1,720,961 research outputs found
On the Heart of a faithful torsion theory
No full textIt was shown in [R. Colpi and K. R. Fuller, Trans. Amer. Math. Soc. 359 (2007), no. 2, 741--765 (electronic); MR2255195] that for any ring R and faithful torsion theory (X,Y) on Mod-R there is a cocomplete abelian category H(X,Y), the heart associated to (X,Y), and a tilting object V in H(X,Y) with End(V)≃R and which induces a counterequivalence between the torsion theory, (T,F), generated in H(X,Y) by V and (X,Y).
In this paper it is shown first that if A is any abelian category with a tilting object W such that End(W)≃R and which tilts the torsion theory it generates in A to (X,Y), then A must be equivalent to H(X,Y).
Next, it is shown that if H is an abelian category containing a tilting object V then H must have arbitrary coproducts, indeed must be AB4, and both functors HV=HomA(V,−) and HV′=Ext1A(V,−) from H to Mod-R must commute with coproducts. Furthermore, HV commutes with direct limits iff H is Grothendieck. Also, if (X,Y) is a faithful torsion theory in a module category then H(X,Y) has an injective cogenerator iff (X,Y) is cogenerated by a cotilting module.
Further results include that if (X,Y) is a hereditary cotilting torsion theory then (X,Y) is Grothendieck and that, if (X,Y) is faithful, then H(X,Y) is equivalent to a module category iff it is the heart of the t-structure on Db(Mod-R) generated by a tilting complex (in particular this will be so if X is generated by a tilting module)
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
On the structure of *-modules
No full textLet A and B be rings, A a subcategory of Mod-A closed under submodules and containing AA, and B a subcategory of Mod-B closed under direct sums and epimorphic images. Then any equivalence between A and B is represented by a bimodule APB with A=EndPB via the functors --⊗AP and HomB(P,–). This was proved by Menini and A. Orsatti [Rend. Sem. Mat. Univ. Padova 82 (1989), 203--231 (1990); MR1049594 (91h:16026)], and such a module is called a ∗-module. For instance, every quasi-progenerator and every tilting module is a ∗-module. The purpose of this paper is, in the authors' words, "to measure the gaps between the classes of ∗-modules, of quasi-progenerators and of tilting modules''. Among the results in this direction, it is shown that every finitely generated ∗-module over a commutative ring is a quasi-progenerator; and that this is not the case in general
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Lorentz Breaking Effective Field Theory Models for Matter and Gravity: Theory and Observational Constraints
No full textA number of different approaches to quantum gravity are at least partly phenomenologically characterized by their treatment of Lorentz symmetry, in particular whether the symmetry is exact or modified/broken at the smallest scales. For example, string theory generally preserves Lorentz symmetry while analog gravity and Lifshitz models break it at microscopic scales. In models with broken Lorentz symmetry, there are a vast number of constraints on departures from Lorentz invariance that can be established with low-energy experiments by employing the techniques of effective field theory in both the matter and gravitational sectors. We shall review here the low-energy effective field theory approach to Lorentz breaking in these sectors, and present various constraints provided by available observations
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
- …
