Fischer decomposition by inframonogenic functions

Let D denote the Dirac operator in the Euclidean space R^m. In this paper, we present a refinement of the biharmonic functions and at the same time an extension of the monogenic functions by considering the equation DfD=0. The solutions of this "sandwich" equation, which we call inframonogenic functions, are used to obtain a new Fischer decomposition for homogeneous polynomials in R^m.Comment: 10 pages, accepted for publication in CUBO, A Mathematical Journa

Quaternions in Applied Sciences

After more than hundred years of arguments in favour and against quaternions, of exciting odysseys with new insights as well as disillusions about their usefulness the mathematical world saw in the last 40 years a burst in the application of quaternions and its generalizations in almost all disciplines that are dealing with problems in more than two dimensions. Our aim is to sketch some ideas - necessarily in a very concise and far from being exhaustive manner - which contributed to the picture of the recent development. With the help of some historical reminiscences we firstly try to draw attention to quaternions as a special case of Clifford Algebras which play the role of a unifying language in the Babylon of several different mathematical languages. Secondly, we refer to the use of quaternions as a tool for modelling problems and at the same time for simplifying the algebraic calculus in almost all applied sciences. Finally, we intend to show that quaternions in combination with classical and modern analytic methods are a powerful tool for solving concrete problems thereby giving origin to the development of Quaternionic Analysis and, more general, of Clifford Analysis

A CAUCHY-KOWALEVSKI THEOREM FOR INFRAMONOGENIC FUNCTIONS

In this paper we prove a Cauchy-Kowalevski theorem for the functions satisfying the system ∂xf∂x = 0 (called inframonogenic functions)

Anomalous frequency and intensity scaling of collective and local modes in a coupled spin tetrahedron system

We report on the magnetic excitation spectrum of the coupled spin tetrahedral system Cu$_{2}$Te$_{2}$O$_{5}$Cl$_{2}$ using Raman scattering on single crystals. The transition to an ordered state at T$_{N}^{Cl}$=18.2 K evidenced from thermodynamic data leads to the evolution of distinct low-energy magnetic excitations superimposed by a broad maximum. These modes are ascribed to magnons with different degree of localization and a two-magnon continuum. Two of the modes develop a substantial energy shift with decreasing temperature similar to the order parameter of other Neel ordered systems. The other two modes show only a negligible temperature dependence and dissolve above the ordering temperature in a continuum of excitations at finite energies. These observations point to a delicate interplay of magnetic inter- and intra-tetrahedra degrees of freedom and an importance of singlet fluctuations in describing a spin dynamics.Comment: 7pages, 6figures, 1tabl

Matrix approach to hypercomplex Appell polynomials

Recently the authors presented a matrix representation approach to real Appell polynomials essentially determined by a nilpotent matrix with natural number entries. It allows to consider a set of real Appell polynomials as solution of a suitable first order initial value problem. The paper aims to confirm that the unifying character of this approach can also be applied to the construction of homogeneous Appell polynomials that are solutions of a generalized Cauchy–Riemann system in Euclidean spaces of arbitrary dimension. The result contributes to the development of techniques for polynomial approximation and interpolation in non-commutative Hypercomplex Function Theories with Clifford algebras

Математические журналы и их интернационализация: первый португальский журнал “Jornal de sciencias mathematicas e astronomicas”

The article describes the historical place of the first Portuguese Journal “Jornal de sciencias mathematicas e astronómicas” (Teixeira´s Journal) during the development of the European mathematical community at the end of the 19th century