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This paper reports on the historical development of the Runge-Kutta methods beginning with the simple Euler method up to an embedded 13-stage method. Moreover, the design and the use of those methods under error order, stability and computation time conditions is edited for students of numerical analysis at undergraduate level. The second part presents applications in natural sciences, compares different methods and illustrates some of the difficulties of numerical solutions.
We study the minimal and maximal closed extension of a differential operator A on a manifold B with conical singularities, when A acts as an unbounded operator on weighted Lp-spaces over B,1 < p < ∞. Under suitable ellipticity assumptions we can define a family of complex powers A up(z), z ∈ C. We also obtain sufficient information on the resolvent of A to show the boundedness of the pure imaginary powers. Examples concern unique solvability and maximal regularity of the solution of the Cauchy problem u' - Δu = f, u(0) = 0, for the Laplacian on conical manifolds.
The evolution of the closed Friedmann Universe with a packet of short scalar waves is considered with the help of the Wheeler-DeWitt equation. The packet ensures conservation of homogeneity and isotropy of the metric on average. It is shown that during tunneling the amplitudes of short waves of a scalar field can increase catastrophically promptly if their influence to the metric is not taken into account. This effect is similar to the Rubakov-effect of catastrophic particle creation calculated already in 1984. In our approach to the problem it is possible to consider a self- consistent dynamics of the expansion of the Universe and amplification of short waves. It results in a decrease of the barrier and interruption of amplification of waves, and we get an exit of the wave function from the quantum to the classically available region.
This work is an introduction to anisotropic spaces, which have an ω-weight of analytic functions and are generalizations of Lipshitz classes in the polydisc. We prove that these classes form an algebra and are invariant with respect to monomial multiplication. These operators are bounded in these (Lipshitz and Djrbashian) spaces. As an application, we show a theorem about the division by good-inner functions in the mentioned classes is proved.
For several applications it is very useful to classify the linear or non-linear mappings by their summability properties. Absolutely summing operators and polynomials are prominent and classical examples of such setting. Here we are interested in the larger class of almost summing polynomials and we investigate their connections to other related notions of summability.
Adiabatic vacuum states are a well-known class of physical states for linear quantum fields n Robertson-Walker spacetimes. We extend the definition of adiabatic vacua to general spacetime manifolds by using the notion of the Sobolev wavefront set. This definition is also applicable to interacting field theories. Hadamard states form a special subclass of the adiabatic vacua. We analyze physical properties of adiabatic vacuum representations of the Klein-Gordon field on globally hyperbolic spacetme manifolds (factoriality, quasiequivalence, local definteness, Haag duality) and construct them explicitly, if the manifold has a compact Cauchy surface.
Boundary value problems for (pseudo-) differential operators on a manifold with edges can be characterised by a hierarchy of symbols. The symbol structure is responsible or ellipicity and for the nature of parametrices within an algebra of "edge-degenerate" pseudo-differential operators. The edge symbol component of that hierarchy takes values in boundary value problems on an infinite model cone, with edge variables and covariables as parameters. Edge symbols play a crucial role in this theory, in particular, the contribution with holomorphic operatot-valued Mellin symbols. We establish a calculus in s framework of "twisted homogenity" that refers to strongly continuous groups of isomorphisms on weighted cone Sobolev spaces. We then derive an equivalent representation with a particularly transparent composition behaviour.
Dieser Beitrag zum Band 17 der HISTORY OF MATHEMATICS (Prag 2001) stellt unter den Untertiteln 1. Messung und Stetigkeit 2. Axiomatische Fixierung der euklidischen Geometrie 3. Verallgemeinerung zur Riemannschen Geometrie 4. Liesche Gruppen 5. Diskontinuierliche Bewegungsgruppen 6. Verallgemeinerte diskontinuierliche Bewegungsggruppen eine erweiterte Fassung des gleichlautenden Beitrags zum Sammelband MATHEMATIK-INTERDISZIPLINÄR (Shaker Verlag, Aachen 2000) dar. Da es sich um das Manuskript eines Vortrages am 2. Mai 2001 vor Lehrerbildnern der Karlsuniversität handelt, wird hier zusätzlich die Ersetzung der Stetigkeitsaxiome durch die Axiome des Zirkels, die zur analytischen Geometrie des dreidimensionalen Raumes über einem euklidischen Zahlkörper führt, diskutiert.
Zwei Jahrtausende wurde die Mathematik in der Sprache der Geometrie formuliert; bis ins 18. Jahrhundert wurde Geometrie synonym für Mathematik gebraucht. Auch wenn die Geometrie nicht mehr diese Stellung in der Mathematik besitzt und den Charakter einer Naturwissenschaft verloren hat, so hat sie seitdem doch wesentlich die Entwicklung der Mathematik und Naturwissenschaft beeinflusst, und ihre Sprache bewährt sich auch in Disziplinen, die sich in unserem Jahrhundert herausgebildet haben. Überzeugt von einer verkürzten Wiederholung der Wissenschaftsentwicklung in der Ontogenese der Erkenntnis der Welt, wird man speziell der Elementargeometrie stets einen gebührenden Platz einräumen, wird man immer, wenn nicht gar mit Liebhabern, so doch mit Interessenten an diesem Gegenstand rechnen können, insbesondere unter den aktiven Lehrern und den Lehramtskandidaten. In erster Linie wird ihnen die Lektüre dieses Buches empfohlen. Dabei stehen Phänomene zwar am Anfang, aber es geht vordergründig um begriffliche Präzisierung und einen (evtl. noch zu erlernenden) folgerichtigen Aufbau, beides beispielhaft in bezug auf Elementarmathematik insgesamt, auch wenn die erworbenen Fähigkeiten in der Schule dann nur zum lokalen Ordnen genutzt werden. Es wird keine Perfektion im logischen Schließen vorausgesetzt und durch die zahlreichen Zeichnungen dem anschaulichen Überbrücken von Klippen sogar Vorschub geleistet, aber es werden metamathematische Betrachtungen eingestreut, und es wird über Beweis- und Konstruktionsaufgaben permanent "Selbsttätigkeit nach den zuvor ausgeführten Beispielen" angeregt und abverlangt. Dabei kann sich der Leser fortwährend und reflektierend an den Regeln des natürlichen Schließens und damit an den wichtigsten Beweisverfahren im Anhang 1.7 orientieren. Logische Strenge wird so als nicht ein für alle mal vorgegeben, sondern als erlern- und steigerbar begriffen. Das erste Kapitel hat die Euklidische Elementargeometrie zum Inhalt, schrittweise aufgebaut auf Grundbegriffen und Axiomen. Dabei steht eine fiktive Erfahrungswelt der Kinder im Hintergrund, beispielsweise bei den Bewegungen von Figuren oder den Geraden als angeordneten Punktmengen. Um die Geometrie relativ lange im Sinne von TARSKI elementar aufbauen zu können, werden z.B. Längen und Winkelgrößen als Äquivalenzklassen betrachtet, sichern zunächst Axiome des Zirkels Konstruktion mit Zeichengeräten und den Beweis von Kongruenzsätzen ab, werden auch Drehwinkel und Schubvektoren (gerichtete Abstände) als Äquivalenzklassen begriffen. Erst im Abschnitt 1.5 wird die Vervielfachung von gerichteten Strecken mit ganzen, rationalen und reellen Zahlen realisiert, wobei der letzte Schritt ein Stetigkeitsaxiom erforderte. Auf dieser nicht mehr ganz elementaren Stufe werden Ähnlichkeit, Flächen- und Rauminhalte sowie die Theorie der Konstruktionen mit Zirkel und Lineal erörtert, insbesondere die Unlösbarkeit gewisser Aufgaben. Das zweite Kapitel bezweckt mit der Darstellung nichteuklidischer Geometrien nicht nur eine Erweiterung bisher gewonnener geometrischer Kenntnisse, sondern eine wesentliche Vertiefung des Raumbegriffes, indem Aufgabenstellungen, die im ersten Kapitel formuliert wurden, unter veränderten Rahmenbedingungen auf Lösbarkeit untersucht werden. Das geschieht zunächst für die Lobacevskijsche Geometrie mit einem Ausblick auf elliptische Geometrie und dann für die Banach- Minkowskischen Geometrien, also ausschließlich für solche Theorien, die DAVID HILBERT in seinem berühmten Vortrag "Mathematische Probleme" 1900 in Paris auf dem 2. Internationalen Mathematikerkongress als "der euklidischen Geometrie nächststehend" bezeichnet hat.
Diskontinuierliche Bewegungsgruppen sind als Symmetriegruppen von gewissen Mustern intuitiv zu erfassen. Diskontinuität einer Bewegungsggruppe B wird hier mittels Punktorbits definiert. Im Rahmen der euklidischen Geometrie endlicher Dimension findet man als (untereinander äquivalente) charakterisierende Eigenschaften diskontinuierlicher Bewegungsgruppen z. B. die lokale Endlichkeit (LEO) der Orbits nach Hilbert und COHN/VOSSEN und die Isoliertheit der Punkte in Ihrem Orbit (IPO) nach L. FEJES TOTH. In früheren Arbeiten wurde von KLOTZEK gezeigt, dass durch LEO und IPO in jedem unendlich dimensionalen Hilbertraum verschiedene Klassen von Gruppen beschrieben werden, andererseits sind LEO und IPO in metrischen Räumen gleichwertig, in denen jede beschränkte Menge präkompakt ist. Die Frage ob solche Bedingungen stets äquivalent sind hat die spätere Einführung eines ganzen Systems von ähnlichen Bedingungen initiert; hinzu kam der Wunsch, über verallgemeinerte diskontinuierliche Bewegungsggruppen, die noch nicht "kontinuierlich" wirken, weitere Muster zu beschreiben (vgl. etwa GRÜNBAUM). Die schwächste der in diesem Zusammenhang diskutierten Bedingungen führt zu Gruppen, die einerseits keine im dreidimensionalen Raum dichtliegende Punktorbits erzeugen, andererseits aber in jeder Umgebung der Identität weitere nichtidentische Bewegungen enthalten. Die Bestimmung aller Raumgruppen dieses Typs ist Gegenstand der vorliegenden Arbeit. Während 194 der 230 bekannten Raumgruppen unter Wahrung von kB (kristallographischen Beschränkung) 285 derartige Verallgemeinerungen zulassen, können ohne kB sogar überabzählbar viele schwachsdikontinuierliche Gruppen beschrieben werden.
A function has vanishing mean oscillation (VMO) on R up(n) if its mean oscillation - the local average of its pointwise deviation from its mean value - both is uniformly bounded over all cubes within R up(n) and converges to zero with the volume of the cube. The more restrictive class of functions with vanishing lower oscillation (VLO) arises when the mean value is replaced by the minimum value in this definition. It is shown here that each VMO function is the difference of two functions in VLO.
We introduce the calculus of Mellin pseudodifferential operators parameters based on "twisted" operator-valued Volterra symbols as well aas the abstract Mellin calclus with holomorphic symbols. We establish the properties of the symblic and operational calculi, and we give and make use of explicit oscillatory integral formulas on the symbolic side, e. g., for the Leibniz-product, kernel cut-off, and Mellin quantization. Moreover, we introduce the notion of parabolicity for the calculi of Volterra Mellin operators, and construct Volterra parametrices for parabolic operators within the calculi.
We consider general parabolic systems of equations on the infinite time interval in case of the underlying spatial configuration is a closed manifold. The solvability of equations is studied both with respect to time and spatial variables in exponentially weighted anisotropic Sobolev spaces, and existence and maximal regularity statements for parabolic equations are proved. Moreover, we analyze the long-time behaiour of solutions in terms of complete asymptotic expansions. These results are deduced from a pseudodifferential calculus that we construct explicitly. This algebra of operators is specifically designed to contain both the classical systems of parabolic equations of general form and their inverses, parabolicity being reflected purely on symbolic level. To this end, we assign t = ∞ the meaning of an anisotropic conical point, and prove that this interprtation is consistent with the natural setting in the analysis of parabolic PDE. Hence, major parts of this work consist of the construction of an appropriate anisotropiccone calculus of so-called Volterra operators. In particular, which is the most important aspect, we obtain the complete characterization of the microlocal and the global kernel structure of the inverse of parabolicsystems in an infinite space-time cylinder. Moreover, we obtain perturbation results for parabolic equations from the investigation of the ideal structure of the calculus.
We consider general parabolic systems of equations on the infinite time interval in case of the underlying spatial configuration is a closed manifold. The solvability of equations is studied both with respect to time and spatial variables in exponentially weighted anisotropic Sobolev spaces, and existence and maximal regularity statements for parabolic equations are proved. Moreover, we analyze the long-time behaiour of solutions in terms of complete asymptotic expansions. These results are deduced from a pseudodifferential calculus that we construct explicitly. This algebra of operators is specifically designed to contain both the classical systems of parabolic equations of general form and their inverses, parabolicity being reflected purely on symbolic level. To this end, we assign t = ∞ the meaning of an anisotropic conical point, and prove that this interprtation is consistent with the natural setting in the analysis of parabolic PDE. Hence, major parts of this work consist of the construction of an appropriate anisotropiccone calculus of so-called Volterra operators. In particular, which is the most important aspect, we obtain the complete characterization of the microlocal and the global kernel structure of the inverse of parabolicsystems in an infinite space-time cylinder. Moreover, we obtain perturbation results for parabolic equations from the investigation of the ideal structure of the calculus.
We consider general parabolic systems of equations on the infinite time interval in case of the underlying spatial configuration is a closed manifold. The solvability of equations is studied both with respect to time and spatial variables in exponentially weighted anisotropic Sobolev spaces, and existence and maximal regularity statements for parabolic equations are proved. Moreover, we analyze the long-time behaiour of solutions in terms of complete asymptotic expansions. These results are deduced from a pseudodifferential calculus that we construct explicitly. This algebra of operators is specifically designed to contain both the classical systems of parabolic equations of general form and their inverses, parabolicity being reflected purely on symbolic level. To this end, we assign t = ∞ the meaning of an anisotropic conical point, and prove that this interprtation is consistent with the natural setting in the analysis of parabolic PDE. Hence, major parts of this work consist of the construction of an appropriate anisotropiccone calculus of so-called Volterra operators. In particular, which is the most important aspect, we obtain the complete characterization of the microlocal and the global kernel structure of the inverse of parabolicsystems in an infinite space-time cylinder. Moreover, we obtain perturbation results for parabolic equations from the investigation of the ideal structure of the calculus.
The inhomogeneous ∂-equations is an inexhaustible source of locally unsolvable equations, subelliptic estimates and other phenomena in partial differential equations. Loosely speaking, for the anaysis on complex manifolds with boundary nonelliptic problems are typical rather than elliptic ones. Using explicit integral representations we assign a Fredholm complex to the Dolbeault complex over an arbitrary bounded domain in C up(n).
In this paper, we study the existence of positive solutions of a one-parameter family of logistic equations on R+ or on R. These equations are stationary versions of the Fisher equations and the KPP equations. We also study the blow up region of a sequence of the solutions when the parameter approachs a critical value and the nonexistence of positive solutions beyond the critical value. We use the direct method and the sub and super solution method.
We consider the norm closure A of the algebra of all operators of order and class zero in Boutet de Monvel's calculus on a manifold X with boundary ∂X. We first describe the image and the kernel of the continuous extension of the boundary principal symbol homomorphism to A. If X is connected and ∂X is not empty, we then show that the K-groups of A are topologically determined. In case the manifold, its boundary, and the cotangent space of its interior have torsion free K-theory, we get Ki(A,k) congruent Ki(C(X))⊕Ksub(1-i)(Csub(0)(T*X)),i = 0,1, with k denoting the compact ideal, and T*X denoting the cotangent bundle of the interior. Using Boutet de Monvel's index theorem, we also prove that the above formula holds for i = 1 even without this torsion-free hypothesis. For the case of orientable, two-dimensional X, Ksub(0)(A) congruent Z up(2g+m) and Ksub(1)(A) congruent Z up(2g+m-1), where g is the genus of X and m is the number of connected components of ∂X. We also obtain a composition sequence 0 ⊂ k ⊂ G ⊂ A, with A/G commutative and G/k isomorphic to the algebra of all continuous functions on the cosphere bundle of ∂X with values in compact operators on L²(R+).
Was misst TIMSS?
(2001)
Bei der Erstellung und Interpretation mathematischer Leistungstests steht die Frage, was eine Aufgabe mißt. Der Artikel stellt mit der strukturalen oder objektiven Hermeneutik eine Methode vor, mit der die verschiedenen Dimensionen der von einer Aufgabe erfassten Fähigkeiten herausgearbeitet werden können. Dabei werden fachliche Anforderungen, Irritationsmomente und das durch die Aufgabe transportierte Bild vom jeweiligen Fach ebenso erfasst wie Momente, die man eher als Testfähigkeit bezeichnen würde.Am Beispiel einer TIMSS-Aufgabe wird diskutiert, dass das von den Testerstellern benutzte theoretische Konstrukt kaum geeignet ist, nachhaltig zu beschreiben, was eine Aufgabe misst.
This is a survey of recent results concerning the general index locality principle, associated surgery, and their applications to elliptic operators on smooth manifolds and manifolds with singularities as well as boundary value problems. The full version of the paper is submitted for publication in Russian Mathematical Surveys.
Contents: 1 Introduction 2 Statement of the problem and definitions 3 The main results 4 Proof of theorem 2 4.1 Reduction of problem (2) to functional - integral equations 4.2 The uniqueness of a solution of equation (2) 4.3 The existence of a solution of equation (2) 5 Proof of theorem 1 6 Proof of theorem 3 7 First boundary problem for hyperbolic differential equations 7.1 Statement of the problem 7.2 The formulation of the result and a sketch of the proof
Function spaces with asymptotics is a usual tool in the analysis on manifolds with singularities. The asymptotics are singular ingredients of the kernels of pseudodifferential operators in the calculus. They correspond to potentials supported by the singularities of the manifold, and in this form asymptotics can be treated already on smooth configurations. This paper is aimed at describing refined asymptotics in the Dirichlet problem in a ball. The beauty of explicit formulas highlights the structure of asymptotic expansions in the calculi on singular varieties.
The paper deals with elliptic theory on manifolds with boundary represented as a covering space. We compute the index for a class of nonlocal boundary value problems. For a nontrivial covering, the index defect of the Atiyah-Patodi-Singer boundary value problem is computed. We obtain the Poincaré duality in the K-theory of the corresponding manifolds with singularities.
Contents: Introduction 1 Edge calculus with parameters 1.1 Cone asymptotics and Green symbols 1.2 Mellin edge symbols 1.3 The edge symbol algebra 1.4 Operators on a manifold with edges 2 Corner symbols and iterated asymptotics 2.1 Holomorphic corner symbols 2.2 Meromorphic corner symbols and ellipicity 2.3 Weighted corner Sobolev spaces 2.4 Iterated asymptotics 3 The edge corner algebra with trace and potential conditions 3.1 Green corner operators 3.2 Smoothing Mellin corner operators 3.3 The edge corner algebra 3.4 Ellipicity and regularity with asymptotics 3.5 Examples and remarks
Boundary value problems for pseudodifferential operators (with or without the transmission property) are characterised as a substructure of the edge pseudodifferential calculus with constant discrete asymptotics. The boundary in this case is the edge and the inner normal the model cone of local wedges. Elliptic boundary value problems for non-integer powers of the Laplace symbol belong to the examples as well as problems for the identity in the interior with a prescribed number of trace and potential conditions. Transmission operators are characterised as smoothing Mellin and Green operators with meromorphic symbols.
Let A be a determined or overdetermined elliptic differential operator on a smooth compact manifold X. Write Ssub(A)(D) for the space of solutions to thesystem Au = 0 in a domain D ⊂ X. Using reproducing kernels related to various Hilbert structures on subspaces of Ssub(A)(D) we show explicit identifications of the dual spaces. To prove the "regularity" of reproducing kernels up to the boundary of D we specify them as resolution operators of abstract Neumann problems. The matter thus reduces to a regularity theorem for the Neumann problem, a well-known example being the ∂-Neumann problem. The duality itself takes place only for those domains D which possess certain convexity properties with respect to A.
Asymptotic algebras
(2001)
Asymptotic algebras
(2001)
It is shown that bounded solutions to semilinear elliptic Fuchsian equations obey complete asymptoic expansions in terms of powers and logarithms in the distance to the boundary. For that purpose, Schuze's notion of asymptotic type for conormal asymptotics close to a conical point is refined. This in turn allows to perform explicit calculations on asymptotic types - modulo the resolution of the spectral problem for determining the singular exponents in the asmptotic expansions.
Contents: 1 Introduction 2 Main result 3 Construction of the asymptotic solutions 3.1 Derivation of the equations for the profiles 3.2 Exsistence of the principal profile 3.3 Determination of Usub(2) and the remaining profiles 4 Stability of the samll global solutions. Justification of One Phase Nonlinear Geometric Optics for the Kirchhoff-type equations 4.1 Stability of the global solutions to the Kirchhoff-type symmetric hyperbolic systems 4.2 The nonlinear system of ordinary differential equations with the parameter 4.3 Some energies estimates 4.4 The dependence of the solution W(t, ξ) on the function s(t) 4.5 The oscillatory integrals of the bilinear forms of the solutions 4.6 Estimates for the basic bilinear form Γsub(s)(t) 4.7 Contraction mapping 4.8 Stability of the global solution 4.9 Justification of One Phase Nonlinear Geometric Optics for the Kirchhoff-type equations