1,720,975 research outputs found
Measurement of the electric form factor of the neutron using the reaction 3He(e,e’n)pp up to Q2=3.4 GeV2
No full textSpectral-statistics analysis of the light meson spectrum
No full textQuantum chaos is currently a well established discipline with outreach to many fields of physics. The most important signature of quantum chaos is the statistical analysis of the energy spectrum, which distinguishes between systems with integrable and chaotic classical analogues. The spectral statistical techniques inherited from quantum chaos have been applied to the baryon spectrum revealing its likely chaotic behavior in the low energy regime [1,2]. We present a robust analysis of the spectral fluctuations exhibited by the light meson spectrum. With this analysis we can obtain information about the degree of chaos in the spectrum getting insight on the properties of the underlying interactions. Our analysis unveils that the statistical properties of the light meson spectrum are close, but not exactly equal, to those of chaotic systems [3]. Besides the experimental spectrum, we have analyzed several theoretical spectra [4–7] including the latest lattice QCD calculation [8] finding out that, with the single exception of [5], their statistical properties are close to those of a generic integrable system, and thus incompatible with the experimental result
Spectral-statistics properties of the experimental and theoretical light meson spectra
Full text linkAbstractWe present a robust analysis of the spectral fluctuations exhibited by the light meson spectrum. This analysis provides information about the degree of chaos in light mesons and may be useful to get some insight on the underlying interactions. Our analysis unveils that the statistical properties of the light meson spectrum are close, but not exactly equal, to those of chaotic systems. In addition, we have analyzed several theoretical spectra including the latest lattice QCD calculation. With a single exception, their statistical properties are close to those of a generic integrable system, and thus incompatible with the experimental spectrum
Chaos in hadrons
Full text link6 pags., 5 figs., 1 tab. -- Rutherford Centennial Conference on Nuclear Physics 8–12 August 2011, Manchester, UKIn the last decade quantum chaos has become a well established discipline with outreach to different fields, from condensed-matter to nuclear physics. The most important signature of quantum chaos is the statistical analysis of the energy spectrum, which distinguishes between systems with integrable and chaotic classical analogues. In recent years, spectral statistical techniques inherited from quantum chaos have been applied successfully to the baryon spectrum revealing its likely chaotic behaviour even at the lowest energies. However, the theoretical spectra present a behaviour closer to the statistics of integrable systems which makes theory and experiment statistically incompatible. The usual statement of missing resonances in the experimental spectrum when compared to the theoretical ones cannot account for the discrepancies. In this communication we report an improved analysis of the baryon spectrum, taking into account the low statistics and the error bars associated with each resonance. Our findings give a major support to the previous conclusions. Besides, analogue analyses are performed in the experimental meson spectrum, with comparison to theoretical models.Peer reviewe
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
Unexpected impact of D waves in low-energy neutral pion photoproduction from the proton and the extraction of multipoles
No full textContributions of D waves to physical observables for neutral pion photoproduction from the proton in the near-threshold region are studied and means to isolate them are proposed. Various approaches to describe the multipoles are employed-a phenomenological one, a unitary one, and heavy baryon chiral perturbation theory. The results of these approaches are compared and found to yield essentially the same answers. D waves are seen to enter together with S waves in a way that any means which attempt to obtain the E0+ multipole accurately must rely on knowledge of D waves and that consequently the latter cannot be dismissed in analyses of low-energy pion photoproduction. It is shown that D waves have a significant impact on double-polarization observables that can be measured. This importance of D waves is due to the soft nature of the S wave and is a direct consequence of chiral symmetry and the Nambu-Goldstone nature of the pion. F-wave contributions are shown to be negligible in the near-threshold region.Spain. Ministerio de Ciencia e InnovaciónUnited States. Department of Energy (contract No. DE-FG02-94ER40818
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
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