On the impossibility of representing infinite utility streams

We show that, independently of the topology chosen on the set of all infinity utility streams, there is no Social Welfare Function preserving the von Weizsäcker’s overtaking criterion. With our proof we extend the impossibility result of Basu and Mitra

One dimensional description of the gravitational perturbation in a Kerr background

The perturbation equation in a Kerr background is written as a coupled system of one dimensional equations for the different modes in the time domain. Numerical simulations show that the dominant mode in the gravitational response is the one corresponding to the mode of the initial perturbation, allowing us to conjecture that the coupling among the modes has a weak influence in our system of equations. We conclude that by neglecting the coupling terms it can be obtained a one dimensional harmonic equation which indeed describes with good accuracy the gravitational response from the Kerr black hole with low spin, while only few couplings are necessary to describe a high spin one. This result may help to understand the structure of test fields in a Kerr background and even to generate accurate waveforms for various cases in an efficient manner.Comment: 14 pages, 3 figure

On the impossibility of representing infinite utility streams

We show that, independently of the topology chosen on the set of all infinity utility streams, there is no Social Welfare Function preserving the von Weizsäcker’s overtaking criterion. With our proof we extend the impossibility result of Basu and Mitra.

The Invariant Two-Parameter Function of Algebras ψ

At present, the research on invariant functions for algebras is very extended since Hrivnák and Novotný defined in 2007 the invariant functions y and j as a tool to study the Inönü–Wigner contractions (IW-contractions), previously introduced by those authors in 1953. In this paper, we introduce a new invariant two-parameter function of algebras, which we call ¯y, as a tool which makes easier the computations and allows researchers to deal with contractions of algebras. Our study of this new function is mainly focused in Malcev algebras of the type Lie, although it can also be used with any other types of algebras. The main goal of the paper is to prove, by means of this function, that the five-dimensional classical-mechanical model built upon certain types of five-dimensional Lie algebras cannot be obtained as a limit process of a quantum-mechanical model based on a fifth Heisenberg algebra. As an example of other applications of the new function obtained, its computation in the case of the Lie algebra induced by the Lorentz group SO(3, 1) is shown and some open physical problems related to contractions are also formulated.Ministerio de Ciencia e Innovación MTM2013-40455-PMinisterio de Ciencia e Innovación FQM-326 (J.N.-V.)Junta de Andalucía FQM-160 (P.P.-F.

La Sociedad Andaluza de Educación Matemática THALES, Medalla de Andalucía 2010

La Sociedad Andaluza de Educación Matemática THALES ha sido galardonada con la Medalla de Andalucía 2010, concedida por la Junta de Andalucía el 28 de febrero de 2010, Día de la Comunidad, en reconocimiento a su labor, que entre otras destaca por la innovación didáctica, la divulgación y popularización de las Matemáticas, y la organización de distintas actividades y proyectos que realiza desde su creación en 1981

Del «utile consiglio» y las «sollazzevoli cose». El Decameron en el marco de la cultura popular.

Sin resume