Contemporary Problems In Mathematical Physics: Proceedings Of The Fourth International Workshop, Cotonou, Republic Of Benin 5 - 11 November 2005

Contemporary Problems in Mathematical Physics editors Jan Govaerts ML Korbert Hounkonnou Alfred Z. Msezane World Scientific Contemporary Problems in Mathematical Physics Proceedings of the Fourth International Workshop on Contemporary Problems in Mathematical Physics Cotonou, Republic of Benin 5-11 November 2005 editors JanGovaerts Catholic University of Louvain, Belgium M.NorbertHounkonnou University of Abomey-Calavi, Republic of Benin Alfred Z.Msezane Clark Atlanta University, USA YJ? World Scientific NEW JERSEY • LONDON • SINGAPORE • BEIJING • SHANGHAI • HONG KONG • TAIPEI • CHENNAI Published by World Scientific Publishing Co. Pte. Ltd. 5 Toh Tuck Link, Singapore 596224 USA office: 27 Warren Street, Suite 401-402, Hackensack, NJ 07601 UK office: 57 Shelton Street, Covent Garden, London WC2H 9HE British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library. CONTEMPORARY PROBLEMS IN MATHEMATICAL PHYSICS Proceedings of the Fourth International Workshop Copyright © 2006 by World Scientific Publishing Co. Pte. Ltd. All rights reserved. This book, or parts thereof, may not be reproduced in any form or by any means, electronic or mechanical, including photocopying, recording or any information storage and retrieval system now known or to be invented, without written permission from the Publisher. For photocopying of material in this volume, please pay a copying fee through the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, USA. In this case permission to photocopy is not required from the publisher. ISBN 981-256-853-0 Printed in Singapore by Mainland Press V Foreword This volume is the Proceedings of the Fourth International Workshop on Contemporary Problems in Mathematical Physics, which was held in Cotonou (Republic of Benin) from November 5 t h to 1 1 t h , 2005. Being the fourth such scientific gathering, following the First, Second and Third Workshops on Contemporary Problems in Mathematical Physics also organised in Cotonou from October 31 s t to November 5 t h , 1999, October 28 t h to November 2 n d , 2001, and November 1 s t to 7 t h , 2003, respectively, these scientific events have now become a scientific tradition in Western Africa, called to take place on this regular basis every second year in the Republic of Benin, and which its participants are eagerly looking forward to. These COPROMAPH conferences, the acronym by which they have now become known, are organised under the auspices of the International Chair in Mathematical Physics and Applications (ICMPA) located in Cotonou, within the University of Abomey-Calavi, Republic of Benin. The Proceedings of each of the COPROMAPH editions are available as a series of volumes published by World Scientific Publishing, Singapore. Scientific meetings such as the COPROMAPH Workshops provide a unique opportunity for mathematical and theoretical physicists of the African continent to meet and initiate stimulating collaborations both within Africa as well as with scientists from other parts of the world also attending these events. In particular, it is hoped that the greatest benefits will go to the younger generations of African scientists, whose responsability it is to build the basis for a scientific and technological tra