Wilfred Owen as a pacifist

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Comunicação e Expressão. Programa de Pós-Graduação em Letra

On the Rate of Quantum Ergodicity on hyperbolic Surfaces and Billiards

The rate of quantum ergodicity is studied for three strongly chaotic (Anosov) systems. The quantal eigenfunctions on a compact Riemannian surface of genus g=2 and of two triangular billiards on a surface of constant negative curvature are investigated. One of the triangular billiards belongs to the class of arithmetic systems. There are no peculiarities observed in the arithmetic system concerning the rate of quantum ergodicity. This contrasts to the peculiar behaviour with respect to the statistical properties of the quantal levels. It is demonstrated that the rate of quantum ergodicity in the three considered systems fits well with the known upper and lower bounds. Furthermore, Sarnak's conjecture about quantum unique ergodicity for hyperbolic surfaces is confirmed numerically in these three systems.Comment: 19 pages, Latex, This file contains no figures. A postscript file with all figures is available at http://www.physik.uni-ulm.de/theo/qc/ (Delay is expected to 23.7.97 since our Web master is on vacation.

Bright gap solitons of atoms with repulsive interaction

We report on the first experimental observation of bright matter-wave solitons for 87Rb atoms with repulsive atom-atom interaction. This counter intuitive situation arises inside a weak periodic potential, where anomalous dispersion can be realized at the Brillouin zone boundary. If the coherent atomic wavepacket is prepared at the corresponding band edge a bright soliton is formed inside the gap. The strength of our system is the precise control of preparation and real time manipulation, allowing the systematic investigation of gap solitons.Comment: 4 pages, 4 figure

Production of knowledge and pedagogical action

Este artigo tem por objetivo discutir critérios para que as iniciativas e os métodos de ensino que visam dinamizar o ensino escolar sejam ativos e apontar alguns indicativos da atividade do aluno na construção do conhecimento. A teoria de Piaget, como uma teoria que mostra os principais processos de construção do conhecimento, destaca sempre a ação do sujeito como fundamental neste processo. Discute-se a ação mental tomando como referência os aspectos funcionais da assimilação e da acomodação, da abstração reflexionante, do aprender fazer e o compreender, sempre estabelecendo contrapontos com as práticas escolares.This article intends to discuss the criterion for the initiatives and the teaching methods that aim to boost school teaching to be more active and show some indication of the students' activity in the construction of knowledge. Piaget's theory, as a theory that shows the main process of construction of knowledge, always points to the subject's action as the basis of this processo The functional aspects of assimilation and accommodation, of reflexive abstraction, of the know-how leaming and comprehension are taken as a reference to discuss the mental action, always establishing counterpoints with the school activities. Key-words: mental activity, knowledge construction, active methodology

Superfluid phase transition and strong-coupling effects in an ultracold Fermi gas with mass imbalance

We investigate the superfluid phase transition and effects of mass imbalance in the BCS (Bardeen-Cooper-Schrieffer)-BEC (Bose-Einstein condensation) crossover regime of an cold Fermi gas. We point out that the Gaussian fluctuation theory developed by Nozi\`eres and Schmitt-Rink and the $T$-matrix theory, that are now widely used to study strong-coupling physics of cold Fermi gases, give unphysical results in the presence of mass imbalance. To overcome this problem, we extend the $T$-matrix theory to include higher-order pairing fluctuations. Using this, we examine how the mass imbalance affects the superfluid phase transition. Since the mass imbalance is an important key in various Fermi superfluids, such as $^{40}$K-$^6$Li Fermi gas mixture, exciton condensate, and color superconductivity in a dense quark matter, our results would be useful for the study of these recently developing superfluid systems.Comment: 7 pages, 4 figures, Proceedings of QFS-201

Electronic properties of two isomeric charge transfer [2.2]paracyclophanes

The emission spectra and the zero field splitting parameters of the two diastereomeric 4,7-dicyano-12,15-dimethoxy-[2.2] paracyclophanes 3 and 4 in comparison to the corresponding monomers 1 and 2 were investigated in order to study the orientation dependence of charge transfer (CT) interactions. The general results in glasses (PMMA) are: broad structureless emission bands with large spectral overlap between fluorescence and phosphorescence; strong reduction of the zero field splitting parameters D and D* by a factor of two for the pseudo-ortho isomer 3 and by a factor of four for the pseudo-geminal isomer 4 showing the strong effect of the geometrical orientation. In single crystals of the same phanes the zero field parameters were found to be further reduced to about one fifth of the value of the monomers which indicates, in accordance with the emission spectra, an additional intermolecular interaction between adjacent phanes