Combinatorics '90Recent Trends and Applications, Proceedings of the Conference on Corn binatorics, Gaeta PDF
Preview Combinatorics '90Recent Trends and Applications, Proceedings of the Conference on Corn binatorics, Gaeta
COMBINATORICS '90 Recent Trends and Applications ANNALS OF DISCRETE MATHEMATICS 52 General Editor: Peter L. HAMMER Rutgers University, New Brunswick, NJ, USA Advisory Editors: C. BERGE, Universite de Paris, France R.L. GRAHAM, AT&T Bell Laboratories, NJ, USA M.A. HARRISON, University of California, Berkeley, CA, USA V. KLEE, University of Washington, Seattle, WA, USA J.H . VAN LINT California Institute of Technology, Pasadena, CA, USA G.C. ROTA, Massachusetts Institute of'Technology, Cambridge, MA, USA T: TROlTER, Arizona State University, Tempe, AZ, USA CO MB I N A TORICS '90 Recent Trends and Applications Proceedings of the Conference on Corn binatorics, Gaeta, Italy, 20-27 May, I990 Edited by A. BARLOlTI Universita di Firenze Firenze, Italy A. BICHARA Universith de L'Aquila L'Aquila, Italy PV. CECCHERlNl and G. TALLlNl UniversitS di Roma ' l a Sapienza' Roma, Italy 1992 NORTH-HOLLAND -AMSTERDAM LONDON NEW YORK TOKYO ELSEVIER SCIENCE PUBLISHERS B.V. Sara Burgerhartstraat 25 P.O. Box 21 1, 1000 AE Amsterdam, The Netherlands ISBN: 0 444 89452 7 Q 1992 Elsevier Science Publishers B.V. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior written permission of the publisher, Elsevier Science Publishers 6.V ., Copyright & Permissions Department, RO. Box 521, 1000 AM Amsterdam, The Netherlands. Special regulations for readers in the U.S.A. - This publication has been registered with the Copyright Clearance Center lnc. fCCC), Salem, Massachusetts. Information can be obtained from the CCC about conditions under which photocopies of parts of this publication may be made in the U.S.A. All other copyright questions, including photocopying outside of the U.S.A, should be referred to the copyright owner, Elsevier Science Publishers 8.K unless otherwise specified. No responsibility is assumed by the publisher for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions or ideas contained ir: the material herein. pp. 519-528: Copyright not transferred This book is printed on acid-free paper. Printed in The Netherlands V Foreword Combinatorial methods have been used with great advantage in several diverse branches of pure and applied mathematics. This is not the place to analyze the many factors which have contributed to the increasing pace of developement of Combinatorics in the last few decades. Clear signs of the great interest for the progress in this wide area of Mathematics are the increming number of Journals and Conferences devoted to different aspects of combinatorial theories. The present. volume contains the proceedings of the intermtional Conference “Coin- binatorics ’90” held i n Gaeta (the ancient Caieta, a nice small town northwest of Naples) from May 20th to 2.ith 1990. The meeting was a “State of the Art” conference and the papers read were both of survey and research tfypes. The topics considrred concern latest developments in combinatorial geometries, their links with foundations of geometry and algebra, graph theory and various applications. We are indebted to the following institutions and sponsors for financial support: Uni- versity of Rome “La Sapienza”, “Presidenza della Facolt& di Scienze” of the University “La Sapienza” , “Consiglio Nazionale delle Ricerche” , “Gruppo Nazionale per le Strut- ture Algehriche e Geometriche e loro Applicazioni” of the C.N.R., “Azienda Autonoma di Soggiorno e Turisino di Ga.eta”, “Comune di Gaeta.”, and “Ca.sa. Editrice Liguori” (Na.ples). We also wish to express our warmest thanks to the referees for their invaluable assistence. Adriano Barlotti Alessandro Bichara Pier Vittorio Ceccherini Giuseppe Talliiii This Page Intentionally Left Blank vii Contents FOREWORD V M. AIGNER, E. TRIESCH and Z. TUZA Irregular assignments and vertex-distinguishing edge-colorings of graphs 1 A. ASTIE’-VIDAL, V. DUGAT and Z. TUZA Construction of non-isomorphic regular tournaments 11 W. BENZ On structures T( t ,q , r , n) 25 D. BETTEN and M. BR.AUN A tactical decomposition for incidence structures 37 A. BICHARA and S. INNAMORATI Note on a. chamcterimtion of Segre variety in PG(r,q ) 45 A. BONISOLI and G. KORCHMAROS A property of sharply 3-transitive finite permutation sets 49 A. BOWLER. Faithful orbits in symmetric designs 61 F. BUEKENHOUT Minimal flagtransitive geometries 69 V. CAVACCINI and A. LETTIERI Some results on hyperarchimedean MV-algebras 71 W. CHU Three combinatorial sequences derivable from the lattice path counting 81 J.R. CLAY Compound closed cha.ins in circular planar nearrings 93 M. CORDER0 p-primitive semifield planes 107 M.J. DE RESMINI The fractal-like Steiner triple system 119 ... V l l l Contents A. DEL FRA, D. GHINELLI and A. PASINI Locally partial geometries with different types of residues 127 A. DEL FRA, D. GHINELLI and S.E. PAYNE (0, n)-sets in a generalized quadrangle 130 F. EUGENI Combinatorics and cryptography 159 G. FAINA Recent intrinsic characterizations of ovoids and elliptic quadrics in PG(3, I<) 175 F. GAETA A natural association of PGL(V)-orbits in the Segre variety (P(V))’” with flags and Young tableaux 191 T.S. GRIGGS, M.J. DE RESMINI and A. ROSA Decomposing Steiner triple systems into four-line configurations 215 H. GROPP Non-symmetric configurations with deficiencies 1 and 2 227 E. HAHN Chamcterizing 1inea.r spaces by blocking sets 24 1 D.R. HUGHES Partial geometries of rank n 249 A.A. IVANOV The minimal paxabolic geometry of the Conway group Col is simply connected 259 2. JANKO Coset enumeration in groups and constructions of symmetric designs 275 V. JHA and N.L. JOHNSON On the ubiquity of Denniston-type translation ovals in generalized Andld planes 279 N.L. JOHNSON Transla tion planes and related com binatorid structures 297 H. KARZEL Finite reff exion groups and their corresponding structures 317 W.-F. KE On nonisomorphic BIBD with identical para.meters 337 Contents ix M. MARCH1 Incidence loops and their geometry 347 D.B. MEISNER Families of Menon difference sets 365 N. MELONE On the characterization problem for finite linear spaces 381 K. METSCH Linear spaces in which every line of maximal degree meets only few lines 39 1 A. PASINI and S. YOSHIARA Flag-transitive Buekenhou t geometries 403 S.E. PAYNE Collineations of the generalized quadrangles associated with q-clans 449 S. PIANTA Projective embedding of fibered groups and the Suzuki groups 463 G.F. PILZ Codes, block designs, fiobenius groups and new-rings 471 A.R. PRINCE The flag-transitive f i n e p lanes of order 27 477 D. SENATO and A. VENEZIA Symmetric functions and bijective identities 501 H. SHEN On the existence of newly Kirkman systems 511 J. SIMONIS Codes and semilinear spaces 519 J.A. THAS Old and new results on spreads and ovoids of finite classical polar spaces 529 Z. TUZA Large partial parallel classes in Steiner systems 545 B.J. WILSON Minimal line distinguishing colourings in graphs 549 Q. XIANG Some results on -1 multiplier of difference lists 559
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