343 research outputs found

    Supersymmetric Wilson loops in two dimensions and duality

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    We classify bosonic N=(2,2)\mathcal{N}=(2,2) supersymmetric Wilson loops on arbitrary backgrounds with vector-like R-symmetry. These can be defined on any smooth contour and come in two forms which are universal across all backgrounds. We show that these Wilson loops, thanks to their cohomological properties, are all invariant under smooth deformations of their contour. At genus zero they can always be mapped to local operators and computed exactly with supersymmetric localisation. Finally, we find the precise map, under two-dimensional Seiberg-like dualities, of correlators of supersymmetric Wilson loops.Comment: 16 pages, 2 figures; v2: minor corrections, references added; v3: new section and appendix, references added, published versio

    Perturbative evaluation of circular 1/2 BPS Wilson loops in N = 6 Super Chern-Simons theories

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    We present a complete two-loop analysis of the quantum expectation value for circular BPS Wilson loops in ABJ(M) theories. We examine in details the 1/2 BPS case, that requires non-trivial fermionic couplings with the contour, finding perfect agreement with the exact matrix model answer at zero framing. The result is obtained through a careful application of DRED regularization scheme, combined with a judicious rearrangement of the relevant perturbative contributions that reduces the computation to simple integrals. We carefully analyze the contribution of fermions that is crucial for the consistency with the localization procedure and point out the arising of pivotal evanescent terms, discussing their meaning in relation to Ward identities.Comment: 32 pages, 5 figures, Referemces adde

    Using Ontologies for Semantic Data Integration

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    While big data analytics is considered as one of the most important paths to competitive advantage of today’s enterprises, data scientists spend a comparatively large amount of time in the data preparation and data integration phase of a big data project. This shows that data integration is still a major challenge in IT applications. Over the past two decades, the idea of using semantics for data integration has become increasingly crucial, and has received much attention in the AI, database, web, and data mining communities. Here, we focus on a specific paradigm for semantic data integration, called Ontology-Based Data Access (OBDA). The goal of this paper is to provide an overview of OBDA, pointing out both the techniques that are at the basis of the paradigm, and the main challenges that remain to be addressed

    The use of Rayleigh-wave ellipticity for site-specific hazard assessment and microzonation: application to the city of Lucerne, Switzerland

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    The sediments underlying the city of Lucerne (Switzerland) consisting of fluvio-lacustrine deposits of Quaternary age have the potential to produce strong amplification of the seismic wavefield. To obtain a reliable estimation of the deep soil structure, we combine different methodologies based on ambient noise recordings, such as single station horizontal to vertical ratios and three-component array analysis. Two novel techniques to estimate Rayleigh-wave ellipticity from ambient noise recordings are tested. These are based on a single- and a multistation approach, respectively. The first utilizes the continuous wavelet transform to perform a decomposition of the noise wavefield and to isolate and extract the Rayleigh-wave contribution. The second, conversely, relies on a high-resolution f-k method to achieve the same result. We compare the results from the two techniques to provide an evaluation of their capabilities and limitations. A two-step inversion scheme is then presented to improve resolution on the bedrock depth. In particular, the surface wave dispersion information is initially used to constrain the soft sediment part, while the Rayleigh-wave ellipticity peak is subsequently used for constraining the bedrock depth. It is shown that such an approach is beneficial to map the bedrock geometry over dense urban areas. The output velocity model is then used to compute the local seismic amplification by means of gridded 1-D approximatio

    Distal radius fractures: treatment using the Epibloc system.

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    Summary The Epibloc™ system of percutaneous endomedullary internal fixation is best indicated for AO type A2-3 extra-articular fractures of the distal radius and AO type C1 slightly comminuted articular fractures. This system includes pins that can be inserted into the medullary canal and advanced without breaking through the second cortex. This fixation is stabilised by an external plate and rendered dynamic by the pins' elasticity which compresses the fractured surfaces. Moreover, this system results in transversal ligamentotaxis which helps prevent secondary reduction losses. The result of a preliminary series of 326 cases is evaluated

    Unilateral NMR: a Noninvasive Tool for Monitoring In Situ the Effectiveness of Intervention to Reduce the Capillary Raise of Water in an Ancient Deteriorated Wall Painting

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    Portable unilateral NMR was used to quantitatively map in a fully noninvasive way the moisture distribution in an ancient deteriorated wall painting before and after an intervention to reduce the capillary raise of water through the wall. Maps obtained at a depth of 0.5 cm clearly showed the path of the capillary raise and indicated that, after the intervention, the moisture level was reduced. Maps obtained by measuring the first layers of the wall painting were affected by the critical environmental conditions of the second hypogeous level of St. Clement Basilica, Rome, and by the presence of salts efflorescence and encrustations on the surface of the wall painting. The morphology and the elemental composition of salts investigated by SEM-EDS indicated that efflorescences and encrustations were mostly constituted of gypsum and calcite. The presence of these salts is explained with the presence of high concentration of carbon dioxide and sulphur-rich particles due to pollution which, along with the high-moisture level and the extremely feeble air circulation, cause recarbonation and sulphation processes on the plaster surface

    Flow-volume curve analysis for predicting recurrence after endoscopic dilation of airway stenosis

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    The flow-volume curve is a simple test for diagnosing upper airway obstruction. We evaluated its use to predict recurrence in patients undergoing endoscopic dilation for treatment of benign upper airway stenosis

    Mastro: Ontology-Based Data Access at Work (Extended Abstract)

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    In this paper we present the current version of Mastro, a system for ontologybased data access (OBDA) developed at Sapienza UniversitĂ  di Roma. Mastro allows users for accessing external data sources by querying an ontology expressed in a fragment of the W3C Web Ontology Language (OWL). As in data integration [5], mappings are used in OBDA to specify the correspondence between a unified view of the domain (called global schema in data integration terminology) and the data stored at the sources. The distinguishing feature of the OBDA approach, however, is the fact that the global schema is specified using an ontology language, which typically allows to provide a rich conceptualization of the domain of interest, independently from the source representation
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