Binomial Partial Steiner Triple Systems Containing Complete Graphs
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COMBINATORICS, Volume
http://dx.doi.org/10.1090/pspum/019 PROCEEDINGS OF SYMPOSIA IN PURE MATHEMATICS Volume XIX COMBINATORICS AMERICAN MATHEMATICAL SOCIETY Providence, Rhode Island 1971 Proceedings of the Symposium in Pure Mathematics of the American Mathematical Society Held at the University of California Los Angeles, California March 21-22, 1968 Prepared by the American Mathematical Society under National Science Foundation Grant GP-8436 Edited by Theodore S. Motzkin AMS 1970 Subject Classifications Primary 05Axx, 05Bxx, 05Cxx, 10-XX, 15-XX, 50-XX Secondary 04A20, 05A05, 05A17, 05A20, 05B05, 05B15, 05B20, 05B25, 05B30, 05C15, 05C99, 06A05, 10A45, 10C05, 14-XX, 20Bxx, 20Fxx, 50A20, 55C05, 55J05, 94A20 International Standard Book Number 0-8218-1419-2 Library of Congress Catalog Number 74-153879 Copyright © 1971 by the American Mathematical Society Printed in the United States of America All rights reserved except those granted to the United States Government May not be produced in any form without permission of the publishers Leo Moser (1921-1970) was active and productive in various aspects of combin• atorics and of its applications to number theory. He was in close contact with those with whom he had common interests: we will remember his sparkling wit, the universality of his anecdotes, and his stimulating presence. This volume, much of whose content he had enjoyed and appreciated, and which contains the re• construction of a contribution by him, is dedicated to his memory. CONTENTS Preface vii Modular Forms on Noncongruence Subgroups BY A. O. L. ATKIN AND H. P. F. SWINNERTON-DYER 1 Selfconjugate Tetrahedra with Respect to the Hermitian Variety xl+xl + *l + ;cg = 0 in PG(3, 22) and a Representation of PG(3, 3) BY R. -
Second Edition Volume I
Second Edition Thomas Beth Universitat¨ Karlsruhe Dieter Jungnickel Universitat¨ Augsburg Hanfried Lenz Freie Universitat¨ Berlin Volume I PUBLISHED BY THE PRESS SYNDICATE OF THE UNIVERSITY OF CAMBRIDGE The Pitt Building, Trumpington Street, Cambridge, United Kingdom CAMBRIDGE UNIVERSITY PRESS The Edinburgh Building, Cambridge CB2 2RU, UK www.cup.cam.ac.uk 40 West 20th Street, New York, NY 10011-4211, USA www.cup.org 10 Stamford Road, Oakleigh, Melbourne 3166, Australia Ruiz de Alarc´on 13, 28014 Madrid, Spain First edition c Bibliographisches Institut, Zurich, 1985 c Cambridge University Press, 1993 Second edition c Cambridge University Press, 1999 This book is in copyright. Subject to statutory exception and to the provisions of relevant collective licensing agreements, no reproduction of any part may take place without the written permission of Cambridge University Press. First published 1999 Printed in the United Kingdom at the University Press, Cambridge Typeset in Times Roman 10/13pt. in LATEX2ε[TB] A catalogue record for this book is available from the British Library Library of Congress Cataloguing in Publication data Beth, Thomas, 1949– Design theory / Thomas Beth, Dieter Jungnickel, Hanfried Lenz. – 2nd ed. p. cm. Includes bibliographical references and index. ISBN 0 521 44432 2 (hardbound) 1. Combinatorial designs and configurations. I. Jungnickel, D. (Dieter), 1952– . II. Lenz, Hanfried. III. Title. QA166.25.B47 1999 5110.6 – dc21 98-29508 CIP ISBN 0 521 44432 2 hardback Contents I. Examples and basic definitions .................... 1 §1. Incidence structures and incidence matrices ............ 1 §2. Block designs and examples from affine and projective geometry ........................6 §3. t-designs, Steiner systems and configurations ......... -
Graph Theory Graph Theory (II)
J.A. Bondy U.S.R. Murty Graph Theory (II) ABC J.A. Bondy, PhD U.S.R. Murty, PhD Universite´ Claude-Bernard Lyon 1 Mathematics Faculty Domaine de Gerland University of Waterloo 50 Avenue Tony Garnier 200 University Avenue West 69366 Lyon Cedex 07 Waterloo, Ontario, Canada France N2L 3G1 Editorial Board S. Axler K.A. Ribet Mathematics Department Mathematics Department San Francisco State University University of California, Berkeley San Francisco, CA 94132 Berkeley, CA 94720-3840 USA USA Graduate Texts in Mathematics series ISSN: 0072-5285 ISBN: 978-1-84628-969-9 e-ISBN: 978-1-84628-970-5 DOI: 10.1007/978-1-84628-970-5 Library of Congress Control Number: 2007940370 Mathematics Subject Classification (2000): 05C; 68R10 °c J.A. Bondy & U.S.R. Murty 2008 Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act 1988, this publication may only be reproduced, stored or trans- mitted, in any form or by any means, with the prior permission in writing of the publishers, or in the case of reprographic reproduction in accordance with the terms of licenses issued by the Copyright Licensing Agency. Enquiries concerning reproduction outside those terms should be sent to the publishers. The use of registered name, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant laws and regulations and therefore free for general use. The publisher makes no representation, express or implied, with regard to the accuracy of the information contained in this book and cannot accept any legal responsibility or liability for any errors or omissions that may be made. -
The Pappus Configuration and the Self-Inscribed Octagon
View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Elsevier - Publisher Connector MATHEMATICS THE PAPPUS CONFIGURATION AND THE SELF-INSCRIBED OCTAGON. I BY H. S. M. COXETER (Communic&ed at the meeting of April 24, 1976) 1. INTRODUCTION This paper deals with self-dual configurations 8s and 93 in a projective plane, that is, with sets of 8 or 9 points, and the same number of lines, so arranged that each line contains 3 of the points and each point lies on 3 of the lines. Combinatorially there is only one 83, but there are three kinds of 9s. However, we shall discuss only the kind to which the symbol (9s)i was assigned by Hilbert and Cohn-Vossen [24, pp. 91-98; 24a, pp. 103-1111. Both the unique 8s and this particular 9s occur as sub- configurations of the finite projective plane PG(2, 3), which is a 134. The 83 is derived by omitting a point 0, a non-incident line I, all the four points on E, and all the four lines through 0. Similarly, our 9s is derived from the 134 by omitting a point P, a line 1 through P, the remaining three points on I, and the remaining three lines through P. Thus the points of the 83 can be derived from the 9s by omitting any one of its points, but then the lines of the 83 are not precisely a subset of the lines of the 9s. Both configurations occur not only in PG(2, 3) but also in the complex plane, and the 93 occurs in the real plane. -
Geometric Point-Circle Pentagonal Geometries from Moore Graphs
Also available at http://amc-journal.eu ISSN 1855-3966 (printed edn.), ISSN 1855-3974 (electronic edn.) ARS MATHEMATICA CONTEMPORANEA 11 (2016) 215–229 Geometric point-circle pentagonal geometries from Moore graphs Klara Stokes ∗ School of Engineering Science, University of Skovde,¨ 54128 Skovde¨ Sweden Milagros Izquierdo Department of Mathematics, Linkoping¨ University, 58183 Linkoping¨ Sweden Received 27 December 2014, accepted 13 October 2015, published online 15 November 2015 Abstract We construct isometric point-circle configurations on surfaces from uniform maps. This gives one geometric realisation in terms of points and circles of the Desargues configura- tion in the real projective plane, and three distinct geometric realisations of the pentagonal geometry with seven points on each line and seven lines through each point on three distinct dianalytic surfaces of genus 57. We also give a geometric realisation of the latter pentago- nal geometry in terms of points and hyperspheres in 24 dimensional Euclidean space. From these, we also obtain geometric realisations in terms of points and circles (or hyperspheres) of pentagonal geometries with k circles (hyperspheres) through each point and k −1 points on each circle (hypersphere). Keywords: Uniform map, equivelar map, dessin d’enfants, configuration of points and circles Math. Subj. Class.: 05B30, 05B45, 14H57, 14N20, 30F10, 30F50, 51E26 1 Introduction A compact Klein surface S is a surface (possibly with boundary and non-orientable) en- dowed with a dianalytic structure, that is, the transition maps are holomorphic or antiholo- morphic (the conjugation z ! z is allowed). If the surface S admits analytic structure and is closed, then the surface is a Riemann surface. -
Foundations of Projective Geometry
Foundations of Projective Geometry Robin Hartshorne 1967 ii Preface These notes arose from a one-semester course in the foundations of projective geometry, given at Harvard in the fall term of 1966–1967. We have approached the subject simultaneously from two different directions. In the purely synthetic treatment, we start from axioms and build the abstract theory from there. For example, we have included the synthetic proof of the fundamental theorem for projectivities on a line, using Pappus’ Axiom. On the other hand we have the real projective plane as a model, and use methods of Euclidean geometry or analytic geometry to see what is true in that case. These two approaches are carried along independently, until the first is specialized by the introduction of more axioms, and the second is generalized by working over an arbitrary field or division ring, to the point where they coincide in Chapter 7, with the introduction of coordinates in an abstract projective plane. Throughout the course there is special emphasis on the various groups of transformations which arise in projective geometry. Thus the reader is intro- duced to group theory in a practical context. We do not assume any previous knowledge of algebra, but do recommend a reading assignment in abstract group theory, such as [4]. There is a small list of problems at the end of the notes, which should be taken in regular doses along with the text. There is also a small bibliography, mentioning various works referred to in the preparation of these notes. However, I am most indebted to Oscar Zariski, who taught me the same course eleven years ago. -
AN INFINITE GRAPH of GIRTH 12 by ASIA Ivlfc WEISS
TRANSACTIONS of the AMERICAN MATHEMATICAL SOCIETY Volume 283. Number 2, June 1984 AN INFINITE GRAPH OF GIRTH 12 BY ASIA IVlfc WEISS Abstract. From the regular hyperbolic honeycomb {3,6,3} we derive regular honeycombs with finite numbers of toroidal cells. Joining centers of faces of these honeycombs to the midpoints of its edges we obtain trivalent symmetrical graphs. We investigate the relation between these honeycombs, their groups and the graphs embedded in them. 1. Introduction. Coxeter and Whitrow [1950, p. 429] showed that the points whose four coordinates are proportional to the integral solutions of the Diophantine equation t2 — x2 —y2 — z2 — 1 are vertices of the hyperbolic honeycomb {4,4, 3}. Coxeter suggested that it would be useful to find coordinates for all regular hyperbolic honeycombs as integral solutions of Diophantine equations since as a by-product we would obtain a simple representation for generators of the symmetry groups of these honeycombs. Garner in his Ph.D. Thesis [1964] discovered coordi- nates for two more hyperbolic honeycombs {6,3,4} and {6,3,3}. In §3 we complete these investigations by giving coordinates for all cristallographic regular hyperbolic honeycombs as well as their truncations. This is then used in §5 to find the group whose Cayley diagram is an infinite trivalent symmetrical graph of girth 12. At the Conference on Graph Theory and Combinatorial Analysis held at the University of Waterloo, R. M. Foster [1966] presented a paper which included a table of 176 trivalent symmetrical graphs. Since then there has been a search to find more. A few more of these graphs have been found by Coxeter, Frucht, Harries, and by Foster himself. -
Combinatorial Configurations, Quasiline Arrangements, And
Combinatorial configurations, quasiline arrangements, and systems of curves on surfaces J¨urgenBokowski, Jurij Koviˇc,TomaˇzPisanski, and Arjana Zitnikˇ October 7, 2014 Abstract It is well known that not every combinatorial configuration admits a geo- metric realization with points and lines. Moreover, some of them do not even admit realizations with pseudoline arrangements, i.e., they are not topologi- cal. In this paper we provide a new topological representation by using and essentially generalizing the topological representation of oriented matroids in rank 3. These representations can also be interpreted as curve arrangements on surfaces. In particular, we generalize the notion of a pseudoline arrangement to the notion of a quasiline arrangement by relaxing the condition that two pseudo- lines meet exactly once and show that every combinatorial configuration can be realized as a quasiline arrangement in the real projective plane. We also generalize well-known tools from pseudoline arrangements such as sweeps or wiring diagrams. A quasiline arrangement with selected vertices belonging to the configuration can be viewed as a map on a closed surface. Such a map can be used to distinguish between two \distinct" realizations of a combinatorial configuration as a quasiline arrangement. Keywords: pseudoline arrangement, quasiline arrangement, projective plane, in- cidence structure, combinatorial configuration, topological configuration, geometric configuration, sweep, wiring diagram, allowable sequence of permutations, maps on a surface. Math. Subj. Class. (2010): 51E20, 52C30, 05B30. arXiv:1410.2350v1 [math.CO] 9 Oct 2014 1 Introduction For a long time researchers in configurations have neglected the difference between combinatorial and geometric configurations of points and lines. In the nineteenth century it was either tacitly assumed that these concepts coincide or the emphasis was on geometric existence of configurations and the two well-known combinatorial configurations (73) and (83) were automatically excluded from consideration. -
Desargues, Doily, Dualities and Exceptional Isomorphisms
AUSTRALASIAN JOURNAL OF COMBINATORICS Volume 57 (2013), Pages 251–270 Desargues, doily, dualities and exceptional isomorphisms Bernhild Stroppel Markus Stroppel LExMath — Lehrexportzentrum Mathematik Fakult¨at f¨ur Mathematik und Physik Universit¨at Stuttgart D-70550 Stuttgart Germany [email protected] F¨ur Herrn Professor Dr. G. Pickert aus Anlass seines 95. Geburtstags. Abstract We study various graphs associated with symmetric groups. This leads to a quick understanding of automorphisms, dualities and polarities both for the Desargues configuration and the smallest generalised quadrangle. The results are used to establish the existence of outer automorphisms of the symmetric group on six symbols, and the exceptional isomorphism between the alternating group on six symbols and the little projective group of the projective line over the field with nine elements. For the latter isomorphism, we present a new proof of uniqueness for the inversive plane of order 3. 1 Introduction The Desargues configuration is an incidence structure with ten points and ten lines; it plays an important role in the foundations of geometry (see 1.3 below). It turns out that it is also of great interest of its own; this is due to its inherent symmetry. We give a sleek description of this configuration first: F F 1.1 Definition. Let be a set of 5 elements. As point set, we take the set 2 of F F all subsets of size 2 in ,theset 3 of lines consists of all subsets of size 3, and D F , F , ⊂ incidence is inclusion: := 2 3 . It seems that this labelling dates back to [12, IV, §1]. -
Thickly Resolvable Designs by Amanda Malloch B.Sc., University
Thickly Resolvable Designs by Amanda Malloch B.Sc., University of Victoria, 2007 M.Sc., University of Victoria, 2009 A Dissertation Submitted in Partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY in the Department of Mathematics and Statistics c Amanda Malloch, 2016 University of Victoria All rights reserved. This dissertation may not be reproduced in whole or in part, by photocopying or other means, without the permission of the author. ii Thickly Resolvable Designs by Amanda Malloch B.Sc., University of Victoria, 2007 M.Sc., University of Victoria, 2009 Supervisory Committee Dr. Peter Dukes, Supervisor (Department of Mathematics and Statistics) Dr. Kieka Mynhardt, Departmental Member (Department of Mathematics and Statistics) Dr. Frank Ruskey, Outside Member (Department of Computer Science) iii Supervisory Committee Dr. Peter Dukes, Supervisor (Department of Mathematics and Statistics) Dr. Kieka Mynhardt, Departmental Member (Department of Mathematics and Statistics) Dr. Frank Ruskey, Outside Member (Department of Computer Science) ABSTRACT In this dissertation, we consider a generalization of the historically significant problem posed in 1850 by Reverend Thomas Kirkman which asked whether it was possible for 15 schoolgirls to walk in lines of three to school for seven days so that no two of them appear in the same line on multiple days. This puzzle spawned the study of what we now call resolvable pairwise balanced designs, which balance pair coverage of points within blocks while also demanding that the blocks can be grouped in such a way that each group partitions the point-set. Our generalization aims to relax this condition slightly, so that each group of blocks balances point-wise coverage but each point occurs in each group σ times (instead of just once). -
DESARGUES' THEOREM Two Triangles ABC and a B C Are Said To
DESARGUES' THEOREM DONALD ROBERTSON Two triangles ABC and A0B0C0 are said to be in perspective axially when no two vertices are equal and when the three intersection points AC \A0C0, AB \A0B0 and BC\B0C0 are collinear. We say ABC and A0B0C0 are in perspective centrally when no two vertices are equal and when the intersection points A0A \ B0B, A0A \ C0C and B0B \ C0C are all equal. Girard Desargues, the father of projective geometry, proved the following theorem in the 17th century. It was first published in 1648 by Abraham Bosse. Theorem 1. Two triangles in the real projective plane are in perspective centrally if and only if they are in perspective axially. These properties of perspective only make sense when we know that any two lines intersect at exactly one point. Thus the natural setting for studying these properties is projective space, rather than the more familiar affine space. We restrict ourselves to projective planes because in higher dimensions Desargues' theorem follows from the fact that any two planes intersect in a line. 1. Affine and Projective Planes An affine plane consists of a set P of points and a set L of subsets of P satisfying the following three axioms. AP1 Any two distinct points lie on one and only one line. AP2 Given a line l and a point P not contained in l there is one and only one line which contains P and is disjoint from l. AP3 There are three points not all contained in a single line. Members of L are called lines. -
Desargues Theorem, Its Configurations, and the Solution to A
Desargues theorem, its configurations, and the solution to a long-standing enumeration problem Aiden A. Bruen ∗ 1, Trevor C. Bruen2, and James M. McQuillan3 1School of Mathematics and Statistics, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario, K1S 5B6, Canada, [email protected] 2Universit´ede Sherbrooke, Sherbrooke, Quebec, J1K 2R1, Canada, [email protected] 3School of Computer Sciences, Western Illinois University, 1 University Circle, Macomb, IL, 61455, USA, [email protected] Abstract We solve a long-standing problem by enumerating the number of non-degenerate Desargues configurations. We extend the result to the more difficult case involving Desargues blockline structures in Sec- tion 8. A transparent proof of Desargues theorem in the plane and in space is presented as a by-product of our methods. Keywords: Desargues theorem, Desargues configuration, 5-compressor, pro- jective spaces, polarity, finite field 1 Introduction, Background. arXiv:2007.09175v1 [math.CO] 17 Jul 2020 The celebrated theorems of Pappus and Desargues are the fundamental building blocks in the axiomatic development of incidence and projective geometry. Hilbert's work showed that a projective plane π over a division ring F is equivalent to one in which Desargues theorem holds, which is in ∗The first author gratefully acknowledges the financial support of the National Sciences and Engineering Research Council of Canada turn equivalent to the assumption that π is embedded in a 3-dimensional projective space. The Hessenberg theorem shows that the ancient theorem of Pappus im- plies the Desargues theorem. From this it follows that a projective plane over a commutative division ring F , i.e.