Search results for "Diagramm"
showing 10 items of 49 documents
Diagrammatic expansion for positive spectral functions beyond GW : Application to vertex corrections in the electron gas
2014
We present a diagrammatic approach to construct self-energy approximations within many-body perturbation theory with positive spectral properties. The method cures the problem of negative spectral functions which arises from a straightforward inclusion of vertex diagrams beyond the GW approximation. Our approach consists of a two-steps procedure: we first express the approximate many-body self-energy as a product of half-diagrams and then identify the minimal number of half-diagrams to add in order to form a perfect square. The resulting self-energy is an unconventional sum of self-energy diagrams in which the internal lines of half a diagram are time-ordered Green's functions whereas those…
Diagrammatic approach to quantum search
2014
We introduce a simple diagrammatic approach for estimating how a randomly walking quantum particle searches on a graph in continuous-time, which involves sketching small weighted graphs with self-loops and considering degenerate perturbation theory's effects on them. Using this method, we give the first example of degenerate perturbation theory solving search on a graph whose evolution occurs in a subspace whose dimension grows with $N$.
Scalar diagrammatic rules for Born amplitudes in QCD
2005
We show that all Born amplitudes in QCD can be calculated from scalar propagators and a set of three- and four-valent vertices. In particular, our approach includes amplitudes with any number of quark pairs. The quarks may be massless or massive. The proof of the formalism is given entirely within quantum field theory.
ViziQuer: A Web-Based Tool for Visual Diagrammatic Queries Over RDF Data
2018
We demonstrate the open source ViziQuer tool for web-based creation and execution of visual diagrammatic queries over RDF/SPARQL data. The tool supports the data instance level and statistics queries, providing visual counterparts for most of SPARQL 1.1 select query constructs, including aggregation and subqueries. A query environment can be created over a user-supplied SPARQL endpoint with known data schema (a data schema exploration service is available, as well). There are pre-defined demonstration query environments for a mini-university data set, a fragment of synthetic similar to reality hospital data set, and a variant of Linked Movie Database RDF data set.
Shall We (Math and) Dance?
2019
Can we use mathematics, and in particular the abstract branch of category theory, to describe some basics of dance, and to highlight structural similarities between music and dance? We first summarize recent studies between mathematics and dance, and between music and categories. Then, we extend this formalism and diagrammatic thinking style to dance.
Cutting rules and positivity in finite temperature many-body theory
2022
Abstract For a given diagrammatic approximation in many-body perturbation theory it is not guaranteed that positive observables, such as the density or the spectral function, retain their positivity. For zero-temperature systems we developed a method [2014 Phys. Rev. B 90 115134] based on so-called cutting rules for Feynman diagrams that enforces these properties diagrammatically, thus solving the problem of negative spectral densities observed for various vertex approximations. In this work we extend this method to systems at finite temperature by formulating the cutting rules in terms of retarded N-point functions, thereby simplifying earlier approaches and simultaneously solving the issu…
Testēšanas modeļa izveide testējamās sistēmas uzlabošanai
2016
Maģistra darba autore, strādājot uzņēmumā “X” par testētāju, novērojusi, ka testējamajā sistēmā “Y” ir tāda funkcionalitātes daļa, kam nav izstrādāti pamata testēšanas scenāriji, kuri balstītos uz darījumprasībām. Šī problēma ir cieši saistīta ar testēšanas pilnības problēmu, jo pilnībā notestēt programmas, kas piešķir vērtības datu objektam, praktiski nav iespējams. Darbā ir analizētas metodes un pieejas, kas var palīdzēt tuvoties testēšanas pilnībai, piedāvājot praktisku pielietojumu vienai no tām – balstītai uz grafisku testēšanas modeli. Šī maģistra darba mērķis bija izpētīt un praktiski pielietot tieši modeļa balstīto testēšanas pieeju, uzņēmuma “X” konkrētai sistēmas “Y” funkcionalitā…
Diagrammatic approach to cellular automata and the emergence of form with inner structure
2018
We present a diagrammatic method to build up sophisticated cellular automata (CAs) as models of complex physical systems. The diagrams complement the mathematical approach to CA modeling, whose details are also presented here, and allow CAs in rule space to be classified according to their hierarchy of layers. Since the method is valid for any discrete operator and only depends on the alphabet size, the resulting conclusions, of general validity, apply to CAs in any dimension or order in time, arbitrary neighborhood ranges and topology. We provide several examples of the method, illustrating how it can be applied to the mathematical modeling of the emergence of order out of disorder. Specif…
Framework for Evaluating the Version Management Capabilities of a Class of UML Modeling Tools from the Viewpoint of Multi-Site, Multi-Partner Product…
2010
UML models are widely used in software product line engineering for activities such as modeling the software product line reference architecture, detailed design, and automation of software code generation and testing. But in high-tech companies, modeling activities are typically distributed across multiple sites and involve multiple partners in different countries, thus complicating model management. Today's UML modeling tools support sophisticated version management for managing parallel and distributed modeling. However, the literature does not provide a comprehensive set of industrial-level criteria to evaluate the version management capabilities of UML tools. This article's contributio…
Representació gràfica i ècfrasi en l’obra de Ramon Llull
2016
El present treball estudia la relació que s’estableix entre text i representacions gràfiques en les obres de Ramon Llull, fent una atenció especial al recurs retòric anomenat ècfrasi, això és, la descripció verbal d’un objecte visual. S’analitzen casos de descripció de figures lul·lianes, sobretot esquemes arboris, en presència de la seva representació (ècfrasi referencial) o en absència de la mateixa (ècfrasi nocional). Es conclou que la dimensió material de les figures i l’assimilació mental del seu funcionament són elements cabdals del procés d’elevació cognitiva que proposa Llull This article discusses the relation established between texts and graphic representations in works of Ramon …