A solution to the Pompeiu problem

Let $f \in L_{loc}^1 (\R^n)\cap \mathcal{S}$, where $\mathcal{S}$ is the Schwartz class of distributions, and $$\int_{\sigma (D)} f(x) dx = 0 \quad \forall \sigma \in G, \qquad (*)$$ where $D\subset \R^n$ is a bounded domain, the closure $\bar{D}$ of which is diffeomorphic to a closed ball, and $S$ is its boundary. Then the comp$is connected and path connected. By$G$the group of all rigid motions of$\R^n is denoted. This group consists of all translations and rotations. A proof of the following theorem is given. Theorem 1. {\it Assume that n=2$,$f\not\equiv 0$, and (*) holds. Then$D is a ball.} Corollary. {\it If the problem (\nabla^2+k^2)u=0$in$D$,$u_N|_S=0$,$u|_S=const\neq 0$has a solution, then$D is a ball.} Here N$is the outer unit normal to$S$

Spherical Spectral Synthesis and Two-Radius Theorems on Damek-Ricci Spaces

We prove that spherical spectral analysis and synthesis hold in Damek-Ricci spaces and derive two-radius theorems

Complex-Distance Potential Theory and Hyperbolic Equations

An extension of potential theory in R^n is obtained by continuing the Euclidean distance function holomorphically to C^n. The resulting Newtonian potential is generated by an extended source distribution D(z) in C^n whose restriction to R^n is the delta function. This provides a natural model for extended particles in physics. In C^n, interpreted as complex spacetime, D(z) acts as a propagator generating solutions of the wave equation from their initial values. This gives a new connection between elliptic and hyperbolic equations that does not assume analyticity of the Cauchy data. Generalized to Clifford analysis, it induces a similar connection between solutions of elliptic and hyperbolic Dirac equations. There is a natural application to the time-dependent, inhomogeneous Dirac and Maxwell equations, and the `electromagnetic wavelets' introduced previously are an example.Comment: 25 pages, submited to Proceedings of 5th Intern. Conf. on Clifford Algebras, Ixtapa, June 24 - July 4, 199

Distributions and Integration in superspace

Distributions in superspace constitute a very useful tool for establishing an integration theory. In particular, distributions have been used to obtain a suitable extension of the Cauchy formula to superspace and to define integration over the superball and the supersphere through the Heaviside and Dirac distributions, respectively. In this paper, we extend the distributional approach to integration over more general domains and surfaces in superspace. The notions of domain and surface in superspace are defined by smooth bosonic phase functions $g$. This allows to define domain integrals and oriented (as well as non-oriented) surface integrals in terms of the Heaviside and Dirac distributions of the superfunction $g$. It will be shown that the presented definition for the integrals does not depend on the choice of the phase function $g$ defining the corresponding domain or surface. In addition, some examples of integration over a super-paraboloid and a super-hyperboloid will be presented. Finally, a new distributional Cauchy-Pompeiu formula will be obtained, which generalizes and unifies the previously known approaches.Comment: 25 page

Cauchy-Pompeiu type formulas for d-bar on affine algebraic Riemann surfaces and some applications

We have obtained the explicit versions and precisions for the Hodge-Riemann decomposition of formes on affine algebraic curve V. The main application consists in the construction of Faddeev-Green function for Laplacian on V. Basing on this [HM](arXiv:0804.3951 and J.Geom.Anal., 2008,18), we extended from the case X in C to the case of bordered Riemann surface X in V the R.Novikov (1988) scheme for the effective reconstruction of conductivity function sigma on X through Dirichlet-to-Neumann mapping on bX for solutions of d(sigma d^cU)=0. In Sec.4 we give a correction of the paper [HM]

Function Theoretic Methods for the Analytical and Numerical Solution of Some Non-linear Boundary Value Problems with Singularities

The p-Laplace equation is a nonlinear generalization of the well-known Laplace equation. It is often used as a model problem for special types of nonlinearities, and therefore it can be seen as a bridge between very general nonlinear equations and the linear Laplace equation, too. It appears in many problems for instance in the theory of non-Newtonian fluids and fluid dynamics or in rockfill dam problems, as well as in special problems of image restoration and image processing. The aim of this thesis is to solve the p-Laplace equation for 1 < p < 2, as well as for 2 < p < 3 and to find strong solutions in the framework of Clifford analysis. The idea is to apply a hypercomplex integral operator and special function theoretic methods to transform the p-Laplace equation into a p-Dirac equation. We consider boundary value problems for the p-Laplace equation and transfer them to boundary value problems for a p-Dirac equation. These equations will be solved iteratively by applying Banach’s fixed-point principle. Applying operator-theoretical methods for the p-Dirac equation, the existence and uniqueness of solutions in certain Sobolev spaces will be proved. In addition, using a finite difference approach on a uniform lattice in the plane, the fundamental solution of the Cauchy-Riemann operator and its adjoint based on the fundamental solution of the Laplacian will be calculated. Besides, we define gener- alized discrete Teodorescu transform operators, which are right-inverse to the discrete Cauchy-Riemann operator and its adjoint in the plane. Furthermore, a new formula for generalized discrete boundary operators (analogues of the Cauchy integral operator) will be considered. Based on these operators a new version of discrete Borel-Pompeiu formula is formulated and proved. This is the basis for an operator calculus that will be applied to the numerical solution of the p-Dirac equation. Finally, numerical results will be presented showing advantages and problems of this approach.Die p-Laplace-Gleichung ist eine nichtlineare Verallgemeinerung der wohlbekannten Laplace-Gleichung Die p-Laplace-Gleichung wird häufig als Referenzbeispiel für spezielle Typen von Nichtlinearitäten benutzt und kann daher auch als Brücke zwischen sehr allgemeinen nichtlinearen partiellen Differentialgleichungen und der linearen Laplace-Gleichung gesehen werden. Sie ist darüber hinaus auch das mathematische Modell für eine Reihe praxisrelevanter Probleme, wie z.B. in der Theorie nicht-newtonscher Flüssigkeiten, der Strömungsmechanik, der Durchfeuchtung von Schütt- dämmen und auch ein wichtiges Werkzeug zur Behandlung spezieller Probleme der Bildrekonstruktion und Bildverarbeitung. Das Ziel dieser Arbeit ist es, die p-Laplace-Gleichung sowohl für 1 < p < 2 als auch ür 2 < p < 3 zu lösen. Strenge Lösungen werden unter Benutzung der Clifford- Analysis konstruiert. Die Idee ist dabei, einen hyperkomplexen Integraloperator und funktionentheoretische Methoden auf die p-Laplace-Gleichung anzuwenden und diese Gleichung dadurch in eine p-Dirac-Gleichung zu transformieren, die dann besser gelöst werden kann. Es werden spezielle Randwertprobleme für die p-Laplace-Gleichung in Dirichlet-Probleme für die p-Dirac-Gleichung transformiert und dabei die Ordnung der Differentialgleichung reduziert. Die Randwertprobleme für die p-Dirac-Gleichung werden mit Hilfe des Banachschen Fixpunktprinzips iterativ analytisch gelöst. Durch Anwendung operator-theoretischer Methoden kann die Existenz und Eindeutigkeit der Lösung in bestimmten Sobolev-Räumen nachgewiesen werden. Darüber hinaus wird eine Finite Differenzenmethode auf einem gleichmäßigen Gitter in der Ebene angewandt, um die Fundamentallösung des diskreten Laplace- Operators numerisch zu berechnen. In der Folge werden daraus Fundamentallösungen des diskreten Cauchy-Riemann-Operators und seines adjungierten Operators erzeugt. Auf dieser Grundlage werden über Faltungen mit den Fundamentallösungen diskrete Teodorescu-Operatoren definiert, die rechtsinvers zum diskreten Cauchy-Riemann- Operator bzw. zum adjungierten diskreten Cauchy-Riemann-Operator sind. Weiterhin werden diskrete Randoperatoren, die analog zum Cauchyschen Integraloperator sind, eingeführt. Alle vorgenannten Operatoren werden in einer neuen Version einer diskreten Borel-Pompeiu-Formel zusammengeführt und bilden die Grundlage für eine diskrete Operatorenrechnung. Diese Untersuchungen erweitern bekannte Resultate auf wesentlich größere Funktionenklassen als bisher möglich waren. Die diskrete Opera- torenrechnung wird benutzt, um die diskretisierten Randwertprobleme für die p-Dirac- Gleichung numerisch zu lösen. Numerische Resultate werden vorgestellt und diskutiert. Dabei wird auf Vor- und Nachteile der entwickelten Methode eingegangen

Morera Theorems for Complex Manifolds

AbstractWe prove Morera theorems for the Radon transform integrating on geodesic spheres on complex analytic manifolds of arbitrary dimension. To avoid pathologies, we assume that the radius of each sphere of integration is less than the injectivity radius at its center. The proofs of the main results are local, and they involve the microlocal properties of associated Radon transforms and a theorem of Hörmander, Kawai, and Kashiwara on microlocal singularities. We consider Morera theorems for spheres of fixed radius and spheres of arbitrary radius

Generalizing evolution equations in ostensible metric spaces: Timed right-hand sleek solutions provide uniqueness of first-order geometric examples.

The mutational equations of Aubin extend ordinary differential equations to metric spaces (with compact balls). In first-order geometric evolutions, however, the topological boundary need not be continuous in the sense of Painleve–Kuratowski. So this paper suggests a generalization of Aubin’s mutational equations that extends classical notions of dynamical systems and functional analysis beyond the traditional border of vector spaces: Distribution– like solutions are introduced in a set just supplied with a countable family of (possibly non-symmetric) distance functions. Moreover their existence is proved by means of Euler approximations and a form of “weak” sequential compactness (although no continuous linear forms are available beyond topological vector spaces). This general framework is applied to a first-order geometric example, i.e. compact subsets of the Euclidean space evolving according to the nonlocal properties of both the current set and its proximal normal cones. Here neither regularity assumptions about the boundaries nor the inclusion principle are required. In particular, we specify sufficient conditions for the uniqueness of these solutions