1,720,959 research outputs found
{Proper time path integrals for gravitational waves: an~improved wave optics framework}
Full text linkWhen gravitational waves travel from their source to an observer, they interact with matter structures along their path, causing distinct deformations in their waveforms. In this study we introduce a novel theoretical framework for wave optics effects in gravitational lensing, addressing the limitations of existing approaches. We achieve this by incorporating the proper time technique, typically used in field theory studies, into gravitational lensing. This approach allows us to extend the standard formalism beyond the eikonal and paraxial approximations, which are traditionally assumed, and to account for polarization effects, which are typically neglected in the literature. We demonstrate that our method provides a robust generalization of conventional approaches, including them as special cases. Our findings enhance our understanding of gravitational wave propagation, which is crucial for accurately interpreting gravitational wave observations and extracting unbiased information about the lenses from the gravitational wave waveforms
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
Wave-optics limit of the stochastic gravitational wave background
Full text linkThe stochastic gravitational wave background (SGWB) is a rich resource of
cosmological information, encoded both in its source statistics and
anisotropies induced by propagation effects. We provide a theoretical
description of it, without employing theoretical tools which rely on the
geometric optics limit. Our formalism is based on the so-called {\it classical
matter approximation} and it is able to capture wave-optics effects, such as
interference and diffraction. We show that the interaction between the
gravitational waves and the cosmic structures along the line-of-sight produce
observable scalar and vector polarization modes, on top of modulating the
tensorial ones. We build the two point correlation function describing the
statistics of the SGWB, and introduce the intensity and gravitational Stokes
parameters for all its components. In the case of an unpolarized, Gaussian and
statistically homogeneous SGWB, we show that the interaction with matter
modulates its intensity and does not generate a net difference between left-
and right- helicity tensor and vector modes, as expected. We demonstrate that,
in order to produce - and - tensor polarization modes the background
must posses an hexadecapole anisotropy, while a quandrupole anisotropy can
source the vector - and - Stokes parameters.Comment: 30 pages plus technical appendices, 4 figures, 2 table
Cosmological Gravitational Waves in the Wave-Optics Limit
No full textreservedGravitational lensing of waves is an intriguing phenomenon that highlights the complex interaction between the properties of the wave and the geometry
of the lens. The lensing behavior is strongly influenced by the relative length scales: when the wavelength of the wave approaches the Schwarzschild radius
of the lens, wave-like effects such as interference, diffraction, and polarization shifts become prominent. These effects significantly alter the waveforms,
introducing intricate modifications that cannot be explained by classical ray-based methods. In this thesis, we expand upon the latest formalism developed
to account for these wave effects, which is based on the proper-time technique. We investigate the potential of this approach in a cosmological setting, addressing more general scenarios involving multiple lenses and sources, and incorporating the effects of the Universe’s expansion.Gravitational lensing of waves is an intriguing phenomenon that highlights the complex interaction between the properties of the wave and the geometry
of the lens. The lensing behavior is strongly influenced by the relative length scales: when the wavelength of the wave approaches the Schwarzschild radius
of the lens, wave-like effects such as interference, diffraction, and polarization shifts become prominent. These effects significantly alter the waveforms,
introducing intricate modifications that cannot be explained by classical ray-based methods. In this thesis, we expand upon the latest formalism developed
to account for these wave effects, which is based on the proper-time technique. We investigate the potential of this approach in a cosmological setting, addressing more general scenarios involving multiple lenses and sources, and incorporating the effects of the Universe’s expansion
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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