1,721,035 research outputs found
Correlation energy contribution to nuclear masses
No full textDuring the last few years, much effort has been made to develop a microscopic description of the nuclear masses based on mean field theory. The accuracy achieved, when phenomenological parameters are added to take specific effects into account (Wigner term, cut-off in pairing space, etc.), leads to a rms of 0.6–0.7 MeV [S. Goriely, F. Tondeur, J.M. Pearson, Atom Data Nucl. Data Tables 77 (2001) 311] (see also [M. Bender, P.H. Heenen, P.G. Reinhard, Rev. Modern Phys. 75 (2003) 121]). We present evidence that further progress can be made by taking into account medium polarization effects associated with surface and pairing vibrations [S. Baroni, M. Armati, F. Barranco, R.A. Broglia, G. Colò, G. Gori, E. Vigezzi, J. Phys. G: Nucl. Part. Phys. 30 (2004) 1353; S. Baroni, F. Barranco, P.F. Bortignon, R.A. Broglia, G. Colò, E. Vigezzi, Phys. Rev. C 74 (2006) 024305] (see also [M. Bender, G.F. Bertsch, P.-H. Heenen, Phys. Rev. C 73 (2006) 034322])
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
Parity inversion and breakdown of shell closure in Be isotopes
Full text linkThe coupling of single-particle motion and of vibrations in 411Be produces dressed neutrons which spend only a fraction of the time in pure single-particle states, and which weighing differently from the bare neutrons lead to parity inversion. The interaction of the two least bound neutrons in the ground state of 412Be mediated by the v14 Argonne nucleon-nucleon potential and by the exchange of surface vibrations of the core 10Be gives rise to a strongly correlated state, where the two valence neutrons are distributed over s2,p2, and d2 configurations, resulting in the breaking of the N=8 shell closure
Particle-vibration coupling in halo nuclei
No full textIn halo nuclei like 11Li and 12Be, polarization effects based on the particle-vibration coupling mechanism leads to a density dependent pairing interaction which provides most of the observed correlation energy which stabilizes the least two bound neutrons. The same mechanism is at the basis of the parity inversion phenomenon observed in 10Li and 11Be
Microscopic quantal calculation of the vortex-nucleus interaction in the inner crust of neutron stars
No full textIn this article we study the interaction between vortices and nuclei present in the
inner crust of neutron stars, performing microscopic calculations based on quantum mean
field theory. We find that the properties of the vortex are strongly influenced by finite
size effects, leading to qualitative differences respect to results based on semiclassical
approximations
On the structure of vortices in the inner crust of neutron stars
No full textWe study the structure of vortices and their interaction with nuclei in the inner crust of neutron stars. Vortices carry most of the angular momentum of the crust and according to some models are expected to play a key role in the phenomenon of glitches. The quantities of interest (the energy, the pairing gap, the density and the velocity field) are calculated in the framework of the Hartree-Fock-Bogoliubov (HFB) quantum mean field theory. We solve the HFB equations testing four different Skyrme functionals in the particle hole-channel and using a density-dependent contact interaction in the particle-particle channel. We find that the structure of a vortex is strongly affected by the presence of the nucleus, a fact which reflects itself in the density dependence of the pinning energy we calculate
Quantum calculation of vortices in the inner crust of neutron stars
Full text linkThe self-consistent mean-field quantum mechanical solution of a vortex and a nucleus immersed in a sea of free
neutrons, a scenario representative of the inner crust of neutron stars, is presented for the first time. Because of
quantal size effects the phase space for vortices inside the nucleus is essentially zero, so that the vortex core opens
up and surrounds the nucleus. As a consequence, pinned configurations (in which a vortex becomes anchored to
the nucleus) are favored at low and high densities in the inner crust. This result is qualitatively different from that
obtained in all previous models, which predict pinning at intermediate densities
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