16,048 research outputs found
Grothendieck categories as a bilocalization of linear sites
We prove that the 2-category Grt of Grothendieck abelian categories with
colimit preserving functors and natural transformations is a bicategory of
fractions in the sense of Pronk of the 2-category Site of linear sites with
continuous morphisms of sites and natural transformations. This result can
potentially be used to make the tensor product of Grothendieck categories from
earlier work by Lowen, Shoikhet and the author into a bi-monoidal structure on
Grt
Gabriel-Ulmer duality for topoi and its relation with site presentations
Let be a regular cardinal. We study Gabriel-Ulmer duality when one
restricts the 2-category of locally -presentable categories with
-accessible right adjoints to its locally full sub-2-category of
-presentable Grothendieck topoi with geometric -accessible
morphisms. In particular, we provide a full understanding of the locally full
sub-2-category of the 2-category of -small cocomplete categories with
-colimit preserving functors arising as the corresponding 2-category of
presentations via the restriction. We analyse the relation of these
presentations of Grothendieck topoi with site presentations and we show that
the 2-category of locally -presentable Grothendieck topoi with
geometric -accessible morphisms is a reflective sub-bicategory of the
full sub-2-category of the 2-category of sites with morphisms of sites
genearated by the weakly -ary sites in the sense of Shulman [37].Comment: 25 page
On the tensor product of linear sites and Grothendieck categories
We define a tensor product of linear sites, and a resulting tensor product of
Grothendieck categories based upon their representations as categories of
linear sheaves. We show that our tensor product is a special case of the tensor
product of locally presentable linear categories, and that the tensor product
of locally coherent Grothendieck categories is locally coherent if and only if
the Deligne tensor product of their abelian categories of finitely presented
objects exists. We describe the tensor product of non-commutative projective
schemes in terms of Z-algebras, and show that for projective schemes our tensor
product corresponds to the usual product scheme.Comment: New sections 5.3 on the alpha-Deligne tensor product and 5.4 on
future prospect
Company-university collaboration in applying gamification to learning about insurance
Incorporating gamification into training–learning at universities is hampered by a shortage of quality, adapted educational video games. Large companies are leading in the creation of educational video games for their internal training or to enhance their public image and universities can benefit from collaborating. The aim of this research is to evaluate, both objectively and subjectively, the potential of the simulation game BugaMAP (developed by the MAPFRE Foundation) for university teaching about insurance. To this end, we have assessed both the game itself and the experience of using the game as perceived by 142 economics students from various degree plans and courses at the University of Seville during the 2017–2018 academic year. As a methodology, a checklist of gamification components is used for the objective evaluation, and an opinion questionnaire on the game experience is used for the subjective evaluation. Among the results several findings stand out. One is the high satisfaction of the students with the knowledge acquired using fun and social interaction. Another is that the role of the university professors and the company monitors turns out to be very active and necessary during the game-learning sessions. Finally, in addition to the benefits to the university of occasionally available quality games to accelerate student skills training, the company–university collaboration serves as a trial and refinement of innovative tools for game-based learning
Axially Symmetric Post-Newtonian Stellar Systems
We introduce a method to obtain self-consistent, axially symmetric, thin
disklike stellar models in the first post-Newtonian (1PN) approximation. The
models obtained are fully analytical and corresponds to the post-Newtonian
generalizations of classical ones. By introducing in the field equations
provided by the 1PN approximation a known distribution function (DF)
corresponding to a Newtonian model, two fundamental equations determining the
1PN corrections are obtained, which are solved using the Hunter method. The
rotation curves of the 1PN-corrected models differs from the classical ones
and, for the generalized Kalnajs discs, the 1PN corrections are clearly
appreciable with values of the mass and radius of a typical galaxy. On the
other hand, the relativistic mass correction can be ignored for all models.Comment: 13 pages, 4 figures, to be published at Rev.Integr.Temas Ma
Distribution functions for a family of axially symmetric galaxy models
We present the derivation of distribution functions for the first four
members of a family of disks, previously obtained in (MNRAS, 371, 1873, 2006),
which represent a family of axially symmetric galaxy models with finite radius
and well behaved surface mass density. In order to do this we employ several
approaches that have been developed starting from the potential-density pair
and, essentially using the method introduced by Kalnajs (Ap. J., 205, 751,
1976) we obtain some distribution functions that depend on the Jacobi integral.
Now, as this method demands that the mass density can be properly expressed as
a function of the gravitational potential, we can do this only for the first
four discs of the family. We also find another kind of distribution functions
by starting with the even part of the previous distribution functions and using
the maximum entropy principle in order to find the odd part and so a new
distribution function, as it was pointed out by Dejonghe (Phys. Rep., 133, 217,
1986). The result is a wide variety of equilibrium states corresponding to
several self-consistent finite flat galaxy models.Comment: 12 pages, 7 figures, updated version, accepted for publication in
Rev. Acad. Colomb. Cienc. Ex. Fis. Na
A Comparison of Machine-Learning Methods to Select Socioeconomic Indicators in Cultural Landscapes
Cultural landscapes are regarded to be complex socioecological systems that originated as a result of the interaction between humanity and nature across time. Cultural landscapes present complex-system properties, including nonlinear dynamics among their components. There is a close relationship between socioeconomy and landscape in cultural landscapes, so that changes in the socioeconomic dynamic have an effect on the structure and functionality of the landscape. Several numerical analyses have been carried out to study this relationship, with linear regression models being widely used. However, cultural landscapes comprise a considerable amount of elements and processes, whose interactions might not be properly captured by a linear model. In recent years, machine-learning techniques have increasingly been applied to the field of ecology to solve regression tasks. These techniques provide sound methods and algorithms for dealing with complex systems under uncertainty. The term ‘machine learning’ includes a wide variety of methods to learn models from data. In this paper, we study the relationship between socioeconomy and cultural landscape (in Andalusia, Spain) at two different spatial scales aiming at comparing different regression models from a predictive-accuracy point of view, including model trees and neural or Bayesian networks
Rescissió per lesió del violari o pensió vitalÃcia sobre béns immobles: la consolidació d'una lÃnia jurisprudencial del Tribunal Superior de JustÃcia de Catalunya
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