masses and decay constants can be confronted with the experimental data in the future. We can also take the masses and decay constants as basic input parameters and study other phenomenological quantities with the three-point vacuum correlation functions via the QCD sum rules.Comment: 14 pages, 16 figure

Bubbles from Nothing

Within the framework of flux compactifications, we construct an instanton describing the quantum creation of an open universe from nothing. The solution has many features in common with the smooth 6d bubble of nothing solutions discussed recently, where the spacetime is described by a 4d compactification of a 6d Einstein-Maxwell theory on S^2 stabilized by flux. The four-dimensional description of this instanton reduces to that of Hawking and Turok. The choice of parameters uniquely determines all future evolution, which we additionally find to be stable against bubble of nothing instabilities.Comment: 19 pages, 6 figure

Relating the Cosmological Constant and Supersymmetry Breaking in Warped Compactifications of IIB String Theory

It has been suggested that the observed value of the cosmological constant is related to the supersymmetry breaking scale M_{susy} through the formula Lambda \sim M_p^4 (M_{susy}/M_p)^8. We point out that a similar relation naturally arises in the codimension two solutions of warped space-time varying compactifications of string theory in which non-isotropic stringy moduli induce a small but positive cosmological constant.Comment: 7 pages, LaTeX, references added and minor changes made, (v3) map between deSitter and global cosmic brane solutions clarified, supersymmetry breaking discussion improved and references adde

BPS Domain Wall Junctions in Infinitely Large Extra Dimensions

We consider models of scalar fields coupled to gravity which are higher-dimensional generalizations of four dimensional supergravity. We use these models to describe domain wall junctions in an anti-de Sitter background. We derive Bogomolnyi equations for the scalar fields from which the walls are constructed and for the metric. From these equations a BPS-like formula for the junction energy can be derived. We demonstrate that such junctions localize gravity in the presence of more than one uncompactified extra dimension.Comment: 17 pages, uses RevTeX, new references adde

Exact Black Holes and Gravitational Shockwaves on Codimension-2 Branes

We derive exact gravitational fields of a black hole and a relativistic particle stuck on a codimension-2 brane in $D$ dimensions when gravity is ruled by the bulk $D$-dimensional Einstein-Hilbert action. The black hole is locally the higher-dimensional Schwarzschild solution, which is threaded by a tensional brane yielding a deficit angle and includes the first explicit example of a `small' black hole on a tensional 3-brane. The shockwaves allow us to study the large distance limits of gravity on codimension-2 branes. In an infinite locally flat bulk, they extinguish as $1/r^{D-4}$, i.e. as $1/r^2$ on a 3-brane in $6D$, manifestly displaying the full dimensionality of spacetime. We check that when we compactify the bulk, this special case correctly reduces to the 4D Aichelburg-Sexl solution at large distances. Our examples show that gravity does not really obstruct having general matter stress-energy on codimension-2 branes, although its mathematical description may be more involved.Comment: 18 pages, LaTeX; v2: added references, version to appear in JHE

Scalar brane backgrounds in higher order curvature gravity

We investigate maximally symmetric brane world solutions with a scalar field. Five-dimensional bulk gravity is described by a general lagrangian which yields field equations containing no higher than second order derivatives. This includes the Gauss-Bonnet combination for the graviton. Stability and gravitational properties of such solutions are considered, and we particularily emphasise the modifications induced by the higher order terms. In particular it is shown that higher curvature corrections to Einstein theory can give rise to instabilities in brane world solutions. A method for analytically obtaining the general solution for such actions is outlined. Genericaly, the requirement of a finite volume element together with the absence of a naked singularity in the bulk imposes fine-tuning of the brane tension. A model with a moduli scalar field is analysed in detail and we address questions of instability and non-singular self-tuning solutions. In particular, we discuss a case with a normalisable zero mode but infinite volume element.Comment: published versio