TY - JOUR A1 - Kourou, Maria A1 - Zarvalis, Konstantinos T1 - Compact sets in petals and their backward orbits under semigroups of holomorphic functions JF - Potential Analysis N2 - Let (ϕ\(_t\))\(_{t≥0}\) be a semigroup of holomorphic functions in the unit disk \(\mathbb {D}\) and K a compact subset of \(\mathbb {D}\). We investigate the conditions under which the backward orbit of K under the semigroup exists. Subsequently, the geometric characteristics, as well as, potential theoretic quantities for the backward orbit of K are examined. More specifically, results are obtained concerning the asymptotic behavior of its hyperbolic area and diameter, the harmonic measure and the capacity of the condenser that K forms with the unit disk. KW - semigroup of holomorphic functions KW - backward orbit KW - petal KW - harmonic measure KW - condenser capacity KW - Koenigs function KW - green energy KW - hyperbolic area Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-324368 SN - 0926-2601 VL - 59 IS - 4 ER - TY - JOUR A1 - Fall, Mouhammed Moustapha A1 - Minlend, Ignace Aristide A1 - Ratzkin, Jesse T1 - Foliation of an Asymptotically Flat End by Critical Capacitors JF - The Journal of Geometric Analysis N2 - We construct a foliation of an asymptotically flat end of a Riemannian manifold by hypersurfaces which are critical points of a natural functional arising in potential theory. These hypersurfaces are perturbations of large coordinate spheres, and they admit solutions of a certain over-determined boundary value problem involving the Laplace–Beltrami operator. In a key step we must invert the Dirichlet-to-Neumann operator, highlighting the nonlocal nature of our problem. KW - asymptotically flat ends KW - foliation KW - over-determined problem Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-269997 SN - 1559-002X VL - 32 IS - 2 ER - TY - JOUR A1 - Easton, Andrew A1 - van Dalen, Okki A1 - Goeb, Rainer A1 - Di Bucchianico, Alessandro T1 - Bivariate copula monitoring JF - Quality and Reliability Engineering International N2 - The assumption of multivariate normality underlying the Hotelling T\(^{2}\) chart is often violated for process data. The multivariate dependency structure can be separated from marginals with the help of copula theory, which permits to model association structures beyond the covariance matrix. Copula‐based estimation and testing routines have reached maturity regarding a variety of practical applications. We have constructed a rich design matrix for the comparison of the Hotelling T\(^{2}\) chart with the copula test by Verdier and the copula test by Vuong, which allows for weighting the observations adaptively. Based on the design matrix, we have conducted a large and computationally intensive simulation study. The results show that the copula test by Verdier performs better than Hotelling T\(^{2}\) in a large variety of out‐of‐control cases, whereas the weighted Vuong scheme often fails to provide an improvement. KW - copula KW - multivariate Gaussian distribution KW - multivariate statistical process control (SPC) KW - phase I KW - phase II Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-276501 VL - 38 IS - 3 SP - 1272 EP - 1288 ER - TY - JOUR A1 - Campana, Francesca Calà A1 - Borzì, Alfio T1 - On the SQH Method for Solving Differential Nash Games JF - Journal of Dynamical and Control Systems N2 - A sequentialquadratic Hamiltonian schemefor solving open-loop differential Nash games is proposed and investigated. This method is formulated in the framework of the Pontryagin maximum principle and represents an efficient and robust extension of the successive approximations strategy for solving optimal control problems. Theoretical results are presented that prove the well-posedness of the proposed scheme, and results of numerical experiments are reported that successfully validate its computational performance. KW - successive approximations strategy KW - sequential quadratic hamiltonian method KW - differential nash games KW - pontryagin maximum principle Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-269111 SN - 1573-8698 VL - 28 ER - TY - JOUR A1 - Kraus, Daniela A1 - Moucha, Annika A1 - Roth, Oliver T1 - A sharp Bernstein–type inequality and application to the Carleson embedding theorem with matrix weights JF - Analysis and Mathematical Physics N2 - We prove a sharp Bernstein-type inequality for complex polynomials which are positive and satisfy a polynomial growth condition on the positive real axis. This leads to an improved upper estimate in the recent work of Culiuc and Treil (Int. Math. Res. Not. 2019: 3301–3312, 2019) on the weighted martingale Carleson embedding theorem with matrix weights. In the scalar case this new upper bound is optimal. KW - Bernstein-type inequality KW - complex polynomials KW - Carleson embedding theorem Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-270485 SN - 1664-235X VL - 12 IS - 1 ER - TY - JOUR A1 - Just, Janina A1 - Siller, Hans-Stefan T1 - The role of mathematics in STEM secondary classrooms: a systematic literature review JF - Education Sciences N2 - Nowadays, science, technology, engineering, and mathematics (STEM) play a critical role in a nation’s global competitiveness and prosperity. Thus, there is a need to educate students in these subjects to meet the current and future demands of personal life and society. While applications, especially in science, engineering, and technology, are directly obvious, mathematics underpins the other STEM disciplines. It is recognized that mathematics is the foundation for all other STEM disciplines; the role of mathematics in classrooms is not clear yet. Therefore, the question arises: What is the current role of mathematics in secondary STEM classrooms? To answer this question, we conducted a systematic literature review based on three publication databases (Web of Science, ERIC, and EBSCO Teacher Referral Center). This literature review paper is intended to contribute to the current state of the role of mathematics in STEM education in secondary classrooms. Through the search, starting with 1910 documents, only 14 eligible documents were found. In these, mathematics is often seen as a minor matter and a means to an end in the eyes of science educators. From this, we conclude that the role of mathematics in the STEM classroom should be further strengthened. Overall, the paper highlights a major research gap, and proposes possible initial solutions to close it. KW - STEM education KW - role of mathematics in STEM KW - literature review KW - STEM integration KW - STEM classroom KW - secondary education Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-288075 SN - 2227-7102 VL - 12 IS - 9 ER - TY - JOUR A1 - Dippell, Marvin A1 - Esposito, Chiara A1 - Waldmann, Stefan T1 - Deformation and Hochschild cohomology of coisotropic algebras JF - Annali di Matematica Pura ed Applicata N2 - Coisotropic algebras consist of triples of algebras for which a reduction can be defined and unify in a very algebraic fashion coisotropic reduction in several settings. In this paper, we study the theory of (formal) deformation of coisotropic algebras showing that deformations are governed by suitable coisotropic DGLAs. We define a deformation functor and prove that it commutes with reduction. Finally, we study the obstructions to existence and uniqueness of coisotropic algebras and present some geometric examples. KW - deformation theory KW - differential graded Lie algebra KW - coisotropic reduction Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-329069 VL - 201 IS - 3 ER - TY - JOUR A1 - Greefrath, Gilbert A1 - Siller, Hans-Stefan A1 - Klock, Heiner A1 - Wess, Raphael T1 - Pre-service secondary teachers’ pedagogical content knowledge for the teaching of mathematical modelling JF - Educational Studies in Mathematics N2 - The article deals with the pedagogical content knowledge of mathematical modelling as part of the professional competence of pre-service teachers. With the help of a test developed for this purpose from a conceptual model, we examine whether this pedagogical content knowledge can be promoted in its different facets—especially knowledge about modelling tasks and about interventions—by suitable university seminars. For this purpose, the test was administered to three groups in a seminar for the teaching of mathematical modelling: (1) to those respondents who created their own modelling tasks for use with students, (2) to those trained to intervene in mathematical modelling processes, and (3) participating students who are not required to address mathematical modelling. The findings of the study—based on variance analysis—indicate that certain facets (knowledge of modelling tasks, modelling processes, and interventions) have increased significantly in both experimental groups but to varying degrees. By contrast, pre-service teachers in the control group demonstrated no significant change to their level of pedagogical content knowledge. KW - mathematical modelling KW - pedagogical content knowledge KW - professional competence KW - pre-service teacher Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-308259 SN - 0013-1954 SN - 1573-0816 VL - 109 IS - 2 ER - TY - THES A1 - Kortum, Joshua T1 - Global Existence and Uniqueness Results for Nematic Liquid Crystal and Magnetoviscoelastic Flows T1 - Globale Existenz- und Eindeutigkeitsresultate für nematische Flüssigkristall- und magnetoviskoelastische Flüsse N2 - Liquid crystals and polymeric fluids are found in many technical applications with liquid crystal displays probably being the most prominent one. Ferromagnetic materials are well established in industrial and everyday use, e.g. as magnets in generators, transformers and hard drive disks. Among ferromagnetic materials, we find a subclass which undergoes deformations if an external magnetic field is applied. This effect is exploited in actuators, magnetoelastic sensors, and new fluid materials have been produced which retain their induced magnetization during the flow. A central issue consists of a proper modelling for those materials. Several models exist regarding liquid crystals and liquid crystal flows, but up to now, none of them has provided a full insight into all observed effects. On materials encompassing magnetic, elastic and perhaps even fluid dynamic effects, the mathematical literature seems sparse in terms of models. To some extent, one can unify the modeling of nematic liquid crystals and magnetoviscoelastic materials employing a so-called energetic variational approach. Using the least action principle from theoretical physics, the actual task reduces to finding appropriate energies describing the observed behavior. The procedure leads to systems of evolutionary partial differential equations, which are analyzed in this work. From the mathematical point of view, fundamental questions on existence, uniqueness and stability of solutions remain unsolved. Concerning the Ericksen-Leslie system modelling nematic liquid crystal flows, an approximation to this model is given by the so-called Ginzburg-Landau approximation. Solutions to the latter are intended to approximately represent solutions to the Ericksen-Leslie system. Indeed, we verify this presumption in two spatial dimensions. More precisely, it is shown that weak solutions of the Ginzburg-Landau approximation converge to solutions of the Ericksen-Leslie system in the energy space for all positive times of evolution. In order to do so, theory for the Euler equations invented by DiPerna and Majda on weak compactness and concentration measures is used. The second part of the work deals with a system of partial differential equations modelling magnetoviscoelastic fluids. We provide a well-posedness result in two spatial dimensions for large energies and large times. Along the verification of that conclusion, existing theory on the Ericksen-Leslie system and the harmonic map flow is deployed and suitably extended. N2 - Flüssigkristalle und polymere Flüssigkeiten finden sich in vielen technischen Anwendungen, wobei die Liquid Crystal Displays (kurz LCDs) wahrscheinlich die bekanntesten sind. Ebenso haben viele ferromagnetische Materialien Gebrauch in der Technologie gefunden, zum Beispiel als Generatoren, Transformatoren und Hard Drive Disks. Bei einigen ferromagnetischen Materialien führt die äußere Anwendung eines Magnetfeldes zu Verformungen. Dieser Effekt wird z. B. in Aktoren ausgenutzt und es wurden neue Flüssigkeiten gefunden, welche ihre eingangs induzierte Magnetisierung beibehalten. Bis heute besteht ein Problem darin, derartige Materialien korrekt zu modellieren. Für Flüssigkristalle und Flüssigkristallströmungen existieren mehrere Modelle, aber bisher hat keines von ihnen einen vollständigen Einblick in alle beobachteten Effekte liefern können. Zu Materialien, welche magnetischen, elastischen und vielleicht sogar fluiddynamischen Effekten unterliegen, ist die Literatur bezüglich der Modellierung auf mathematischer Seite eher spärlich. Bis zu einem gewissen Grad kann man die Modellierung von Flüssigkristallen und magnetoviskoelastischen Materialien durch einen Variationsansatz für das Wirkungsfunktional vereinheitlichen. Verwendet man das Prinzip der kleinsten Wirkung aus der theoretischen Physik, reduziert sich die eigentliche Aufgabe darauf, geeignete Energien zu finden, um das beobachtete Verhalten zu beschreiben. Das Verfahren führt zu Systemen zeitabhängiger partieller Differentialgleichungen, welche in dieser Arbeit betrachtet werden. Aus mathematischer Sicht bleiben grundsätzliche Fragen zu Existenz, Eindeutigkeit und Stabilität von Lösungen offen. Bezüglich des Ericksen-Leslie-Modells für nematische Flüssigkristalle ist eine Approximation dieses Modells durch die sogenannte Ginzburg-Landau-Näherung gegeben. In dieser Arbeit wird bewiesen, dass Lösungen des letzteren Modells gegen Lösungen des erstgenannten in zwei Raumdimensionen konvergieren. Präzi- se ausgedrückt wird gezeigt, dass schwache Lösungen des Ginzburg-Landau-Systems auf beliebig großen Zeitintervallen gegen Lösungen des Ericksen-Leslie-Systems konvergieren unter der Annahme, dass die Energie des physikalischen Systems beschränkt ist. Dazu wird die von DiPerna und Majda entwickelte Theorie für die Euler-Gleichungen zu Konzentrationen unter schwacher Konvergenz verwendet. Der zweite Teil der Arbeit beschäftigt sich mit einem System partieller Differentialgleichungen zur Modellierung magnetoviskoelastischer Flüssigkeiten. Wir zeigen, dass in zwei Raumdimensionen in gewissem Sinne ein wohlgestelltes Problem für beliebig große Energien und Zeiten vorliegt. Für den Beweis dieses Resultats verwenden und erweitern wir die bestehende Theorie zum Ericksen-Leslie-System und zum Wärmefluss harmonischer Abbildungen. KW - Magnetoelastizität KW - Mikromagnetismus KW - Flüssigkristall KW - Partielle Differentialgleichung KW - Schwache Kompaktheit KW - Magnetoviscoelastic Fluids KW - Nematic Liquid Crystals KW - Weak Solutions KW - Magnetoviskoelastische Flüsse KW - Nematische Flüssigkristalle KW - Schwache Lösungen Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-278271 ER - TY - JOUR A1 - Helin, Tapio A1 - Kretschmann, Remo T1 - Non-asymptotic error estimates for the Laplace approximation in Bayesian inverse problems JF - Numerische Mathematik N2 - In this paper we study properties of the Laplace approximation of the posterior distribution arising in nonlinear Bayesian inverse problems. Our work is motivated by Schillings et al. (Numer Math 145:915–971, 2020. https://doi.org/10.1007/s00211-020-01131-1), where it is shown that in such a setting the Laplace approximation error in Hellinger distance converges to zero in the order of the noise level. Here, we prove novel error estimates for a given noise level that also quantify the effect due to the nonlinearity of the forward mapping and the dimension of the problem. In particular, we are interested in settings in which a linear forward mapping is perturbed by a small nonlinear mapping. Our results indicate that in this case, the Laplace approximation error is of the size of the perturbation. The paper provides insight into Bayesian inference in nonlinear inverse problems, where linearization of the forward mapping has suitable approximation properties. KW - Bayesian inverse problems KW - Laplace approximation KW - nonlinear inverse problems Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-265399 VL - 150 IS - 2 ER - TY - RPRT A1 - Gerber, Sebastian A1 - Quarder, Jascha T1 - Erfassung von Aspekten professioneller Kompetenz zum Lehren des Simulierens und mathematischen Modellierens mit digitalen Werkzeugen. Ein Testinstrument N2 - Die Auseinandersetzung mit Simulations- und Modellierungsaufgaben, die mit digitalen Werkzeugen zu bearbeiten sind, stellt veränderte Anforderungen an Mathematiklehrkräfte in der Unterrichtsplanung und -durchführung. Werden digitale Werkzeuge sinnvoll eingesetzt, so unterstützen sie Simulations- und Modellierungsprozesse und ermöglichen realitätsnähere Sachkontexte im Mathematikunterricht. Für die empirische Untersuchung professioneller Kompetenzen zum Lehren des Simulierens und mathematischen Modellierens mit digitalen Werkzeugen ist es notwendig, Aspekte globaler Lehrkompetenzen von (angehenden) Mathematiklehrkräften bereichsspezifisch auszudeuten. Daher haben wir ein Testinstrument entwickelt, das die Überzeugungen, die Selbstwirksamkeitserwartungen und das fachdidaktische Wissen zum Lehren des Simulierens und mathematischen Modellierens mit digitalen Werkzeugen erfasst. Ergänzt wird das Testinstrument durch selbstberichtete Vorerfahrungen zum eigenen Gebrauch digitaler Werkzeuge sowie zur Verwendung digitaler Werkzeuge in Unterrichtsplanung und -durchführung. Das Testinstrument ist geeignet, um mittels Analysen von Veranstaltungsgruppen im Prä-Post-Design den Zuwachs der oben beschriebenen Kompetenz von (angehenden) Mathematiklehrkräften zu messen. Somit können in Zukunft anhand der Ergebnisse die Wirksamkeit von Lehrveranstaltungen, die diese Kompetenz fördern (sollen), untersucht und evaluiert werden. Der Beitrag gliedert sich in zwei Teile: Zunächst werden in der Testbeschreibung das zugrundeliegende Konstrukt und der Anwendungsbereich des Testinstruments sowie dessen Aufbau und Hinweise zur Durchführung beschrieben. Zudem wird die Testgüte anhand der Pilotierungsergebnisse überprüft. Im zweiten Teil befindet sich das vollständige Testinstrument. KW - GeoGebra KW - Computerunterstützter Unterricht KW - Mathematikunterricht KW - Lehrerbildung KW - Testen KW - mathematisches Modellieren KW - Simulieren KW - digitale Werkzeuge KW - Aspekte professioneller Kompetenz KW - Testinstrument Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-273597 ER - TY - THES A1 - Schmeller, Christof T1 - Uniform distribution of zero ordinates of Epstein zeta-functions T1 - Gleichverteilung von Imaginärteilen nichttrivialer Nullstellen der Epsteinschen Zetafunktion N2 - The dissertation investigates the wide class of Epstein zeta-functions in terms of uniform distribution modulo one of the ordinates of their nontrivial zeros. Main results are a proof of a Landau type theorem for all Epstein zeta-functions as well as uniform distribution modulo one for the zero ordinates of all Epstein zeta-functions asscoiated with binary quadratic forms. N2 - Die vorliegende Arbeit untersucht, bei welchen Epsteinschen Zetafunktionen die Imaginärteile der nichttrivialen Nullstellen gleichverteilt modulo eins sind. Als zentrales Ergebnis wird dies für alle Epsteinschen Zetafunktionen, die durch binäre quadratische Formen gebildet werden, bewiesen. Außerdem wird unter anderem Landau's Theorem für alle Epsteinschen Zetafunktionen gezeigt. KW - Zetafunktion KW - Epstein, Paul KW - Gleichverteilung KW - Epstein zeta-function KW - Uniform distribution modulo one KW - Landau type theorem Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-251999 ER - TY - JOUR A1 - Hellmuth, Kathrin A1 - Klingenberg, Christian T1 - Computing Black Scholes with uncertain volatility — a machine learning approach JF - Mathematics N2 - In financial mathematics, it is a typical approach to approximate financial markets operating in discrete time by continuous-time models such as the Black Scholes model. Fitting this model gives rise to difficulties due to the discrete nature of market data. We thus model the pricing process of financial derivatives by the Black Scholes equation, where the volatility is a function of a finite number of random variables. This reflects an influence of uncertain factors when determining volatility. The aim is to quantify the effect of this uncertainty when computing the price of derivatives. Our underlying method is the generalized Polynomial Chaos (gPC) method in order to numerically compute the uncertainty of the solution by the stochastic Galerkin approach and a finite difference method. We present an efficient numerical variation of this method, which is based on a machine learning technique, the so-called Bi-Fidelity approach. This is illustrated with numerical examples. KW - numerical finance KW - Black Scholes equation KW - uncertainty quantification KW - uncertain volatility KW - polynomial chaos KW - Bi-Fidelity method Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-262280 SN - 2227-7390 VL - 10 IS - 3 ER - TY - THES A1 - Mungenast, Sebastian T1 - Zur Bedeutung von Metakognition beim Umgang mit Mathematik - Dokumentation metakognitiver Aktivitäten bei Studienanfänger_innen, Entwicklung eines Kategoriensystems für Metakognition beim Umgang mit Mathematik und Erörterung von Ansatzpunkten für Metakognition in der Analysis T1 - On the significance of metacognition in the context of mathematics – Documentation of metacognitive activity in prospective students, development of a category system for metacognition in a mathematical context and discussion of Calculus-related starting points for metacognitive activity N2 - Die vorliegende Arbeit beschäftigt sich explorativ mit Metakognition beim Umgang mit Mathematik. Aufbauend auf der vorgestellten Forschungsliteratur wird der Einsatz von Metakognition im Rahmen einer qualitativen Studie bei Studienanfänger_innen aus verschiedenen Mathematik-(Lehramts-)Studiengängen dokumentiert. Unter Verwendung der Qualitativen Inhaltsanalyse nach Mayring erfolgt die Etablierung eines Kategoriensystems für den Begriff Metakognition im Hinblick auf den Einsatz in der Mathematik, das bisherige Systematisierungen erweitert. Schließlich wird der Einsatz der entsprechenden metakognitiven Aspekte am Beispiel verschiedener Begriffe und Verfahren aus dem Analysis-Unterricht exemplarisch aufgezeigt. N2 - The thesis explores metacognition in the context of mathematics. Based on the presented research literature metacognitive activity is documented as part of a qualitative study among prospective students from various mathematics programmes (including mathematics teaching). Utilising Mayring’s Qualitative Content Analysis method a category system is established, which systemises metacognition and expands upon existing categorisations. Finally, the application of its metacognitive aspects is demonstrated using the example of various concepts and methods from the German upper secondary Calculus curriculum. KW - Metakognition KW - Mathematikunterricht KW - Hochschuldidaktik KW - Mathematik KW - Mathematikdidaktik KW - Mathematiklernen Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-293114 ER - TY - THES A1 - Nedrenco, Dmitri T1 - Axiomatisieren lernen mit Papierfalten : Entwicklung, Durchführung und Auswertung eines Hochschulkurses für gymnasiale Lehramtsstudierende T1 - Learning how to axiomatise with paperfolding N2 - In dieser Arbeit wird mathematisches Papierfalten und speziell 1-fach-Origami im universitären Kontext untersucht. Die Arbeit besteht aus drei Teilen. Der erste Teil ist im Wesentlichen der Sachanalyse des 1-fach-Origami gewidmet. Im ersten Kapitel gehen wir auf die geschichtliche Einordnung des 1-fach-Origami, betrachten axiomatische Grundlagen und diskutieren, wie das Axiomatisieren von 1-fach-Origami zum Verständnis des Axiomenbegriffs beitragen könnte. Im zweiten Kapitel schildern wir das Design der zugehörigen explorativen Studie, beschreiben unsere Forschungsziele und -fragen. Im dritten Kapitel wird 1-fach-Origami mathematisiert, definiert und eingehend untersucht. Der zweite Teil beschäftigt sich mit den von uns gestalteten und durchgeführten Kursen »Axiomatisieren lernen mit Papierfalten«. Im vierten Kapitel beschreiben wir die Lehrmethodik und die Gestaltung der Kurse, das fünfte Kapitel enthält ein Exzerpt der Kurse. Im dritten Teil werden die zugehörigen Tests beschrieben. Im sechsten Kapitel erläutern wir das Design der Tests sowie die Testmethodik. Im siebten Kapitel findet die Auswertung ebendieser Tests statt. N2 - In this manuscript, mathematical paper folding and specifically 1-fold origami is studied in a university context. The thesis consists of three parts. The first part is mainly devoted to the factual analysis of 1-fold origami. In the first chapter, we elaborate on the historical development of 1-fold origami, consider axiomatic foundations, and discuss how axiomatizing 1-fold origami could contribute to the understanding of the concept of an axiom. In the second chapter, we describe the design of the related exploratory study, describe our research objectives and questions. In the third chapter, 1-fold origami is mathematized, defined, and explored in depth. The second part focuses on the courses with the title "Learning how to axiomatize through paperfolding" which we designed and conducted. In the fourth chapter we describe the teaching methodology and the design of the courses, and the fifth chapter contains an excerpt of the courses. In the third part we describe the associated tests. In the sixth chapter we explain the design of the tests as well as the testing methodology. In the seventh chapter, the evaluation of these tests is carried out. KW - Mathematikunterricht KW - Axiom KW - Falten KW - Hochschule+Lehre KW - Origami KW - Axiomatisieren KW - mathematisches Papierfalten KW - 1-fach-Origami KW - one-fold-origami KW - mathematical paperfolding Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-279383 ER - TY - JOUR A1 - Weishäupl, Sebastian T1 - The weak Gram law for Hecke \(L\)-functions JF - The Ramanujan Journal N2 - We generalize a theorem by Titchmarsh about the mean value of Hardy’s \(Z\)-function at the Gram points to the Hecke \(L\)-functions, which in turn implies the weak Gram law for them. Instead of proceeding analogously to Titchmarsh with an approximate functional equation we employ a different method using contour integration. KW - Gram’s law KW - Gram points KW - Hecke eigenforms KW - Hecke L-functions Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-324404 SN - 1382-4090 VL - 60 IS - 4 ER - TY - JOUR A1 - Lu, Lu A1 - Mönius, Katja T1 - Algebraic degree of Cayley graphs over abelian groups and dihedral groups JF - Journal of Algebraic Combinatorics N2 - For a graph \(\Gamma\) , let K be the smallest field containing all eigenvalues of the adjacency matrix of \(\Gamma\) . The algebraic degree \(\deg (\Gamma )\) is the extension degree \([K:\mathbb {Q}]\). In this paper, we completely determine the algebraic degrees of Cayley graphs over abelian groups and dihedral groups. KW - Cayley graph KW - integral graph KW - algebraic degree Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-324380 SN - 0925-9899 VL - 57 IS - 3 ER - TY - JOUR A1 - Greefrath, Gilbert A1 - Oldenburg, Reinhard A1 - Siller, Hans-Stefan A1 - Ulm, Volker A1 - Weigand, Hans-Georg T1 - Mathematics students’ characteristics of basic mental models of the derivative JF - Journal für Mathematik-Didaktik N2 - The concept of derivative is characterised with reference to four basic mental models. These are described as theoretical constructs based on theoretical considerations. The four basic mental models—local rate of change, tangent slope, local linearity and amplification factor—are not only quantified empirically but are also validated. To this end, a test instrument for measuring students’ characteristics of basic mental models is presented and analysed regarding quality criteria. Mathematics students (n = 266) were tested with this instrument. The test results show that the four basic mental models of the derivative can be reconstructed among the students with different characteristics. The tangent slope has the highest agreement values across all tasks. The agreement on explanations based on the basic mental model of rate of change is not as strongly established among students as one would expect due to framework settings in the school system by means of curricula and educational standards. The basic mental model of local linearity plays a rather subordinate role. The amplification factor achieves the lowest agreement values. In addition, cluster analysis was conducted to identify different subgroups of the student population. Moreover, the test results can be attributed to characteristics of the task types as well as to the students’ previous experiences from mathematics classes by means of qualitative interpretation. These and other results of students’ basic mental models of the derivative are presented and discussed in detail. N2 - Der Begriff der Ableitung wird anhand von vier Grundvorstellungen charakterisiert. Diese werden als theoretische Konstrukte beschrieben, die auf theoretischen Überlegungen beruhen. Die vier Grundvorstellungen – lokale Änderungsrate, Tangentensteigung, lokale Linearität und Verstärkungsfaktor – werden empirisch quantifiziert und validiert. Zu diesem Zweck wird ein Testinstrument zur Messung der Charakteristika dieser Grundvorstellungen von Lernenden erstellt, bzgl. Gütekriterien ausgewertet und an Mathematikstudierenden (n = 266) getestet. Die Ergebnisse zeigen, dass die vier Grundvorstellungen der Ableitung bei den Lernenden mit unterschiedlichen Merkmalen rekonstruiert werden können. Die Tangentensteigung weist über alle Aufgaben hinweg die höchsten Übereinstimmungswerte auf. Die Übereinstimmung bei Erklärungen, die auf der Grundvorstellung der lokalen Änderungsrate beruhen, ist bei den Studierenden nicht so stark ausgeprägt, wie man es aufgrund der Rahmenbedingungen im Schulsystem durch Lehrpläne und Bildungsstandards erwarten würde. Die Grundvorstellung der lokalen Linearität spielt eine eher untergeordnete Rolle. Der Verstärkungsfaktor erzielt die geringsten Übereinstimmungswerte. Darüber hinaus wurde eine Clusteranalyse durchgeführt, um verschiedene Untergruppen der Schülerpopulation zu identifizieren. Die Testergebnisse können mittels qualitativer Interpretation auf Merkmale der Aufgabentypen sowie auf die Vorerfahrungen der Studierenden aus dem Mathematikunterricht zurückgeführt werden. Diese und weitere Ergebnisse zu den grundlegenden mentalen Modellen der Studierenden zur Ableitung werden ausführlich dargestellt und diskutiert. KW - derivative KW - basic mental models KW - structure KW - test instrument KW - Ableitung KW - Grundvorstellung KW - Struktur KW - Testinstrument Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-324317 SN - 0173-5322 VL - 44 IS - 1 ER - TY - JOUR A1 - Siller, Hans-Stefan A1 - Elschenbroich, Hans-Jürgen A1 - Greefrath, Gilbert A1 - Vorhölter, Katrin T1 - Mathematical modelling of exponential growth as a rich learning environment for mathematics classrooms JF - ZDM Mathematics Education N2 - Mathematical concepts are regularly used in media reports concerning the Covid-19 pandemic. These include growth models, which attempt to explain or predict the effectiveness of interventions and developments, as well as the reproductive factor. Our contribution has the aim of showing that basic mental models about exponential growth are important for understanding media reports of Covid-19. Furthermore, we highlight how the coronavirus pandemic can be used as a context in mathematics classrooms to help students understand that they can and should question media reports on their own, using their mathematical knowledge. Therefore, we first present the role of mathematical modelling in achieving these goals in general. The same relevance applies to the necessary basic mental models of exponential growth. Following this description, based on three topics, namely, investigating the type of growth, questioning given course models, and determining exponential factors at different times, we show how the presented theoretical aspects manifest themselves in teaching examples when students are given the task of reflecting critically on existing media reports. Finally, the value of the three topics regarding the intended goals is discussed and conclusions concerning the possibilities and limits of their use in schools are drawn. KW - basic mental models KW - exponential growth KW - mathematics classrooms KW - mathematical modelling KW - growth models Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-324393 SN - 1863-9690 VL - 55 IS - 1 ER - TY - JOUR A1 - Steuding, Jörn A1 - Tongsomporn, Janyarak T1 - On the order of growth of Lerch zeta functions JF - Mathematics N2 - We extend Bourgain’s bound for the order of growth of the Riemann zeta function on the critical line to Lerch zeta functions. More precisely, we prove L(λ, α, 1/2 + it) ≪ t\(^{13/84+ϵ}\) as t → ∞. For both, the Riemann zeta function as well as for the more general Lerch zeta function, it is conjectured that the right-hand side can be replaced by t\(^ϵ\) (which is the so-called Lindelöf hypothesis). The growth of an analytic function is closely related to the distribution of its zeros. KW - Lerch zeta function KW - Hurwitz zeta function KW - (approximate) functional equation KW - order of growth KW - exponent pairs KW - MSC 11M35 Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-303981 SN - 2227-7390 VL - 11 IS - 3 ER -