1,720,988 research outputs found
SPHerical: A Python Package For Exploring Alternative Dark Matter Models
Full text linkCold dark matter (CDM) cosmological N-body simulations have proved to be powerful tools for studying the evolution and structure of the universe. These simulations, however, predict certain small-scale structure that disagrees with observation. They are also computationally expensive. Thus, the majority of efforts have focused upon the vanilla CDM model. There are, however, a variety of DM models beyond CDM, such as self-interacting dark matter (SIDM), which has shown promise in resolving some of the aforementioned small-scale structure problems. Our new Python package, SPHerical, which we present in this paper, aims to allow for further exploration of SIDM and other alternative DM models. The package is used to simulate the evolution of isolated spherically symmetric DM halos using a Smoothed Particle Hydrodynamics (SPH) framework and gravothermal fluid model. In this paper, we limit our scope to SIDM and compare SPHerical's results with those of similar simulations
Scattering Amplitude Techniques in Classical Gauge Theories and Gravity
Full text linkIn this thesis we present a study of the computation of classical observables in gauge theories and gravity directly from scattering amplitudes. In particular, we discuss the direct application of modern amplitude techniques in the one, and two-body problems for both, scattering and bounded scenarios, and in both, classical electrodynamics and gravity, with particular emphasis on spin effects in general, and in four spacetime dimensions. Among these observables we have the conservative linear impulse and the radiated waveform in the two-body problem, and the differential cross section for the scattering of waves off classical spinning compact objects.
The implication of classical soft theorems in the computation of classical radiation is also discussed. Furthermore, formal aspects of the double copy for massive spinning matter, and its application in a classical two-body context are considered. Finally, the relation between the minimal coupling gravitational Compton amplitude and the scattering of gravitational waves off the Kerr black hole is presented
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
Structure and Local Properties of Dark Matter Halos
No full textThe structure and local properties of dark matter (DM) are important input variables for both direct and indirect detection experiments. Common assumptions about DM, such as, its particle nature being cold and collisionless–CDM–and its distribution in halos being isothermal and spherical, and well-modeled by an isotopic Maxwell-Boltzmann velocity distribution–the Standard Halo Model (SHM)–prove to be at odds with astrophysical observations. In this thesis I present work towards elucidating two areas of refinement to the above-mentioned assumptions regarding DM: 1) allowing moderate self-interactions between DM particles (SIDM), extending the semi-analytic Jeans modeling technique for SIDM halos to multiple dimensions and including baryons and nonspherical effects to study the resulting change in the DM halo structure; 2) quantifying the departure from the SHM by analyzing hydrodynamical simulations of Milky Way (MW) like halos to characterize the impact on local properties of DM induced by satellite galaxies like the Large Magellanic Cloud (LMC) and their implications for direct detection experiments
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
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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