1,720,980 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
Catching Dark Photons in the Sky: Looking for light vector particles using satellites
No full textThe lack of signals in traditional dark matter (DM) searches beyond gravitational interactions provide an excellent reason to investigate weakly coupled and/or light dark sectors (DS). These receive motivation both from the theoretical and the phenomenological side with rich physics across many different scales. Depending on the exact composition of the DS the signals can show up at colliders, in astrophysical searches, and in specialised direct detection experiments, which differ significantly from traditional nuclear recoil searches. Furthermore, the low mass of these new particles opens up new opportunities for producing new physics in the lab beyond the typical high-energy accelerators required for detecting new heavy states. This thesis will focus specifically on a broad class of DSs, namely those containing a Dark Photon (DP) in the particle spectrum. The DP is a well-motivated candidate which can act as a mediator between the standard model (SM) and the DS but it is also known to provide a rich phenomenology by itself. This ranges from the oblique corrections to electroweak precision observables (EWPO) at high DP masses to the subtle impact of a light DP on electromagnetism (EM). This thesis will provide an introduction to the conventional coupling of the DP to the full electroweak theory via the so-called kinetic mixing. We will further discuss potential generalisations of this mixing, i.e. via the Z boson mass or the Stückelberg mechanism. We will show how a light DP decouples from observables at colliders and that the kinetic mixing to electromagnetism is the low-energy theory emerging from the mixing with the hypercharge boson. This mixing with the photon enables non-trivial effects of the DP in an SM plasma. We will use the well-known plasma effects to calculate the solar DP flux emerging from the plasma of solar electrons. In contrast to the majority of the literature, we will focus on the angular distribution of the solar DP flux and point out the advantage of applying this additional information to helioscope searches for DPs. Using data from Hinode XRT, a solar x-ray telescope, we demonstrate that the sensitivity boost can be significant. This observation is interesting in light of future helioscopes, which is briefly discussed in this thesis as well. The second part of this thesis will then be focussing on the dark matter puzzle and the potential role of the DP as a DM candidate. After providing a brief introduction to the topic, we consider the LISA Path nder (LPF) mission as a direct detection experiment for ultralight DPDM. In the spirit of a "no-go theorem", we provide reasons why the direct detection of kinetically mixed DPs using LPF is impossible. This result is also valid for other direct detection setups with only a few caveats. However, we demonstrate that LPF is an interesting instrument for investigating the signal of "general DPs", i.e. DPs gauged under global SM symmetries such as B − L . We point out that the auxiliary channels of LPF provide a powerful tool to look for the DM signal, emphasising why it is expected to be better than the main channel. In addition, potential follow-up projects 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
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
iDM@IDM: Electron recoils from terrestrial upscattering of inelastic dark matter - Electron recoils from terrestrial upscattering
No full textThe growing interest in the interactions between dark matter particles and electrons has received a further boost by the observation of an excess in electron recoil events in the XENON1T experiment. Of particular interest are dark matter models in which the scattering process is inelastic, such that the ground state can upscatter into an excited state. The subsequent exothermic downscattering of such excited states on electrons can lead to observable signals in direct detection experiments and gives a good fit to the XENON1T excess. In this talk, I will discuss terrestrial upscattering, i.e. inelastic scattering of dark matter particles on nuclei in the Earth, as a plausible origin of such excited states. I will demonstrate that both analytical and Monte Carlo methods allow for a detailed prediction of the excited density and velocity distribution. These results show a time dependence of the flux of excited states resulting from the rotation of the Earth. This daily modulation offers an intriguing opportunity to distinguish this mechanism from alternative explanations of the XENON1T excess and to additionally determine the DM mass.This talk will be based on https://arxiv.org/abs/2112.06930
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