1,720,958 research outputs found
Machine learning toric duality in brane tilings
No full textWe apply a variety of machine learning methods to the study of Seiberg duality within 4d \mathcal{N}=1 quantum field theories arising on the worldvolumes of D3-branes probing toric Calabi-Yau 3-folds. Such theories admit an elegant description in terms of bipartite tessellations of the torus known as brane tilings or dimer models. An intricate network of infrared dualities interconnects the space of such theories and partitions it into universality classes, the prediction and classification of which is a problem that naturally lends itself to a machine learning investigation. In this paper, we address a preliminary set of such enquiries. We begin by training a fully connected neural network to identify classes of Seiberg dual theories realised on \mathbb{Z}_m\times\mathbb{Z}_n orbifolds of the conifold and achieve R^2=0.988. Then, we evaluate various notions of robustness of our methods against perturbations of the space of theories under investigation, and discuss these results in terms of the nature of the neural network's learning. Finally, we employ a more sophisticated residual architecture to classify the toric phase space of the Y^{6,0} theories, and to predict the individual gauged linear \sigma-model multiplicities in toric diagrams thereof. In spite of the non-trivial nature of this task, we achieve remarkably accurate results; namely, upon fixing a choice of Kasteleyn matrix representative, the regressor achieves a mean absolute error of 0.021. We also discuss how the performance is affected by relaxing these assumptions
Path integral Monte Carlo method for option pricing
No full textThe Markov chain Monte Carlo (MCMC) method, in conjunction with the Metropolis–Hastings algorithm, is used to simulate the path integral for the Black–Scholes–Merton model of option pricing. After a brief derivation of the path integral solution of this model, we develop the MCMC method by discretizing the path integral on a time lattice and evaluating this discretized form for various scenarios. Particular attention is paid to the existence of autocorrelations, their decay with the number of sweeps, and the resulting estimate of the corresponding errors. After testing our approach against closed-form solutions, we demonstrate the utility and flexibility of our method with applications to non-Gaussian models
Holographic Weyl anomalies for 4d defects in 6d SCFTs
No full textIn this note, we study 1/4- and 1/2-BPS co-dimension two superconformal defects in the 6d N=(2,0) AN−1 SCFT at large N using their holographic descriptions as solutions of 11d supergravity. In this regime, we are able to compute the defect contribution to the sphere entanglement entropy and the change in the stress-energy tensor one-point function due to the presence of the defect using holography. From these quantities, we are then able to unambiguously compute the values for two of the twenty-nine total Weyl anomaly coefficients that characterize 4d conformal defects in six and higher dimensions. We are able to demonstrate the consistency of the supergravity description of the defect theories with the average null energy condition on the field theory side. For each class of defects that we consider, we also show that the A-type Weyl anomaly coefficient is non-negative
From large to small N = (4, 4) superconformal surface defects in holographic 6d SCFTs
No full textTwo-dimensional (2d) N = (4, 4) Lie superalgebras can be either ''small'' or ''large'', meaning their R-symmetry is either 𝔰𝔬(4) or 𝔰𝔬(4)⊕𝔰𝔬(4), respectively. Both cases admit a superconformal extension and fit into the one-parameter family 𝔡(2,1;γ)⊕𝔡(2,1;γ), with parameter γ∈(−∞,∞). The large algebra corresponds to generic values of γ, while the small case corresponds to a degeneration limit with γ→−∞. In 11d supergravity, we study known solutions with superisometry algebra 𝔡(2,1;γ)⊕𝔡(2,1;γ) that are asymptotically locally AdS_7 × S^4. These solutions are holographically dual to the 6d maximally superconformal field theory with 2d superconformal defects invariant under 𝔡(2,1;γ)⊕𝔡(2,1;γ). We show that a limit of these solutions, in which γ→−∞, reproduces another known class of solutions, holographically dual to small N = (4, 4) superconformal defects. We then use this limit to generate new small N = (4, 4) solutions with finite Ricci scalar, in contrast to the known small N = (4, 4) solutions. We then use holography to compute the entanglement entropy of a spherical region centered on these small N = (4, 4) defects, which provides a linear combination of defect Weyl anomaly coefficients that characterizes the number of defect-localized degrees of freedom. We also comment on the generalization of our results to include N = (0, 4) surface defects through orbifolding
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
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
- …
