Smeared and unsmeared chiral vertex operators

We prove unboundedness and boundedness of the unsmeared and smeared chiral vertex operators, respectively. We use elementary methods in bosonic Fock space, only. Possible applications to conformal two - dimensional quantum field theory, perturbation thereof, and to the perturbative construction of the sine-Gordon model by the Epstein-Glaser method are discussed. From another point of view the results of this paper can be looked at as a first step towards a Hilbert space interpretation of vertex operator algebras.Comment: 18 pages, latex, no figure

BRST-anti-BRST Antifield formalism : The Example of the Freedman-Townsend Model

The general BRST-anti-BRST construction in the framework of the antifield-antibracket formalism is illustrated in the case of the Freedmann-Townsend model.Comment: 16 pages, Latex file, Latex errors corrected, otherwise unchange

In-flight calibration of the Hot Ion Analyser on board Cluster

The Hot Ion Analyser (HIA), part of the Cluster Ion Spectrometry experiment, has the objective to measure the three-dimensional velocity distributions of ions. Due to a variety of factors (exposure to radiation, detector fatigue and aging, changes in the operating parameters, etc.), the particles' detection efficiency changes over time, prompting for continuous in-flight calibration. This is achieved by comparing the HIA data with the data provided by the WHISPER (Waves of HIgh frequency and Sounder for Probing of Electron density by Relaxation) experiment on magnetosheath intervals, for the high-sensitivity section of the instrument, or solar wind intervals, for the low-sensitivity section. The paper presents in detail the in-flight calibration methodology, reports on the work carried out for calibrating HIA and discusses plans to extend this activity in order to ensure the instrument's highest data accuracy

Causal construction of the massless vertex diagram

The massless one-loop vertex diagram is constructed by exploiting the causal structure of the diagram in configuration space, which can be translated directly into dispersive relations in momentum space.Comment: 14 pages, LATEX with style file, corresponds to published versio

Influence of Ca substitution by Mg on the Ca3Co4O9 performances

Ca3-xMgxCo4O9 polycrystalline thermoelectric ceramics with small amounts of Mg have been synthesized by the classical solid state method. Microstructural characterizations have shown that all the Mg has been incorporated into the Ca3Co4O9 structure and no Mg-based secondary phases have been identified. Apparent density measurements have shown that samples do not modify their density until 0.05 Mg content, decreasing for higher contents. Electrical resistivity decreases and Seebeck coefficient slightly raises when Mg content increases until 0.05 Mg addition. The improvement in both parameters leads to higher power factor values than the usually obtained in samples prepared by the conventional solid state routes and close to those obtained in textured materials.Se han preparado cerámicas termoeléctricas policristalinas de Ca3-xMgxCo4O9, con pequeñas cantidades de Mg, utilizando el método clásico de estado sólido. La caracterización microestructural ha mostrado que el Mg se ha incorporado en la estructura del Ca3Co4O9 y que no se han formado fases secundarias con el Mg. Las medidas de densidad aparente han mostrado que las muestras prácticamente poseen la misma densidad hasta un contenido de 0.05 Mg, disminuyendo para contenidos mayores. La resistividad eléctrica disminuye y el coeficiente Seebeck aumenta cuando el contenido de Mg se incrementa hasta valores de 0.05. La mejora de ambos parámetros conduce a valores del factor de potencia mayores que los obtenidos en muestras preparadas por la vía convencional de estado sólido, alcanzando valores próximos a los que se encuentran en materiales texturados

Dispersive calculation of the massless multi-loop sunrise diagram

The massless sunrise diagram with an arbitrary number of loops is calculated in a simple but formal manner. The result is then verified by rigorous mathematical treatment. Pitfalls in the calculation with distributions are highlighted and explained. The result displays the high energy behaviour of the massive sunrise diagrams, whose calculation is involved already for the two-loop case.Comment: 10 pages, 1 figure, LATEX, uses kluwer.cls, some references adde