1,721,085 research outputs found
AN ANALYSIS OF INTERMEDIATE TRANSVERSE-MOMENTUM PION AND PHOTON PRODUCTION IN PP COLLISIONS THROUGH A QCD RESUMMATION MECHANISM
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New Consistency Equations For Lattice Models
No full textNew consistency equations involving the internal energy and-when possible-the order parameter are proposed for lattice models; these equations are shown to be very efficient in classical examples such as the two- and three-dimensional Ising model. However, their peculiarity is that they can also be applied to models where the order parameter is unknown and, consequently, any mean-field approach is ruled out. Applications to the self-avoiding walk and surface models are shown to be successful
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
Non-Gaussian Fluctuations in Biased Resistor Networks: Size Effects Versus Universal Behavior
Full text linkWe study the distribution of the resistance fluctuations of biased resistor networks in nonequilibrium steady states. The stationary conditions arise from the competition between two stochastic and biased processes of breaking and recovery of the elementary resistors. The fluctuations of the network resistance are calculated by Monte Carlo simulations which are performed
for different values of the applied current, for networks of different size and shape and by considering different levels of intrinsic disorder. The distribution of the resistance fluctuations generally exhibits relevant deviations from Gaussianity, in particular when the current approaches the threshold of electrical breakdown. For two-dimensional systems we have shown that this non-Gaussianity is in general related to finite size effects, thus it vanishes in the thermodynamic limit, with the remarkable exception of highly disordered networks. For these systems, close to the critical point of the conductor-insulator transition, non-Gaussianity persists in the large size limit and it is well described
by the universal Bramwell-Holdsworth-Pinton distribution. In particular, here we analyze the role of the shape of the network on the distribution of the resistance fluctuations. Precisely, we
consider quasi-one-dimensional networks elongated along the direction of the applied current or trasversal to it. A significant anisotropy is found for the properties of the distribution. These results apply to conducting thin films or wires with granular structure stressed by high current densities
Mean Field For Topological Excitations of Z2 Spin and Gauge-models
No full textA mean field approach for the disorder parameters is obtained by applying the duality transformation to a Bethe-Peierls type approximation which involves finite clusters. Applications to Z2 models with global and local symmetries are discribed and systematical improvements are obtained by considering clusters of increasing size. For gauge theories a manifestly gauge-invariant mean field is obtained: the phenomenology of the spontaneous symmetry breaking is reproduced by considering the suitable order parameters and the standard mean field for gauge theories in four dimensions is reinterpreted
Criterion For Distinguishing Between Continuous and Discontinuous Transitions In Spin and Gauge Systems
No full textA conjecture, based on a comparison of different mean-field-like approximations, is proposed for determining the first- or second-order character of phase transitions. The q-state Potts model and several gauge theories [Z2, U(N), SU(N), SO(3)] on a lattice are considered. For Z2 gauge theory, in particular, a critical dimensionality dc=3.66 is predicted, whereas for the Potts model qc=2.75 in d=3, qc=2.4 in d=4, and qc∝exp[1/(d-1)] for d→1 are obtained
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