14,958 research outputs found
Arc Operads and Arc Algebras
Several topological and homological operads based on families of projectively
weighted arcs in bounded surfaces are introduced and studied. The spaces
underlying the basic operad are identified with open subsets of a
compactification due to Penner of a space closely related to Riemann's moduli
space. Algebras over these operads are shown to be Batalin-Vilkovisky algebras,
where the entire BV structure is realized simplicially. Furthermore, our basic
operad contains the cacti operad up to homotopy, and it similarly acts on the
loop space of any topological space. New operad structures on the circle are
classified and combined with the basic operad to produce geometrically natural
extensions of the algebraic structure of BV algebras, which are also computed.Comment: Published by Geometry and Topology at
http://www.maths.warwick.ac.uk/gt/GTVol7/paper15.abs.htm
Feynman Categories
In this paper we give a new foundational, categorical formulation for
operations and relations and objects parameterizing them. This generalizes and
unifies the theory of operads and all their cousins including but not limited
to PROPs, modular operads, twisted (modular) operads, properads, hyperoperads,
their colored versions, as well as algebras over operads and an abundance of
other related structures, such as crossed simplicial groups, the augmented
simplicial category or FI--modules.
The usefulness of this approach is that it allows us to handle all the
classical as well as more esoteric structures under a common framework and we
can treat all the situations simultaneously. Many of the known constructions
simply become Kan extensions.
In this common framework, we also derive universal operations, such as those
underlying Deligne's conjecture, construct Hopf algebras as well as perform
resolutions, (co)bar transforms and Feynman transforms which are related to
master equations. For these applications, we construct the relevant model
category structures. This produces many new examples.Comment: Expanded version. New introduction, new arrangement of text, more
details on several constructions. New figure
Legal Corruption
We challenge the conventional definition of corruption as the abuse of public office for private gain, making a distinction between legal and illegal forms of corruption, and paying more attention to corporate patterns of corruption (which also affect public corruption). We undertake to identify general determinants of the pattern of legal and illegal corruption worldwide, and present a model where both corruption (modeled explicitly in the context of allocations) and the political equilibrium are endogenous. Three types of equilibrium outcomes are identified as a function of basic parameters, namely initial conditions (assets/productivity), equality, and fundamental political accountability. These equilibria are: i) an illegal corruption equilibrium, where the political elite does not face binding incentives; ii) a legal corruption equilibrium, where the political elite is obliged to incur on a cost to deceive the population; and iii) a no-corruption equilibrium, where the population cannot be deceived. An integral empirical test of the model is performed, using a broad range of variables and sources. Its core variables, namely regarding legal corruption (and other manifestations of corporate corruption) come from an original survey developed with the World Economic Forum (in the Executive Opinion Survey 2004 of the Global Competitiveness Report). The empirical results generally validate the model and explanations. Some salient implications emerge.
Testing of pear trees on their own roots in comparison with important used rootstocks under organic farming conditions with special regard to fire blight (E. amylovora)
Pear trees on their own roots are tested in comparison to grafted trees in growth and yield
characteristics and with special regard to the tolerance to diseases, above all fire blight
(Erwinia amylovora). In spring 2004 15 randomized trees of the cultivar 'Williams' from
three variants (self rooted in vitro, self rooted long cuttings, grafted on Quince A) were
planted in a pear orchard, which was heavily infected with fire blight (Erwinia amylovora)
the previous years. The trees were left untreated. Growth and yield characteristics, plant
diseases and tree losses were observed. After four years the in vitro self rooted trees were
significantly more vigorous in growth than those grafted on quince A. The self rooted long
cuttings were comparable in growth with grafts on quince, but showed high tree losses
probably due to frost damages in the first winter one year after planting. However no
infections with Erwinia amylovora could be observed so far. In a field trial with more
cultivars and rootstock variants planted in 2006 at two organically managed sites more
significant effects are expected in the next years
Prickly Pear Cactus and Pastoralism in Southwest Madagascar
Madagascar\u27s Mahafale cattle raisers have adopted several species of the prickly pear cactus (Opuntia) into their subsistence patterns. Their use of Opuntia has had the economic effects of both sedentary and transhumant intensification. It lengthens the stay of pastoralists at their villages and structures the timing of their seasonal migration to distant pastures
09-05 "The Environmental Impacts of Soybean Expansion and Infrastructure Development in Brazil’s Amazon Basin"
For decades, the development of transportation infrastructure in the Brazilian Amazon has been the government’s main social and economic development policy in the region. Reductions in transportation costs have not only opened the agricultural frontier to cattle ranching and logging but have also caused more than two-thirds of Amazonian deforestation. Currently, soybean cultivation is a new economic force demanding improvements to roads in the region. Profitable soybean crops have spread over the Mato Grosso’s cerrados and now head toward the core of the Amazon rain forest. One of the main constraints for soy expansion into the Amazon has been the poor condition of roads. In this study, we analyze the effect Amazon transportation infrastructure programs have on soybean expansion by lowering transport costs. The analysis is based on spatial estimates of transportation costs for the soybean sector, first using current road networks and then projecting changes based on the paving of the Cuiabá-Santarém road. Our results indicate that paving the Cuiabá-Santarém road would reduce transportation costs by an average of 180 million for soybean farmers over a period of twenty years. These benefits, however, ignore the project’s environmental impacts. If the destruction of ecological services and products provided by the existing forests is accounted for, then the Cuiabá-Santarém investment would generate a net loss of between 1.9 billion. This result shows the importance of including the value of the natural capital in feasibility studies of infrastructure projects to reflect their real benefits to society as a whole.
Observations of OJ 287 from the Geodetic VLBI Archive of the Washington Correlator
We present 27 geodetic VLBI maps of OJ 287 obtained from the archive of the
Washington correlator. The observations presented here were made between 1990
October and 1996 December. During this period a sequence of six superluminal
components has been identified. We measured the proper motion of these
components to be approximately 0.5 mas/yr, which is about twice as high as that
seen in previous VLBI observations. These results imply a higher component
ejection rate than previously observed, in good agreement with the observed
occurrences of radio outbursts. We have examined a possible connection between
VLBI components and optical flares in the framework of a binary black hole
system.Comment: 9 pages, 5 included figures, emulateapj.sty, accepted to The
Astrophysical Journa
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