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Quantum field theory of particle oscillations : Neutron-antineutron conversion
Get PDFWe formulate the quantum field theory description of neutron-antineutron oscillations in the framework of canonical quantization, in analogy with the Bardeen-Cooper-Schrieffer theory and the Nambu-Jona-Lasinio model. The physical vacuum of the theory is a condensate of pairs of would-be neutrons and antineutrons in the absence of the baryon-number violating interaction. The quantization procedure defines uniquely the mixing of massive Bogoliubov quasiparticle states that represent the neutron. In spite of not being mass eigenstates, neutron and antineutron states are defined on the physical vacuum and the oscillation formulated in asymptotic states. The exchange of the baryonic number with the vacuum condensate engenders what may be observed as neutron-antineutron oscillation. The convergence between the present canonical approach and the Lagrangian/path integral approach to neutron oscillations is shown by the calculation of the anomalous (baryon-number violating) propagators. The quantization procedure proposed here can be extended to neutrino oscillations and, in general, to any particle oscillations.Peer reviewe
Some Aspects of Quantum Field and Gauge Theories on Noncommutative Space-Time
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Neutrino Oscillations by a Manifestly Coherent Mechanism and Massless vs. Massive Neutrinos
Get PDFThe neutrino oscillations in vacuum are derived in a manifestly coherent
scheme. The mechanism is operative in a quantum field theoretical framework,
justifying nevertheless a formal analogy with quantum mechanical two- (or more)
level systems and their oscillatory behaviour. Both the flavour states and the
massive states are eigenstates of certain Hamiltonians which, in special
conditions, can be argued to share the same Hilbert space. In this scheme,
flavour neutrinos are massless and play the role of asymptotic states for any
interactions, including the weak interactions, while massive neutrinos are
effective propagation states. The vacuum is interpreted as a medium, where the
flavour neutrinos undergo coherent forward scatterings which modify their
energy and mix their flavour. The treatment of matter conversion and MSW effect
fits in naturally; the extension to other neutral particle oscillations, like
, is straightforward. The scheme is eclectic insofar as it
combines seamlessly quantum field theory and quantum mechanics.Comment: 27 page
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
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
Parity of the neutron consistent with neutron-antineutron oscillations
Get PDFIn the analysis of neutron-antineutron oscillations, it has recently been argued in the literature that the use of the i gamma(0) parity n(p)(t, -(x) over right arrow) = i gamma(0)n(t, -(x) over right arrow), which is consistent with the Majorana condition, is mandatory and that the ordinary parity transformation of the neutron field n(p)(t, -(x) over right arrow) = i gamma(0)n(t, -(x) over right arrow) has difficulties. We show that a careful treatment of the ordinary parity transformation of the neutron works in the analysis of neutron-antineutron oscillations. Technically, CP symmetry in a mass diagonalization procedure is important and the two parity transformations i gamma(0)-parity and gamma(0)-parity are compensated for by the PauliGursey transformation. Our analysis shows that either choice of parity gives the correct results for neutronantineutron oscillations if carefully treated.Peer reviewe
Can oscillating neutrino states be formulated universally?
Get PDFA standing problem in neutrino physics is the consistent and universal definition of oscillating neutrino states as coherent superpositions of massive neutrino states. This problem is solved in a quantum field theoretical framework of neutrino mixing developed in analogy with the Nambu-Jona-Lasinio model for the dynamical generation of nucleon masses. The massive neutrino states are Bogoliubov quasiparticles and their vacuum is a condensate of "Cooper pairs" of massless flavour neutrinos. Their superpositions as oscillating neutrino states have intrinsic quantum coherence by construction. In this quantization framework, the standard phenomenological flavour neutrino states and oscillation probability formula are validated in the ultrarelativistic approximation.Peer reviewe
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