1,720,963 research outputs found
Theory of interacting vector dark energy and fluid
Full text linkIn this work, we study interaction between dark energy and dark matter, where dark energy is described by a massive vector field, and dark matter is modelled as a fluid. We present a new interaction term, which affects only perturbations and can give interesting phenomenology. Then we present a general Lagrangian for the interacting vector dark energy with dark matter. For the dark energy, we choose Proca theory with term to study its phenomenological consequence. For this model, we explore both background and perturbation dynamics. We also present the no-ghost condition for tensor modes, vector modes and scalar modes. Subsequently, we also study the evolution of the overdensities of both baryon and cold dark matter in the high limit. We show that the effective gravitational coupling is modified for cold dark matter and baryon. We also choose a simple concrete model and numerically show a suppression of the effective gravitational coupling for cold dark matter. However, in this simple model, the suppression of the effective gravitational coupling does not result in a suppression of the matter overdensity compared to that in the CDM model due to the modified background expansion.29 pages, 6 figures, revtex, accepted versio
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
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
Static, spherically symmetric objects in Type-II minimally modified gravity
Full text linkStatic, spherically symmetric solutions representing stars made of barotropic
perfect fluid are studied in the context of two theories of type-II minimally
modified gravity, VCDM and VCCDM. Both of these theories share the property
that no additional degree of freedom is introduced in the gravity sector, and
propagate only two gravitational waves besides matter fields, as in General
Relativity (GR). We find that, on imposing physical boundary conditions on the
Misner-Sharp mass of the system, the solutions in V(C)CDM exactly coincide with
the ones in GR, namely they also satisfy the Tolman-Oppenheimer-Volkoff
equation.Comment: 11 pages, no figures, uses revte
Extended minimal theories of massive gravity
Full text linkIn this work, we introduce a class of extended Minimal Theories of Massive
Gravity (eMTMG), without requiring a priori that the theory should admit the
same homogeneous and isotropic cosmological solutions as the de
Rham-Gabadadze-Tolley massive gravity. The theory is constructed as to have
only two degrees of freedom in the gravity sector. In order to perform this
step we first introduce a precursor theory endowed with a general graviton mass
term, to which, at the level of the Hamiltonian, we add two extra constraints
as to remove the unwanted degrees of freedom, which otherwise would typically
lead to ghosts and/or instabilities. On analyzing the number of independent
constraints and the properties of tensor mode perturbations, we see that the
gravitational waves are the only propagating gravitational degrees of freedom
which do acquire a non-trivial mass, as expected. In order to understand how
the effective gravitational force works for this theory we then investigate
cosmological scalar perturbations in the presence of a pressureless fluid. We
then restrict the whole class of models by imposing the following conditions at
all times: 1) it is possible to define an effective gravitational constant,
; 2) the value is always finite but not
always equal to unity (as to allow some non-trivial modifications of gravity,
besides the massive tensorial modes); and 3) the square of mass of the graviton
is always positive. These constraints automatically make also the ISW-effect
contributions finite at all times. Finally we focus on a simple subclass of
such theories, and show they already can give a rich and interesting
phenomenology.Comment: 20 pages+appendices, 1 figur
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
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