1,720,981 research outputs found
Tropical Feynman integration in the Minkowski regime
Get PDFWe present a new computer program, feyntrop, which uses the tropical geometric approach to evaluate Feynman integrals numerically. In order to apply this approach in the physical regime, we introduce a new parametric representation of Feynman integrals that implements the causal prescription concretely while retaining projective invariance. feyntrop can efficiently evaluate dimensionally regulated, quasi-finite Feynman integrals, with not too exceptional kinematics in the physical regime, with a relatively large number of propagators and with arbitrarily many kinematic scales. We give a systematic classification of all relevant kinematic regimes, review the necessary mathematical details of the tropical Monte Carlo approach, give fast algorithms to evaluate (deformed) Feynman integrands, describe the usage of feyntrop and discuss many explicit examples of evaluated Feynman integrals
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
Tertiary particle production and target optimization of the H2 beam line in the SPS North Area
No full textH2 beam line of SPS North Area is a high energy, high resolution and multipurpose particle beam line. It is able to transport secondary hadron and pure electron beams with momenta between 10 and 400 GeV/c to be exploited by several different experiments. In this work, tertiary particle production from a secondary target placed in the line is studied. The introduction of this “filter” target enhances the middle to low momentum hadron (20 - 60 GeV/c) and electron production. In this work, a systematic Monte Carlo simulation study using a GEANT 4 based package, G4beamline, has been performed in order to investigate the tertiary particle production from several different targets. More specifically, Cu, W and polyethylene targets with different thicknesses have been studied. The proton over pi+ ratio is of particular interest, as well as the optimal electron production for several momenta. The present work will act as a reference to be used by the future test-beam users of the line as an indication of the expected particle composition and rates in their experimental setups
Anomaly-free Froggatt-Nielsen extensions of the Standard Model with two Higgs doublets
No full textIn this Master thesis we extend the Standard Model with an additional gauge group and an additional Higgs doublet with a lepton specific symmetry. This is used in a gauged version of the Froggatt-Nielsen mechanism to describe the observed masses and mixings among fermions. To reproduce these observables and satisfy the anomaly constraints posed by the new gauge symmetry methods from algebraic geometry are used. By introducing three right-handed neutrinos, an anomaly-free model reproducing the observed masses, PMNS matrix and Cabibbo mixing in the quark sector was found.År 2012 hittade man Higgs boson vid LHC i CERN, den här partikeln är nyckeln för att beskriva hur partiklar får sina massor i standardmodellen. Vad vi fortfarande inte vet, är vilka massor partiklarna får. Detta måste mätas experimentellt och är inte något vi kan teoretiskt förutsäga. Det visar sig att de observerade massorna är vitt skilda, vi har allt från toppkvarkens massa: 172 GeV kg till neutrinerna med en massa mindre än 1 eV kg. För att försöka förklara varför de fundamentala partiklarnas massor är så olika använder vi den så kallade Froggatt-Nielsen mekanismen. Den här mekanismen bygger på att vi introducerar en ny typ av laddning som vi kallar flavonladdning. Precis som elektrisk laddning gör att partiklar växelverkar med fotoner, vilket vi till vardags upplever som elektriska och magnetiska krafter, så gör flavonladdning att partiklarna växelverkar med vad vi kallar ett flavonfält. Om olika partiklar har olika flavonladdning kommer de växelverka olika mycket med flavonfältet. Partiklar med stor flavonladdning växelverkar mycket med flavonfältet och blir därför lättare än partiklar med mindre laddning som växelverkar mindre med fältet. På det här sättet kan vi förklara partiklarnas olika massor med att de har olika flavonladdning. Vi vill inte bara hitta uppsättningar med flavonladdningar som ger de observerade massorna, utan det finns också ett teoretisk villkor som är att teorin måste vara fri från anomalier. Vad det här betyder är att det finns en uppsättning polynomekvationer som laddningarna behöver satisfiera för att modellen ska vara konsistent. I praktiken ser vi till att dessa villkor, tillsammans med de observerade massorna, blir uppfyllda genom att använda metoder från algebraisk geometri. Att hitta laddningsuppsättningar som både är anomalifria och ger de observerade massorna är svårt, vi utökar därför partikelinnehållet i standardmodellen till att innehålla en extra Higgsdublett och högerhänta neutriner. Med dessa tillägg är det möjligt att ha en anomalifri modell som reproducerar alla massor och nästintill all mixning i standardmodellen
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
Analytic and Algebraic Studies of Feynman Integrals
No full textFeynman integrals are central to the calculation of scattering amplitudes both in particle and gravitationalwave physics. This thesis presents advancements in both the analytical and algebraicstructure of these integrals and shows how this can be used for efficient evaluation of these integrals.Paper I. In this paper the focus is on one-loop integrals. The singularities of these integrals arefully described and used to derive the full symbol alphabet and canonical differential equation forany number of external particles. It is proven that a large family of one-loop integrals satisfy theCohen-Macaulay property.Paper II. Two infinite families of Feynman integrals satisfying the Cohen-Macaulay propertyare classified. This property implies that both the singularities and the number of master integralsis independent of space-time dimension and propagator powers.Paper III. In this paper the singular locus of a Feynman integral is defined as the critical pointsof a Whitney stratified map. Explicit code and calculations are provided which show that thismethod captures singularities otherwise hard to detect.Paper IV-V. The algebraic properties of the integrand, especially that of its Newton polytopebeing a generalized permutohedron, is leverage together with tropical sampling to provide efficientnumerical evaluation of Feynman integrals with physical kinematics. The connection betweenthe generalized permutohedron property and the Cohen-Macaulay property is also discussed
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