1,721,276 research outputs found
Uncovering the mechanism of chiral three-nucleon force in driving spin-orbit splitting
No full textThe three-nucleon force (3NF) is crucial in shaping the shell structure of atomic nuclei, particularly impacting the enhancement of spin-orbit (SO) splitting, especially in nuclei with significant deviations from stability. Despite its importance, the specific mechanisms driving this enhancement remain unclear. In this study, we introduce a decomposition scheme based on the rank of irreducible tensors forming the 3NF, derived from chiral effective field theory at next-to-next-to-leading order, to elucidate their influence on SO splitting. Within the shell-model framework, our analysis reveals that the rank-1 component of the 3NF is the primary factor enlarging the energy gap between the 0p3/2 and 0p1/2 single-particle levels in p-shell nuclei, while the rank-2 component makes a subdominant contribution. Since the rank-1 component originates exclusively from the 2π-exchange 3NF, our finding will not depend on the choice of the low-energy constants of contact terms. We also remark on the antisymmetry of the rank-1 3NF, which can affect the quantum entanglement of spin states. This study lays the groundwork for further exploration into this field toward a microscopic understanding of the 3NF impact on the nuclear shell structure
Mixed Łojasiewicz exponents and log canonical thresholds of ideals
Full text linkWe study the Lojasiewicz exponent and the log canonical threshold of ideals of O-n when restricted to generic subspaces of C-n of different dimensions. We obtain effective formulas of the resulting numbers for ideals with monomial integral closure. An inequality relating these numbers is also proven.The authors thank S. Ishii and T. Krasinski for helpful comments. Part of this work was developed during the stay of the first author at the Max Planck Institute for Mathematics (Bonn, Germany) in April 2011 and the Department of Mathematics of Saitama University (Japan) in March 2012. The first author wishes to thank these institutions for hospitality and financial support.Bivià-Ausina, C.; Fukui, T. (2016). Mixed Lojasiewicz exponents and log canonical thresholds of ideals. Journal of Pure and Applied Algebra. 220(1):223-245. doi:10.1016/j.jpaa.2015.06.007S223245220
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
Wavelength selective photoexcitation of picosecond acoustic-phonon pulses in a triple GaAs/Al<sub>0.3</sub>Ga<sub>0.7</sub>As quantum well structure
No full textUltrashort coherent phonon-pulse generation and detection is investigated in a GaAs–Al0.3Ga0.7As quantum well structure containing three wells of different widths using an optical pump and probe method. The pump photon energy is tuned to the region of the hh1–e1 transition energies of the wells and the probe photon energy is chosen for detection of the phonon pulses that reach the sample surface. By studying the dependence of the probe reflectance change on the pump photon energy, we demonstrate the possibility of wavelength-selective excitation of picosecond acoustic-phonon pulses in quantum wells.<br/
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
Nuclear structure studies within the realistic shell model
No full textThe role of three-nucleon forces on structure properties of nuclei is discussed within the realistic shell model. Calculations are performed by employing effective shell-model Hamiltonians derived by way of many-perturbation theory from chiral potentials including the nucleon-nucleon and three-nucleon components. A sketch of the formalism in treating the three-nucleon force is given and some selected results for f p- and pshell nuclei are shown. Particular attention is devoted to the effects of the three-nucleon force on the monopole component of the effective shell-model interaction by showing how relevant they are in correcting the monopole interaction derived from the nucleon-nucleon force only and correctly describing the formation of shell structure as well as the enhancement in the spin-orbit splitting. A decomposition scheme based on the rank of irreducible tensors forming the three-nucleon force at the next-to-next-to-leading order is also presented to recognize their impact on the spin-orbit enhancement
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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