1,720,976 research outputs found
Towards a perfect QCD gravity dual
No full textMany examples of gravitational duals exist of theories that are highly supersymmetric and conformal in the UV yet have the same massless states as QCD. We discuss such theories with an explicit UV cutoff and propose that, by tuning higher dimension operators at the cutoff by hand, the effects of the extra matter states in the UV may be removed from the IR physics. We explicitly work in the AdS–Schwarzschild description of QCD4 and tune the operator TrF4 by relaxing the near horizon limit to reproduce the lattice 0++ glueball mass results. We find that to reproduce the lattice data, the IR and UV cutoffs lie close to each other and there is essentially no AdS-like period between them. The improved geometry gives a better match to the lattice data for 0?+ glueball masses
Chiral dynamics from AdS space
No full textWe study the low energy dynamics of pions in a gravity dual of chiral symmetry breaking. The string theory construction consists of a probe D7 brane in the Constable-Myers nonsupersymmetric background, which has been shown to describe chiral symmetry breaking in the pattern of QCD. We expand the D7 brane's Dirac-Born-Infeld action for fluctuations that correspond to the Goldstone mode and show that they take the form of a nonlinear chiral Lagrangian. We numerically compute the quark condensate, pion decay constant, and higher order Gasser-Leutwyler coefficients. We find their form is consistent with naive dimensional analysis estimates. We also explore the gauging of the quark's chiral symmetries and the vector meson spectrum. <br/
Chiral phase transitions and quantum critical points of the D3/D7(D5) system with mutually perpendicular E and B fields at finite temperature and density
No full textWe study chiral symmetry restoration with increasing temperature and density in gauge theories subject to mutually perpendicular electric and magnetic fields using holography. We determine the chiral symmetry breaking phase structure of the D3/D7 and D3/D5 systems in the temperature-density-electric field directions. A magnetic field may break the chiral symmetry and an additional electric field induces Ohm and Hall currents as well as restoring the chiral symmetry. At zero temperature the D3/D5 system displays a line of holographic BKT phase transitions in the density-electric field plane, while the D3/D7 system shows a mean-field phase transition. At intermediate temperatures, the transitions in the density-electric field plane are of first order at low density, transforming to second order at critical points as density rises. At high temperature the transition is only ever first order
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
A quantitative study of the relationship between mindset and academic performance in firstyear mathematics courses at the University of Cape Town
Full text linkDespite attempts to decrease university drop-out rates, the graduation rate remains low both internationally and locally. Internationally, up to 40% of students who enter higher education do not graduate; in South Africa, the number is higher at 55%. Several studies have found that growth mindset interventions help improve performance in mathematics and language courses. However, most of these studies are carried out outside of South Africa and on children and adolescents. Very little is known about whether and how the growth mindset theory can help improve performance in first-year university courses in South Africa. In this study, the correlation between mindset and performance in first-year mathematics courses is investigated. First-year science, commerce, and engineering students (N=745) enrolled in four different introductory calculus courses participated in this study. Their mindsets were assessed using a survey questionnaire known as the Mindset Assessment Profile (MAP) tool. The reliability of the Mindset Assessment Profile was assessed using Cronbach's alpha coefficient. This was followed by a comparison of mindset scores of students enrolled in different degree programs. Moreover, the participants' average mindset scores in the current study were compared with international mindset scores. The participants' mathematics grades were collected for different assessments during the academic year. The changes in mathematics grades were compared with the mindset scores to examine the relationship between the two variables. The mathematics grade changes were used instead of the grades themselves; this is because the aim was to measure the improvement in mathematics grades rather than the final grade. In the face of failure, students with a growth mindset are predicted to put more effort and seek feedback to improve their grades in subsequent assessments. On average, the participants of this study were growth mindset oriented according to the Mindset Assessment Profile tool. The MAP was moderately reliable, with Cronbach's alpha coefficients ranging between 0.501 and 0.642. Item-by-item analysis showed that reliability could not be improved by the removal of any item in the Mindset Assessment Profile. There was a significant difference between the mindset scores of commerce students and the mindset scores of science and engineering students. Students enrolled in commerce degree programs scored significantly lower than students enrolled in science and engineering degree programs on the MAP. The University of Cape Town students scored higher than Hong Kong university students on the mindset scale but lower than the students in the US. There was no statistically significant correlation between mindset scores and academic performance in any of the degree programs. The correlations were assessed for (a) all the students, (b) students who failed their first mathematics test, and (c) students who scored 75% and above for their first mathematics test. The findings of this study provide a baseline of mindset scores for a South African university population. The tool for measuring mindset may need to be adapted to be better suited for the population outside of the United States. Furthermore, future research should investigate the effects of a growth mindset intervention on academic performance in mathematics grades at the University of Cape Town
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
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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