2,405 research outputs found

    Smooth one-dimensional topological field theories are vector bundles with connection

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    We prove that smooth 1-dimensional topological field theories over a manifold are the same as vector bundles with connection. The main novelty is our definition of the smooth 1-dimensional bordism category, which encodes cutting laws rather than gluing laws. We make this idea precise through a smooth generalization of Rezk's complete Segal spaces. With such a definition in hand, we analyze the category of field theories using a combination of descent, a smooth version of the 1-dimensional cobordism hypothesis, and standard differential geometric arguments.Comment: 20 pages. Comments and questions are very welcom

    Extended field theories are local and have classifying spaces

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    We show that all extended functorial field theories, both topological and nontopological, are local. We define the smooth (infinity,d)-category of bordisms with geometric data, such as Riemannian metrics or geometric string structures, and prove that it satisfies codescent with respect to the target S, which implies the locality property. We apply this result to construct a classifying space for concordance classes of functorial field theories with geometric data, solving a conjecture of Stolz and Teichner about the existence of such a space. We use our classifying space construction to develop a geometric theory of power operations, following the recent work of Barthel, Berwick-Evans, and Stapleton.Comment: 40 pages. Comments and questions are welcom

    Three new goatfishes of the genus Upeneus (Mullidae) from the Indo-Pacific, with a redescription of colour patterns in U. margarethae

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    For the goatfish genus Upeneus Cuvier 1829 (Mullidae), a new taxonomic species group called the “margarethae group” is established which can be distinguished from the six species of the most similar “tragula group” by a combination of the following characteristics: absence of dark pigmentation in the area of the first dorsal-fin tip, 21–25 total gill rakers and 28–30 lateral-line scales. Initially, three recently-described species have been included in the margarethae group: Upeneus margarethae Uiblein & Heemstra, 2010, known from the Indian Ocean including the Red Sea and from the Arafura Sea (W Pacific), U. mouthami Randall & Kulbicki, 2006, from New Caledonia and Vanuatu (W Pacific), and U. randalli Uiblein & Heemstra, 2011, from the Arabian/Persian Gulf and the inner Gulf of Oman (NW Indian Ocean). The present taxonomic review of the margarethae group analyses a large data set of 41 morphometric, 10 meristic and many colour characters obtained from 279 preserved goatfish specimens and 166 fresh-colour photos (plus a fresh-colour drawing). For the nominal species of the group, U. margarethae, a redescription of the colour patterns is provided and new records for Myanmar, Andaman Sea (NE Indian Ocean) and the Gulf of Carpentaria, N Australia (W Pacific), are reported. Three new species are described: U. caudofasciatus n. sp. from the area of the Great Barrier Reef to Torres Strait off NE Australia (Coral Sea, W Pacific), U. gubal n. sp. from the S Gulf of Suez (Northern Red Sea), and U. heterospinus n. sp. from S Indonesia to Singapore, the Gulf of Thailand, Vietnam, Philippines, China, Taiwan and Japan (W Pacific). A comprehensive alpha-taxonomic approach is adopted, considering population differences as well as intraspecific size-related variation in morphology and colour patterns by splitting the data set into two size classes, adults (≥ 65 mm SL) and smaller subadults. Inter- and intraspecific comparisons include statistical analyses for species and population with sufficiently large samples sizes (n ≥ 20). Colour-pattern characterization and analysis are based on photos of recently collected and deceased fish (partly associated with voucher specimens), photos obtained from active or resting fishes in situ or in a tank, and inspection of pigmentation patterns retained in preserved specimens. Species differences are elaborated under consideration of distribution patterns and the characteristics found in the closest-most population of widely distributed species such as U. margarethae, resulting in clear and consistent distinction among the six species in single or in a combination of several characteristics. Comparisons among size classes revealed species-specific patterns in morphometric, meristic and colour changes with increasing size. One species, U. heterospinus n. sp., has seven or eight spines in the dorsal fin which occur in balanced ratio across populations. This is a unique characteristic for Upeneus species which usually have either seven or eight dorsal-fin spines, respectively. The best distinction of Upeneus heterospinus n. sp. from all other congeners is reached by combined examination of dorsal-fin spines with several other characters such as barbel colour, presence of a mid-lateral body stripe, pigmentation patterns (partly retained also in preserved fish), gill-raker and pectoral-fin ray numbers, and body-shape variables. The high degree of overall morphological differentation among the three most common species U. caudofasciatus n. sp., U. heterospinus n. sp. and U. margarethae, as revealed by the statistical comparisons, strongly contrasts with a still signficant, but much lower degree of differentiation among populations. The diagnostic characteristics of the margarethae group are updated and the importance to use the results of this taxonomic review in ongoing fisheries-related and ecological research is emphasized. Requirements for future taxonomic research featuring the stunning diversity of the goatfish genus Upeneus are also discussed.publishedVersio

    Instabilité et particularités de l'évolution d'une nappe tourbillonnaire

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    L'instabilité et les particularités de l'évolution d'une nappe tourbillonnaire sont étudiées. Nous considérons l'auto-organisation de tourbillons localisés (dans des écoulements bidimensionnels) en groupements de tourbillons, en structures sous forme de spirale et nous montrons que les états quasi-finaux « n'oublient pas » les conditions initiales. Nous discutons la signification physique des résultats obtenus

    The Atlantic Water boundary current in the Nansen Basin : transport and mechanisms of lateral exchange

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    Author Posting. © American Geophysical Union, 2016. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 121 (2016): 6946–6960, doi:10.1002/2016JC011715.Data from a shipboard hydrographic survey near 30°E in the Nansen Basin of the Arctic Ocean are used to investigate the structure and transport of the Atlantic Water boundary current. Two high-resolution synoptic crossings of the current indicate that it is roughly 30 km wide and weakly middepth-intensified. Using a previously determined definition of Atlantic Water, the transport of this water mass is calculated to be 1.6 ± 0.3 Sv, which is similar to the transport of Atlantic Water in the inner branch of the West Spitsbergen Current. At the time of the survey a small anticyclonic eddy of Atlantic Water was situated just offshore of the boundary current. The data suggest that the feature was recently detached from the boundary current, and, due to compensating effects of temperature and salinity on the thermal wind shear, the maximum swirl speed was situated below the hydrographic property core. Two other similar features were detected within our study domain, suggesting that these eddies are common and represent an effective means of fluxing warm and salty water from the boundary current into the interior. An atmospheric low-pressure system transiting south of our study area resulted in southeasterly winds prior to and during the field measurements. A comparison to hydrographic data from the Pacific Water boundary current in the Canada Basin under similar atmospheric forcing suggests that upwelling was taking place during the survey. This provides a second mechanism related to cross-stream exchange of heat and salt in this region of the Nansen Basin.Arctic Ocean program at the FRAM-High North Research Centre for Climate and the Environment; Steven Grossman Family Foundation; National Science Foundation Grant Number: ARC-12640982017-03-2
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