1,720,994 research outputs found
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
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
Flavorful BSM from Asymptotic Safety
Full text linkDiese Dissertation beinhaltet aktuelle Anwendungen des auf der Renormierungsgruppe (RG)
basierenden Konzepts der Planckskalensicherheit (PS) in der Modellbildung jenseits des Standardmodells
der Teilchenphysik (SM, BSM). PS bezeichnet dabei ein RG-Laufen aller Kopplungen
bis zum Quantengravitationsregime an der Planckskala ohne Vakuuminstabilitäten und
Landau-Pole. Dazu muss die Metastabilität des SM Higgspotentials behoben werden. Wir gehen
diese Aufgabe in minimalen SM-Erweiterungen mit vektorartigen Fermionen, Singulett-Skalaren
oder beiden, mit oder ohne flavour an. Dazu untersuchen wir die RG-Flüsse dieser Modelle in
höheren Schleifenordnungen sowie die gesamten durch BSM-Massen, -Multiplizitäten, -Ladungen
und -Kopplungen aufgespannten verfügbaren Parameterräume. Dabei enthüllen und charakterisieren
wir mehrere fundamentale RG-Mechanismen für PS, sowie deren Zusammenspiel. Die
Forderung nach PS impliziert dann Bedingungen an die BSM-Parameter. Wir studieren auch
die Beschleunigerphänomenologie unsere Modelle, insbesondere im Hinblick auf die Komplementarität
zwischen phänomenologischen und PS-Bedingungen an Parameter. Danach widmen
wir uns einer komplexeren Klasse von BSM Modellen, nämlich anomaliefreien, flavour-vollen
Z‘-Modellen. Das Z‘-Boson kann flavour-verändernde neutrale Ströme auf Baumgraphenniveau
induzieren, die im SM Schleifen- und Cabibbo-Kobayashi-Maskawa-unterdrückt sind. Daher sind
Z‘--Modelle natürliche Kandidaten um experimentell gemessene Abweichungen einiger flavour-
Observablen von ihrer SM-Vorhersage zu erklären. Insbesondere fokussieren wir uns dabei auf
die anhaltenden Anomalien im Zusammenhang mit b -> s μ+ μ- Übergängen sowie die unerwartet
große CP- und U-Spin-Verletzung in D0 -> K+ K- , π+ π- Zerfällen. Allerdings treten
in Z‘-Modellen typischerweise niederenergetische Landau-Pole auf, durch die die Theorien ihre
Vorhersagekraft verlieren. Wir zeigen, wie in Z‘-Modellen die Anomalien im beauty- und charm-
Sektor jeweils aufgelöst und gleichzeitig Landau-Pole hinter die Planckskala geschoben werden
können. Dadurch ergeben sich präzise Vorhersagen für charakteristische, phänomenologische
Signaturen, die an Beschleunigern gesucht werden können.This thesis comprises recent applications of the renormalization group (RG) based concept of
Planck safety (PS) in beyond the Standard Model of particle physics (SM, BSM) model building.
PS refers to a RG flow of all couplings up to the quantum gravity regime at the Planck scale
without any vacuum instabilities or Landau poles. This requires to cure the metastability of
the SM Higgs potential. We tackle this task in several minimal SM extensions featuring vectorlike
fermions, singlet scalars or both, with or without flavor. We investigate the higher looporder
RG flows of these models, scrutinizing their complete available parameter spaces spanned
by BSM masses, multiplicities, charges and couplings. Thereby, we unveil and characterize
several fundamental mechanisms for PS as well as their interplay. Requiring PS then results
in constraints on BSM parameters. We also study the collider phenomenology of our models,
focusing in particular on the complementarity between phenomenological and PS constraints. We
then turn to a class of more complex BSM models, namely flavorful, anomaly-free Z‘ models. The
Z‘ boson can induce flavor-changing neutral current transitions at tree-level, which in the SM are
loop- and Cabibbo-Kobayashi-Maskawa-suppressed. Therefore, Z‘ models are natural candidates
to address several experimentally measured deviations from the SM in flavor observables. In
particular, we focus on the persistent anomalies in b -> s μ+ μ- transitions as well as the large
CP and U-spin breaking in D0 -> K+ K- , π+ π- decays. On the other hand, Z‘ models are
generically plagued by low-energy Landau poles spoiling the predictivity of the theory. We show
how the flavor anomalies in the beauty and charm sector can respectively be resolved in Z‘
models while the notorious Landau pole is simultaneously pushed beyond the Planck scale. This
results in distinct predictions of characteristic phenomenological signatures that can be searched
for at colliders
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
Constraining light dark vectors and scalar leptoquarks with flavour observables
No full textIn this thesis we explore two complementary extensions of the Standard Model, corresponding to a light new physics scenario featuring a (dark) vector boson, and a heavy new physics scenario involving a scalar leptoquark. Focusing on their flavour-changing interactions and observables, which provide highly sensitive probes of physics beyond the Standard Model, we employ the framework of effective field theory to systematically analyse both setups. In the first part of this thesis, we provide an overview of the Standard Model, flavour and effective field theories. In the second part, we study the light dark vector boson model. We focus on flavour violating interactions between the new vector and the Standard Model fermions, and analyse how such interactions can arise from the Yukawa diagonalisation and the renormalisation group equations at 1-loop. Then, we use experimental data and our theory calculation from two-body decays to set constraints on the model parameters. Furthermore, we also use the tool of perturbative unitarity to set bounds on the model. In the third part, we consider scalar leptoquarks, corresponding to a heavy new physics model. Here, we compute the Wilson coefficients to order for processes from matching the effective and full theories, which involves the calculation of 1-loop amplitudes in the effective theory and 2-loop in the full theory. Finally, we analyse the 1-loop corrections to the effective theory for processes. We focus on a particular computational procedure involving Dirac traces, which requires a careful examination of the Dirac algebra in different schemes, and extract results in a general gauge and for different IR regulators
Baryogenesis originating from lepton number violation induced by right-handed Majorana neutrinos
Full text linkIn this thesis, different ways to use right-handed Majorana neutrinos to explain the active neutrino masses as well as the baryon number asymmetry observed in our universe are investigated. It is shown that the induced lepton number violation can assist baryon number asymmetry generating models, whose asymmetry without additional lepton number violation is completely washed out by sphaleron transitions. Extending this investigation to the scotogenic model, also the relic dark matter abundance observed in our universe can be explained. Furthermore, different mechanisms for generating a lepton number asymmetry directly via interactions involving right-handed Majorana neutrinos are investigated. It is discussed that for models in which the Yukawa couplings of the neutrino sector can be larger than in the type-I seesaw mechanism, the parameter space for thermal leptogenesis is enlarged. Moreover, it is pointed out that considering thermal mass corrections, only an induced mass degeneracy of right-chiral neutrinos enables new prospects of leptogenesis.
Additionally, loop corrections for massive vector bosons interacting with each other are investigated in time-dependent perturbation theory. Studying the case of two interacting massive vector bosons in a simple example in detail, it is shown that the degree of divergence in the S-matrix is the same as expected from R_\xi gauge.In dieser Arbeit werden verschiedene Möglichkeiten untersucht, wie rechtshändige Majorananeutrios zur Erzeugung der beobachteten Baryonzahlasymmetrie beitragen können. Es wird gezeigt, dass die induzierte Leptonenzahlverletzung Baryonenzahlasymmetrie erzeugende Modelle unterstützen kann, bei denen die erzeugte Asymmetrie ohne zusätzliche Leptonenzahlverletzung durch Sphaleronenübergänge wieder ausgelöscht wird. Um zusätzlich die beobachtete Dunkle Materie Dichte zu erklären, wird diese Untersuchung auf das Scotogenic Modell erweitert. Des Weiteren werden verschiedene Mechanismen einer direkten Leptonenzahlasymmetrieerzeugung durch Interaktionen mit rechtshändigen Majorananeutrinos untersucht. Es wird diskutiert, dass sich für Modelle, bei denen größere Yukawakopplungen als im Type-I Seesaw-Mechanismus möglich sind, der Parameterbereich für thermische Leptogenese vergrößern. Außerdem wird gezeigt, dass unter Beachtung thermischer Massenkorrekturen nur eine induzierte Massendegenerierung von rechtschiralen Neutrinos neue Möglichkeiten für Leptogenese eröffnet.
Unabhängig davon werden Schleifenkorrekturen von miteinander wechselwirkenden massiven Vektorbosonen in zeitabhängiger Störungstheorie betrachtet und dabei der Spezialfall von zwei wechselwirkenden massiven Vektorbosonen genauer untersucht. Für ein einfaches Beispiel wird gezeigt, dass der Divergenzgrad der S-Matrix der Erwartung aus der R_\xi-Eichung entspricht
Exploring the interplay between flavor and high-pT observables in the SMEFT framework
No full textDiese Arbeit präsentiert eine globale Analyse zur Suche nach Physik jenseits des Standardmodells im Rahmen der Standardmodell-Effektiven Feldtheorie (SMEFT). Hierzu werden Hochenergie-Daten von Teilchenbeschleunigern mit Präzisionsmessungen aus dem Flavor-Sektor kombiniert, um weitgehend modellunabhängige Schranken auf mögliche neue Wechselwirkungen zu setzen, welche durch Wilson-Koeffizienten parametrisiert sind. Trotz der Erfolge des Standardmodells bei der Beschreibung fundamentaler Wechselwirkungen bleiben zentrale Fragen, wie etwa die Entstehung von Neutrinomassen, die Natur dunkler Materie und die beobachtete Baryonenasymmetrie, unbeantwortet und deuten somit auf die Existenz neuer Physik hin. Angesichts der Herausforderungen direkter Suche nach neuen Teilchen bieten effektive Feldtheorien einen komplementären Ansatz, um diese Phänomene indirekt zu untersuchen. Im Mittelpunkt unserer Analyse stehen die Synergien verschiedener Observablen, die uns erlauben unter Anwendung bayesischer Statistik gleichzeitig Schranken für zahlreiche Wilson-Koeffizienten zu setzen und unbeschränkte Richtungen im Parameterraum aufzulösen. Ein besonderer Schwerpunkt liegt zudem auf der Untersuchung von Flavor-Strukturen. Dazu verwenden wir den Ansatz der Minimalen Flavorverletzung im Quarksektor
sowie lepton-flavorspezifische Szenarien. Unsere Ergebnisse testen Skalen bis zu 1000 TeV, bieten indirekte Informationen über mögliche Flavorstrukturen und eröffnen Perspektiven für zukünftige Forschung.This thesis presents a global analysis aiming to constrain physics beyond the Standard Model within the framework of the Standard Model Effective Field Theory. We combine high-pT collider measurements and precision flavor observables to set largely model-independent bounds on potential new interactions parameterized by the Wilson coefficients. Despite its successes in describing a wide range of processes, the Standard Model of Particle Physics does not account for fundamental phenomena such as neutrino mass generation, dark
matter existence, and baryon asymmetry, thus hinting at the existence of physics beyond the Standard Model. Given the current challenges in the direct detection of new particles, effective field theories offer a complementary approach to probe these phenomena indirectly. Central to our analysis is the systematic exploration of synergies between high-energy collider data and precision flavor observables using a Bayesian statistical framework. A particular emphasis is further placed on the flavor structure, examining the Minimal Flavor Violation approach in the quark sector and lepton-flavor-specific scenarios. Our results probe energy scales up to 1000 TeV, offer indirect insights into potential flavor structures, and outline directions for future research
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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