Non-Abelian pp-waves in D=4 supergravity theories

The non-Abelian plane waves, first found in flat spacetime by Coleman and subsequently generalized to give pp-waves in Einstein-Yang-Mills theory, are shown to be 1/2 supersymmetric solutions of a wide variety of N=1 supergravity theories coupled to scalar and vector multiplets, including the theory of SU(2) Yang-Mills coupled to an axion \sigma and dilaton \phi recently obtained as the reduction to four-dimensions of the six-dimensional Salam-Sezgin model. In this latter case they provide the most general supersymmetric solution. Passing to the Riemannian formulation of this theory we show that the most general supersymmetric solution may be constructed starting from a self-dual Yang-Mills connection on a self-dual metric and solving a Poisson equation for e^\phi. We also present the generalization of these solutions to non-Abelian AdS pp-waves which allow a negative cosmological constant and preserve 1/4 of supersymmetry.Comment: Latex, 1+12 page

The Influence of Selected Antecedents of Frontline Employee\u27s Perceptions of Service Recovery Performance

The purpose of this study is to determine the potential impact of selected organizational factors on boundary-spanning-role employees’ perceptions of service recovery performance. This study also aims to assess the impact of service recovery performance on the intention to leave the job and extrinsic job satisfaction. This study uses a sample of frontline employees in Belek, Antalya, Turkey. The empirical findings revealed that education, team work and role ambiguity as frontline job perceptions were found to exert positive influences on the service recovery performance, but, empowerment, reward, and organizational commitment were found to have negative effects on the service recovery performance

2-(1H-Benzimidazol-1-yl)-1-(2-fur­yl)ethanone O-ethyl­oxime

In the mol­ecule of the title compound, C15H15N3O2, the planar benzimidazole ring system [maximum deviation = 0.023 (2) Å] is oriented at a dihedral angle of 74.21 (5)° with respect to the furan ring. In the crystal structure, inter­molecular C—H⋯N inter­actions link the mol­ecules into centrosymmetric R 2 2(18) dimers. In addition, the structure is stabilized by π–π contacts between parallel imidazole rings [centroid–centroid distance = 3.726 (1) Å] and a weak C—H⋯π inter­action

On Montel and Montel–Popoviciu Theorems in Several Variables

We present an elementary proof of a general version of Montel’s theorem in several variables which is based on the use of tensor product polynomial interpolation. We also prove a Montel-Popoviciu’s type theorem for functions f:Rd→Rf:Rd→R for d \u3e 1. Furthermore, our proof of this result is also valid for the case d = 1, differing in several points from Popoviciu’s original proof. Finally, we demonstrate that our results are optimal

On Approximation Schemes and Compactness

We present an overview of some results about characterization of compactness in which the concept of approximation scheme has had a role. In particular, we present several results that were proved by the second author, jointly with Luther, a decade ago, when these authors were working on a very general theory of approximation spaces. We then introduce and show the basic properties of a new concept of compactness, which was studied by the first author in the eighties, by using a generalized concept of approximation scheme and its associated Kolmogorov numbers, which generalizes the classical concept of compactness

Spatial Distribution of the Incompressible Strips at Aharonov-Bohm Interferometer

In this work, the edge physics of an Aharonov-Bohm interferometer (ABI) defined on a two dimensional electron gas, subject to strong perpendicular magnetic field B, is investigated. We solve the three dimensional Poisson equation using numerical techniques starting from the crystal growth parameters and surface image of the sample. The potential profiles of etched and gate defined geometries are compared and it is found that the etching yields a steeper landscape. The spatial distribution of the incompressible strips is investigated as a function of the gate voltage and applied magnetic field, where the imposed current is confined to. AB interference is investigated due to scattering processes between two incompressible "edge-states".Comment: 5 pages, 3 figure

MANAGEMENT OF 20TH CENTURY HYDROELECTRIC PLANTS AS INDUSTRIAL HERITAGE

Abstract. By rapidly increasing the production of energy and widely extending the usage of electricity in the 20th century, hydroelectric plants and dams have radically affected the social, technological and industrial aspects of the period. Therefore, as an integral part of industrial heritage, the cultural assets of these energy facilities are required to be preserved. As a requirement of this hypothesis, it is necessary: to develop management strategies for these assets; to provide scientific data and information on these buildings / facilities; to define criteria of 'planned conservation' with long-term preventive measures in order to provide the continuation of the original function as long as possible. Hydroelectric plants are a common subject of interest for several disciplines, such as: engineering, hydrology, ecology, geo-sciences and remote sensing. Therefore, the conservation of the plants also requires the interdisciplinary study and collaboration of these disciplines.Within the study, the considerations of an interdisciplinary approach – such as dam safety, ecological concerns and energy requirements – are presented, and examples from different countries are examined through the framework of architectural conservation, considering cases of dam failures, intended removal of dams and upgrading of facilities. Preventive measures for the planned conservation of hydro electrical facilities such as: constant maintenance of technical components; management of the sediment accumulated in the reservoirs; methods of analysis for the structure of the embankment are introduced briefly, concentrating on gravity dams, in order to provide conclusions for the conservation of Sarıyar Dam and Hydroelectric Plant (1956) in Turkey.</p

Chiral supersymmetric pp-wave solutions of IIA supergravity

We describe solutions of type IIA (N=2, D=10) supergravity built under the assumption of the existence of at least one residual chiral supersymmetry. Their geometry is of pp-wave type. Explicit parametrization of the metric and matter field components, in terms of Killing spinors and arbitrary functions, is provided.Comment: LaTeX file, 10 page

The general form of supersymmetric solutions of N=(1,0) U(1) and SU(2) gauged supergravities in six dimensions

We obtain necessary and sufficient conditions for a supersymmetric field configuration in the N=(1,0) U(1) or SU(2) gauged supergravities in six dimensions, and impose the field equations on this general ansatz. It is found that any supersymmetric solution is associated to an $SU(2)\ltimes \mathbb{R}^4$ structure. The structure is characterized by a null Killing vector which induces a natural 2+4 split of the six dimensional spacetime. A suitable combination of the field equations implies that the scalar curvature of the four dimensional Riemannian part, referred to as the base, obeys a second order differential equation. Bosonic fluxes introduce torsion terms that deform the $SU(2)\ltimes\mathbb{R}^4$ structure away from a covariantly constant one. The most general structure can be classified in terms of its intrinsic torsion. For a large class of solutions the gauge field strengths admit a simple geometrical interpretation: in the U(1) theory the base is K\"{a}hler, and the gauge field strength is the Ricci form; in the SU(2) theory, the gauge field strengths are identified with the curvatures of the left hand spin bundle of the base. We employ our general ansatz to construct new supersymmetric solutions; we show that the U(1) theory admits a symmetric Cahen-Wallach$_4\times S^2$ solution together with a compactifying pp-wave. The SU(2) theory admits a black string, whose near horizon limit is $AdS_3\times S_3$. We also obtain the Yang-Mills analogue of the Salam-Sezgin solution of the U(1) theory, namely $R^{1,2}\times S^3$, where the $S^3$ is supported by a sphaleron. Finally we obtain the additional constraints implied by enhanced supersymmetry, and discuss Penrose limits in the theories.Comment: 1+29 pages, late

A String and M-theory Origin for the Salam-Sezgin Model

An M/string-theory origin for the six-dimensional Salam-Sezgin chiral gauged supergravity is obtained, by embedding it as a consistent Pauli-type reduction of type I or heterotic supergravity on the non-compact hyperboloid ${\cal H}^{2,2}$ times $S^1$. We can also obtain embeddings of larger, non-chiral, gauged supergravities in six dimensions, whose consistent truncation yields the Salam-Sezgin theory. The lift of the Salam-Sezgin (Minkowski)$_4\times S^2$ ground state to ten dimensions is asymptotic at large distances to the near-horizon geometry of the NS5-brane.Comment: Latex, 18 pages; minor correction