7,448 research outputs found

    Einstein-Weyl structures and Bianchi metrics

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    We analyse in a systematic way the (non-)compact four dimensional Einstein-Weyl spaces equipped with a Bianchi metric. We show that Einstein-Weyl structures with a Class A Bianchi metric have a conformal scalar curvature of constant sign on the manifold. Moreover, we prove that most of them are conformally Einstein or conformally K\"ahler ; in the non-exact Einstein-Weyl case with a Bianchi metric of the type VII0,VIIIVII_0, VIII or IXIX, we show that the distance may be taken in a diagonal form and we obtain its explicit 4-parameters expression. This extends our previous analysis, limited to the diagonal, K\"ahler Bianchi IXIX case.Comment: Latex file, 12 pages, a minor modification, accepted for publication in Class. Quant. Gra

    BPS Solitons in M5-Brane Worldvolume Theory with Constant Three-Form Field

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    We study BPS solutions for a self-dual string and a neutral string in M5-brane worldvolume theory with constant three-form field. We further generalize such solitons to superpose with a calibrated surface. We also study a traveling wave on a calibrated surface in the constant three-form field background.Comment: 12 pages, LaTeX, minor correction, added referenc

    Two-Dimensional Helioseismic Power, Phase, and Coherence Spectra of {\it Solar Dynamics Observatory} Photospheric and Chromospheric Observables

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    While the {\it Helioseismic and Magnetic Imager} (HMI) onboard the {\it Solar Dynamics Observatory} (SDO) provides Doppler velocity [VV], continuum intensity [ICI_C], and line-depth [LdLd] observations, each of which is sensitive to the five-minute acoustic spectrum, the {\it Atmospheric Imaging Array} (AIA) also observes at wavelengths -- specifically the 1600 and 1700 Angstrom bands -- that are partly formed in the upper photosphere and have good sensitivity to acoustic modes. In this article we consider the characteristics of the spatio--temporal Fourier spectra in AIA and HMI observables for a 15-degree region around NOAA Active Region 11072. We map the spatio--temporal-power distribution for the different observables and the HMI Line Core [ILI_L], or Continuum minus Line Depth, and the phase and coherence functions for selected observable pairs, as a function of position and frequency. Five-minute oscillation power in all observables is suppressed in the sunspot and also in plage areas. Above the acoustic cut-off frequency, the behaviour is more complicated: power in HMI ICI_C is still suppressed in the presence of surface magnetic fields, while power in HMI ILI_L and the AIA bands is suppressed in areas of surface field but enhanced in an extended area around the active region, and power in HMI VV is enhanced in a narrow zone around strong-field concentrations and suppressed in a wider surrounding area. The relative phase of the observables, and their cross-coherence functions, are also altered around the active region. These effects may help us to understand the interaction of waves and magnetic fields in the different layers of the photosphere, and will need to be taken into account in multi-wavelength local helioseismic analysis of active regions.Comment: 18 pages, 15 figures, to be published in Solar Physic

    Degenerate principal series of quantum Harish-Chandra modules

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    In this paper we study a quantum analogue of a degenerate principal series of Uqsun,nU_q \mathfrak{su}_{n,n}-modules (0<q<10<q<1) related to the Shilov boundary of the quantum n×nn \times n-matrix unit ball. We give necessary and sufficient conditions for the modules to be simple and unitarizable and investigate their equivalence. These results are q-analogues of known classical results on reducibility and unitarizability of SU(n,n)-modules obtained by Johnson, Sahi, Zhang, Howe and Tan.Comment: 33 pages, 4 figure

    Assessing MyPlate Familiarity and Typical Meal Composition using Food Models in Children Aged 7-13

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    The Dietary Guidelines for Americans serve as a basis for developing federal nutrition education materials for the public, such as MyPlate. MyPlate is a visual cue that uses food groups as a guide to building healthy plates at mealtime. The objective of this study was to determine factors associated with child familiarity with MyPlate guidelines and to determine if typical meals met MyPlate guidelines using food models. A convenience sample of 250 children (aged 7-13 years) and their parent/guardian were recruited at a local science and history museum. Children viewed a picture of the MyPlate icon and were asked to identify the picture. Next, participants used a nine-inch plate to build a typical meal (meals that they would regularly consume) from a buffet of food and beverages models (&gt;65 items to choose from). Research team members took photographs of the plates. A Registered Dietitian Nutritionist determined the percentage of plates that met MyPlate guidelines. Eighty-six percent of children recognized the MyPlate icon upon viewing the image; 7.6% could accurately identify the icon by name. When participants were asked to build a typical meal, however, only 3.43% met MyPlate guidelines. The results of this study suggest that despite being familiar with MyPlate, children built typical meals that did not meet MyPlate guidelines

    On duality symmetries of supergravity invariants

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    The role of duality symmetries in the construction of counterterms for maximal supergravity theories is discussed in a field-theoretic context from different points of view. These are: dimensional reduction, the question of whether appropriate superspace measures exist and information about non-linear invariants that can be gleaned from linearised ones. The former allows us to prove that F-term counterterms cannot be E7(7)-invariant in D=4, N=8 supergravity or E6(6)-invariant in D=5 maximal supergravity. This is confirmed by the two other methods which can also be applied to D=4 theories with fewer supersymmetries and allow us to prove that N=6 supergravity is finite at three and four loops and that N=5 supergravity is three-loop finite.Comment: Clarification of arguments and their consistency with higher dimensional divergences added, e.g. we prove the 5D 4L non-renormalisation theorem. The 4L N=6 divergence is also ruled out. References adde

    Prevalence of liver fluke on the West Coast

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    A study of all herds (n=430) supplying Westland Milk Co-op were tested with an IDEXX Bulk Milk Elisa (BME) (IDEXX Fasciolosis Verification, IDEXX Europe BV, Hoofdorp, The Netherlands) which characterises herds into intensities of infection (Nil, Low, Medium, Strong). These equate to liver fluke infection prevalence of 0%, 50% within the sampled herd. Overall, the distribution of herds as analysed in the autumn of 2017 was Nil=31%, Low=11%, Medium=14%, Strong=43%. It was notable that some regions had much higher levels of infection than others.fals

    Orthosymplectically invariant functions in superspace

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    The notion of spherically symmetric superfunctions as functions invariant under the orthosymplectic group is introduced. This leads to dimensional reduction theorems for differentiation and integration in superspace. These spherically symmetric functions can be used to solve orthosymplectically invariant Schroedinger equations in superspace, such as the (an)harmonic oscillator or the Kepler problem. Finally the obtained machinery is used to prove the Funk-Hecke theorem and Bochner's relations in superspace.Comment: J. Math. Phy
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