1,721,178 research outputs found
Testing the dark matter interpretation of the PAMELA excess through measurements of the galactic diffuse emission
No full textWe propose to test the dark matter (DM) interpretation of the positron excess observed by the PAMELA cosmic-ray (CR) detector through the identification of a Galactic diffuse gamma-ray component associated to DM-induced prompt and radiative emission. The goal is to present an analysis based on minimal sets of assumptions and extrapolations with respect to locally testable or measurable quantities. We discuss the differences between the spatial and spectral features for the DM-induced components (with an extended, possibly spherical, source function) and those for the standard CR contribution (with sources confined within the stellar disc), and propose to focus on intermediate and large latitudes. We address the dependence of the signal to background ratio on the model adopted to describe the propagation of charged CRs in the Galaxy, and find that, in general, the DM-induced signal can be detected by the Fermi Gamma-ray Space Telescope at energies above 100 GeV. An observational result in agreement with the prediction from standard CR components only, would imply very strong constraints on the DM interpretation of the PAMELA excess. On the other hand, if an excess in the diffuse emission above 100 GeV is identified, the angular profile for such emission would allow for a clean disentanglement between the DM interpretation and astrophysical explanations proposed for the PAMELA excess. We also compare to the radiative diffuse emission at lower frequencies, sketching, in particular, the detection prospects at infrared frequencies with the Planck satellite
Multi-wavelength signals of dark matter annihilations at the Galactic center
No full textWe perform a systematic study of the multi-wavelength signal induced by weakly interacting massive particle (WIMP) annihilations at the Galactic Center (GC). Referring to a generic WIMP dark matter (DM) scenario and depending on astrophysical inputs, we discuss spectral and angular features and sketch correlations among signals in the different energy bands. None of the components which have been associated to the GC source Sgr A*, nor the diffuse emission components from the GC region, have spectral or angular features typical of a DM source. Still, data-sets at all energy bands, namely, the radio, near infrared, X-ray and gamma-ray bands, contribute to place significant constraints on the WIMP parameter space. In general, the gamma-ray energy range is not the one with the largest signal to background ratio. In the case of large magnetic fields close to the GC, X-ray data give the tightest bounds. The emission in the radio-band, which is less model dependent, is very constraining as well. The recent detection by HESS of a GC gamma-ray source, and of a diffuse gamma-ray component, limits the possibility of a DM discovery with next generation of gamma-ray telescopes, like GLAST and CTA. We find that the most of the region in the parameter space accessible to these instruments is actually already excluded at other wave-lenghts. On the other hand, there may be still an open window to improve constraints with wide-field radio observations
A dark matter candidate from an extra (non-universal) dimension
Full text linkWe show that a recently constructed five-dimensional (5D) model with gauge-Higgs unification and explicit Lorentz symmetry breaking in the bulk, provides a natural dark matter candidate. This is the lightest Kaluza-Klein particle odd under a certain discrete Z(2) symmetry, which has been introduced to improve the naturalness of the model, and resembles KK-parity but is less constraining.
The dark matter candidate is the first KK mode of a 5D gauge field and electroweak bounds force its mass above the TeV scale. Its pair annihilation rate is too small to guarantee the correct relic abundance; however coannihilations with colored particles greatly enhance the effective annihilation rate, leading to realistic relic densities
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
Meet Met Net - Awareness and design in hyper-technology era
No full textThe complex relationship between man and technology is the starting point of an interesting design process aiming to highlight the lack of awareness in most of the behavioral choices of man. The man is distinguished by its nature of finding short-term solutions, with the almost complete inability of prefiguring repercussions resulting from his unconscious decisions. The technology, on the other hand is growing and developing fast, becoming day by day more autonomous and uncontrollable.
Specific attention is deserved by those technological innovations that can cause unpredicted impacts on human, his principles, values and behaviors: knowing history by its sociological and behavioral implications allows us to recognize some recursive patterns that can then be transformed into opportunities.
The goal is not an attempt to predict future trends in technological innovation but to find the right formula in order to raise the level of responsibility in individuals' behavior. Not by imposing rules but giving people the right awareness in order to make conscious choices and to guarantee a responsible behavior.
The role of the designer and the fields where he can intervene are identified and an area of interest is delimited specifically to the ambit of the 3D printing, enhancing its potential property of changing both technological and human systems. A first answer to the problems triggered by 3D printing can be found, indeed, in the positive phenomena that are activated within collaborating groups by sharing space and knowledge in communities with a bottom-up approach. The designer is actively involved within the entire system, directing behaviors toward the correct ethical and moral responsibility. Therefore, 3D printing does not turn into another behavioral, social, economic and environmental failure
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
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