1,720,971 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Variations on the Author
Get PDF“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
A method of deforming G-structures
No full textWe consider deformations of G-structures via the right action on the frame bundle in a base-point-dependent manner. We investigate which of these deformations again lead to G-structures and in which cases the original and the deformed G-structures define the same instantons. Further, we construct a bijection from connections compatible with the original G-structure to those compatible with the deformed G-structure and investigate the change of intrinsic torsion under the aforementioned deformations. Finally, we consider several examples. (C) 2015 Elsevier B.V. All rights reserved.</p
The -Local Homotopy Theory of Smooth Spaces
Get PDFSimplicial presheaves on cartesian spaces provide a general notion of smooth
spaces. There is a corresponding smooth version of the singular complex
functor, which maps smooth spaces to simplicial sets. We consider the
localisation of the (projective or injective) model category of smooth spaces
at the morphisms which become weak equivalences under the singular complex
functor. We prove that this localisation agrees with a motivic-style
-localisation of the model category of smooth spaces. Further, we
exhibit the singular complex functor for smooth spaces as one of several
Quillen equivalences between model categories for spaces and the above
-local model category of smooth spaces. In the process, we show
that the singular complex functor agrees with the homotopy colimit functor up
to a natural zig-zag of weak equivalences. We provide a functorial fibrant
replacement in the -local model category of smooth spaces and use
this to compute mapping spaces in terms of singular complexes. Finally, we
explain the relation of our fibrant replacement to the concordance sheaf
construction introduced recently by Berwick-Evans, Boavida de Brito and Pavlov.Comment: 44 pages; partially rewritten to improve exposition; proof of Prop.
3.34 in v2 corrected. Published in J. Homotopy Relat. Struc
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
Categorical structures on bundle gerbes and higher geometric prequantisation
Get PDFWe present a construction of a 2-Hilbert space of sections of a bundle gerbe, a suitable
candidate for a prequantum 2-Hilbert space in higher geometric quantisation. We start
by briefly recalling the construction of the 2-category of bundle gerbes, with minor alterations
that allow us to endow morphisms with additive structures. The morphisms in the
resulting 2-categories are investigated in detail. We introduce a direct sum on morphism
categories of bundle gerbes and show that these categories are cartesian monoidal and
abelian. Endomorphisms of the trivial bundle gerbe, or higher functions, carry the structure
of a rig-category, a categorised ring, and we show that generic morphism categories
of bundle gerbes form module categories over this rig-category.
We continue by presenting a categorification of the hermitean bundle metric on a
hermitean line bundle. This is achieved by introducing a functorial dual that extends the
dual of vector bundles to morphisms of bundle gerbes, and constructing a two-variable
adjunction for the aforementioned rig-module category structure on morphism categories.
Its right internal hom is the module action, composed by taking the dual of the acting
higher functions, while the left internal hom is interpreted as a bundle gerbe metric.
Sections of bundle gerbes are defined as morphisms from the trivial bundle gerbe to
the bundle gerbe under consideration. We show that the resulting categories of sections
carry a rig-module structure over the category of nite-dimensional Hilbert spaces with its
canonical direct sum and tensor product. A suitable definition of 2-Hilbert spaces is given,
modifying previous definitions by the use of two-variable adjunctions. We prove that the
category of sections of a bundle gerbe, with its additive and module structures, fits into
this framework, thus obtaining a 2-Hilbert space of sections. In particular, this can be
constructed for prequantum bundle gerbes in problems of higher geometric quantisation.
We define a dimensional reduction functor and show that the categorical structures
introduced on the 2-category of bundle gerbes naturally reduce to their counterparts on
hermitean line bundles with connections. In several places in this thesis, we provide
examples, making 2-Hilbert spaces of sections and dimensional reduction very explicit
Principal -Bundles and Smooth String Group Models
Get PDFWe provide a general, homotopy-theoretic definition of string group models
within an -category of smooth spaces, and we present new smooth models
for the string group. Here, a smooth space is a presheaf of -groupoids
on the category of cartesian spaces. The key to our definition and construction
of smooth string group models is a version of the singular complex functor,
which assigns to a smooth space an underlying ordinary space. We provide new
characterisations of principal -bundles and group extensions in
-topoi, building on work of Nikolaus, Schreiber, and Stevenson. These
insights allow us to transfer the definition of string group extensions from
the -category of spaces to the -category of smooth spaces.
Finally, we consider smooth higher-categorical group extensions that arise as
obstructions to the existence of equivariant structures on gerbes. We show that
these extensions give rise to new smooth models for the string group, as
recently conjectured in joint work with M\"uller and Szabo.Comment: 41 pages, v3: Error in Thm. 3.48 corrected, minor improvements.
Published in Mathematische Annale
Gerbes in Geometry, Field Theory, and Quantisation
Get PDFThis is a mostly self-contained survey article about bundle gerbes and some
of their recent applications in geometry, field theory, and quantisation. We
cover the definition of bundle gerbes with connection and their morphisms, and
explain the classification of bundle gerbes with connection in terms of
differential cohomology. We then survey how the surface holonomy of bundle
gerbes combines with their transgression line bundles to yield a smooth
bordism-type field theory. Finally, we exhibit the use of bundle gerbes in
geometric quantisation of 2-plectic as well as 1- and 2-shifted symplectic
forms. This generalises earlier applications of gerbes to the prequantisation
of quasi-symplectic groupoids.Comment: 38 pages; v2: References added and update
-Bundles
Get PDFHigher bundles are homotopy coherent generalisations of classical fibre
bundles. They appear in numerous contexts in geometry, topology and physics. In
particular, higher principal bundles provide the geometric framework for
higher-group gauge theories with higher-form gauge potentials and their
higher-dimensional holonomies. An -categorical formulation of higher
bundles further allows one to identify these objects in contexts outside the
worlds of smooth manifolds or topological spaces. This article reviews the
theory of -bundles, focussing on principal -bundles, and
surveys several of their applications. It is an invited contribution to the
Topology section in the second edition of the Encyclopedia of Mathematical
Physics.Comment: 24 pages, several diagram
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