1,720,959 research outputs found
Indications on neutrino oscillation parameters from initial KEK-to-Kamioka and current SK data
No full text
Influence of the magnetic field on the fermion scattering off bubble and kink walls
No full textWe investigate the scattering of fermions off domain walls at the electroweak phase transition in the presence of a magnetic field. We consider both the bubble wall and the kink domain wall. We derive and solve the Dirac equation for fermions with momentum perpendicular to the walls, and compute the transmission and reflection coefficients. In the case of kink domain wall, we briefly discuss the zero mode solutions localized on the wall. The possible role of the magnetic field for the electroweak baryogenesis is also discussed
Solar neutrino event spectra: Tuning SNO to equalize Super-Kamiokande
No full textThe Super-Kamiokande (SK) and the Sudbury Neutrino Observatory (SNO) experiments are monitoring the flux of B-8 solar neutrinos through the elect;on energy spectrum from the reactions nu (e,mu,tau)+ e(-)--> nu (e,mu,tau)+e(-) and nu (e)+d-->p+p+e(-), respectively. We show that the SK detector response to B-8 neutrinos in each bin of the electron energy spectrum (above 8 MeV) can be approximated, with good accuracy, by the SNO detector response in an appropriate electron energy range (above 5.1 MeV). For instance, the SK response in the bin [10, 10.5] MeV is reproduced ("equalized") within similar to2% by the SNO response in the range [7.1, 11.75] MeV. As a consequence, in the presence of active neutrino oscillations, the SK and SNO event rates in the corresponding energy ranges turn out to be linearly related, for any functional form of the oscillation probability. Such equalization is not spoiled by the possible contribution of hep neutrinos (within current phenomenological limits). In perspective, when the SK and the SNO spectra will both be measured with high accuracy, the SK-SNO equalization can be used to determine the absolute B-8 neutrino flux, and to cross-check the (non)observation of spectral deviations in SK and SNO. At present, as an exercise, we use the equalization to "predict" the SNO energy spectrum, on the basis of the current SK data. Finally, we briefly discuss some modifications or limitations of our results in the case of sterile nu oscillations and of relatively large Earth matter effects
Inflation-produced magnetic fields in nonlinear electrodynamics
No full textWe study the generation of primeval magnetic fields during inflation era in nonlinear theories of electrodynamics. Although the intensity of the produced fields strongly depends on characteristics of inflation and on the form of electromagnetic Lagrangian, our results do not exclude the possibility that these fields could be astrophysically interesting
Galaxy cluster number count data constraints on cosmological parameters
No full textWe use data on massive galaxy clusters (M
cluster>8×1014
h
−1
M
⊙ within a comoving radius of R
cluster=1.5h
−1 Mpc) in the redshift range 0.05≲z≲0.83 to place constraints, simultaneously, on the nonrelativistic matter density parameter Ω
m
, on the amplitude of mass fluctuations σ
8, on the index n of the power-law spectrum of the density perturbations, and on the Hubble constant H
0, as well as on the equation-of-state parameters (w
0,w
a
) of a smooth dark energy component.
For the first time, we properly take into account the dependence on redshift and cosmology of the quantities related to cluster physics: the critical density contrast, the growth factor, the mass conversion factor, the virial overdensity, the virial radius and, most importantly, the cluster number count derived from the observational temperature data.
We show that, contrary to previous analyses, cluster data alone prefer low values of the amplitude of mass fluctuations, σ
8≤0.69 (1σ C.L.), and large amounts of nonrelativistic matter, Ω
m
≥0.38 (1σ C.L.), in slight tension with the ΛCDM concordance cosmological model, though the results are compatible with ΛCDM at 2σ. In addition, we derive a σ
8 normalization relation, (2σ C.L.).
Combining cluster data with σ
8-independent baryon acoustic oscillation observations, cosmic microwave background data, Hubble constant measurements, Hubble parameter determination from passively evolving red galaxies, and magnitude–redshift data of type Ia supernovae, we find and , the former in agreement and the latter being slightly lower than the corresponding values in the concordance cosmological model. We also find H_{0} = 69.1^{+1.3}_{-1.5}~\mbox {km}/\mbox {s}/\mbox {Mpc}, the fit to the data being almost independent on n in the adopted range [0.90,1.05].
Concerning the dark energy equation-of-state parameters, we show that the present data on massive clusters weakly constrain (w
0,w
a
) around the values corresponding to a cosmological constant, i.e. (w
0,w
a
)=(−1,0). The global analysis gives and (1σ C.L. errors). Very similar results are found in the case of time-evolving dark energy with a constant equation-of-state parameter w=const (the XCDM parametrization). Finally, we show that the impact of bounds on (w
0,w
a
) is to favor top-down phantom models of evolving dark energy
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
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