1,720,962 research outputs found
MULTICANONICAL ALGORITHMS FOR 1ST ORDER PHASE-TRANSITIONS
No full textBERG BA, Neuhaus T. MULTICANONICAL ALGORITHMS FOR 1ST ORDER PHASE-TRANSITIONS. PHYSICS LETTERS B. 1991;267(2):249-253.Monte Carlo simulations are discussed for systems of volume V = L(d) which undergo a first order phase transition in the finite volume limit. Conventional canonical, local Monte Carlo algorithms suffer from exponentially fast slowing down approximately V2 exp(cL(d-1)). Here we present a class of multicanonical Monte Carlo algorithms which can reduce the slowing down to a quadratic power law approximately V2
A DETERMINATION OF INTERFACE-FREE ENERGIES
No full textBILLOIRE A, Neuhaus T, BERG BA. A DETERMINATION OF INTERFACE-FREE ENERGIES. NUCLEAR PHYSICS B. 1994;413(3):795-812.We determine the interface free energy F(o.d.) between disordered and ordered phases in the q = 10 and q = 20 2d Potts models using the results of multicanonical Monte Carlo simulations on L2 lattices, and suitable finite-volume estimators. Our results, when extrapolated to the infinite-volume limit, agree to high precision with recent analytical calculations. At the transition point beta(t) the probability distribution function of the energy exhibits two maxima. Their locations have 1/L2 corrections, in contradiction with claims of 1/L behavior made in the literature. Our data show a flat region in between the two maxima which characterizes two domain configurations
PROPERTIES OF INTERFACES IN THE 2 AND 3-DIMENSIONAL ISING-MODEL
No full textBERG BA, HANSMANN U, Neuhaus T. PROPERTIES OF INTERFACES IN THE 2 AND 3-DIMENSIONAL ISING-MODEL. ZEITSCHRIFT FUR PHYSIK B-CONDENSED MATTER. 1993;90(2):229-239.To investigate order-order interfaces, we perform multimagnetical Monte Carlo simulations of the 2D and 3D Ising model. Following Binder we extract the interfacial free energy from the infinite volume limit of the magnetic probability density. Stringent tests of the numerical methods are performed by reproducing with high precision exact 2D results. In the physically more interesting 3D case we estimate the amplitude F-0(S) of the critical interfacial tension F3 = F-0(S)t(mu) to be F-0(S) = 1.52 +/- 0.05. This result is in good agreement with a previous MC calculation by Mon, as well as with experimental results for related amplitude ratios. In addition, we study in some details the shape of the magnetic probability density for temperatures below the Curie point
SIMULATION OF AN ENSEMBLE WITH VARYING MAGNETIC-FIELD - A NUMERICAL DETERMINATION OF THE ORDER-ORDER INTERFACE TENSION IN THE D=2 ISING-MODEL
No full textBERG BA, HANSMANN U, Neuhaus T. SIMULATION OF AN ENSEMBLE WITH VARYING MAGNETIC-FIELD - A NUMERICAL DETERMINATION OF THE ORDER-ORDER INTERFACE TENSION IN THE D=2 ISING-MODEL. PHYSICAL REVIEW B. 1993;47(1):497-500.In analogy with a recently proposed multicanonical ensemble we introduce an ensemble where the partition function is simulated with a term in the action containing a varying magnetic field. Using this ensemble we demonstrate on lattices with periodic boundary conditions that it is possible to enhance the appearance of order-order interfaces by many orders of magnitude. To perform a stringent test of the method we consider the D = 2 Ising model at beta = 0.5 and simulate square lattices up to size 100 x 100. By a finite-size scaling analysis, the order-order interface tension per unit area is obtained. Our best infinite-volume extrapolation is in excellent agreement with Onsager's exact result
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
MULTICANONICAL ENSEMBLE - A NEW APPROACH TO SIMULATE 1ST-ORDER PHASE-TRANSITIONS
No full textBERG BA, Neuhaus T. MULTICANONICAL ENSEMBLE - A NEW APPROACH TO SIMULATE 1ST-ORDER PHASE-TRANSITIONS. PHYSICAL REVIEW LETTERS. 1992;68(1):9-12.Relying on the recently proposed multicanonical algorithm, we present a numerical simulation of the first-order phase transition in the 2D 10-state Potts model on lattices up to sizes 100 x 100. It is demonstrated that the new algorithm lacks an exponentially fast increase of the tunneling time between metastable states as a function of the linear size L of the system. Instead, the tunneling time diverges approximately proportional to L 2.65. On our largest lattice we gain more than 2 orders of magnitude as compared to a standard heat-bath algorithm. As a first physical application we report a high-precision computation of the interfacial free energy per unit area
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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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