DOCSLIB.ORG

Lunda Geometry: Mirror Curves, Designs, Knots, Polyominoes

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Lunda Geometry: Mirror Curves, Designs, Knots, Polyominoes ISBN: 978- 1-4357-2629- 1 Copyright © 2007 by Paulus Gerdes 2 C JPYnghted matanal Paulu s Gerdes LUNDA GEOMETRY: Mirror Curves, Designs, Knots, Polyominoes, Patterns, Symmetries Universidade Pedag6gica Maputo, Mozambique 2007 3 C JPYrig eo maJ:lnal Title. LUNDA GEOMETRY: Designs, Knots Polyominoes, Patterns, Symmetrie . uthor: Paulus Gerde Research Center for Mathematics, Cultur,e and Education . P. 915 Maputo Mozambique pgerdes . irconn.com irstedition : niversidade Pedag6g.ica Maputo Mo ~ arohique 1996 ] 52 pp. (01362/FBM/96 Maputo Mozambique) Original title: Lunda Geometry: Designs, Polyominoes Patterns, Symmetries Second edition: Lulu Enterprises, MorrisviHe NC 27560 USA,2007 196 pp. Distribuition (print & download): http://stores.lulu.comlpg -rdes or search 'Paulus Gerdes ~ on the webpage: wwwJulu.cOJll opyright © 2007 by Paulus Gerdes 4 CONTENTS page Preface (First edition) 7 Preface (Second edition) 9 1 On ~' OfUl sand d.·awings, min·or curves and the 11 generation of Lunda-designs 1.1 A bout sOfia sa nd drawings 11 1.2 Towards a discovery 12 1.3 Some theorems about smooth and monolinear mirror lines 21 designs 1.4 Enumeration modulo 2 and Lunda-designs 33 2 On Lunda-designs and some ortheir symmetries 39 2.1 Mirror designs and mirror curves 39 2.2 The discovery of Lunda-designs 42 2.3 Examples 43 2.4 General symmetry properties 50 2.5 Special classes of Lunda-designs 51 2.6 Square Lunda-designs and fractals 66 2.7 Generalization of Lunda-designs 68 2.8 Hexagona l Lunda-designs 73 References 75 3 On mirror CUI"\les and Lunda-designs 77 3. 1 Mirror designs and mirror curves 77 3.2 Regular mirror curves 80 3.3 Non-regular mirror curves 82 3.4 Properties of Lunda-designs 85 3.5 Classes of Lunda-designs 86 1 6 Generalizations 89 Lunda-k-designs 90 Circular Lunda-designs 91 Polyominal Lunda-designs 92 Fractal Lunda-designs 97 References 98 5 C JPYng eo maJ:lnal 4 On Lunda-designs and Lunda-animals - Fibonacci 10 1 returns to Africa 4. 1 Introduction 101 4.2 Counting the number of possible paths of Lunda-animals 104 References 107 5 On Lunda-designs and polyominoes 109 5.1 Polyominoes in Lunda-designs 109 5.2 Types of Lunda-polyominoes 110 5.3 Approximation of the number of Lunda-n-ominoes 112 5.4 Symmetrical types 114 6 Symmetrical, closed Lunda-polyominoes 121 7 Examples of Lunda-spirals 133 8 137 8. lOne-dimensional Lunda-patterns (Lunda-strip-patterns) 137 8.2 Two-dimensional Lunda-patterns 146 Reference 160 9 On the geometry of Celtic knots and their Lunda­ 161 designs 10 Recent variations and generalizations 179 Appendix I: J89 Proofs of some theorems concerning the relations hip betvveen rectangle-filling mirror curves and Lunda- designs Books by the same author 197 6 C JPYnghted matanal PREFACE (First edition) Lunda-designs are a type of black-and-white design that I discovered while analyzing properties of a special class of sOlla sand drawings from eastern Angola and neighboring regions of Zambia and Congo / Zaire. The elements of this class are mirror-generated curves, and generate, in turn, Lunda-designs. The chapters of this book are comprised of papers on mirror curves, Lunda-designs and related concepts such as Lunda­ polyominoes and Lunda-patterns. Most chapters may be read independently of each other. Chapter I is a partial translation of Chapter 6 of the second volume of Sona Geometry, and analyses the mirror curve class of sona sand drawings and some of their basic properties. In this chapter, I also describe the discovery of Lunda-designs_ Chapters 2: and 3 present an introduction to Lunda-designs, their symmetries, and some of their generalizations such as Lunda-k-designs and hexagonal Lunda-designs, These papers were published in the international journals Visl/al Malhemalics (1999) and Compl/lers and Graphic.I' (1997) respectively_ In Chapter 4, I introduce the concepts of Lunda-polyominoes and Lunda-animals, and evaluate the number of possible paths of given lengths that may be traversed by Lunda-animals. The famous sequence of Fibonacci surprisingly appears in this context. Chapter 5 presents a first approximation for the number of Lunda-n-ominoes, In Chapters 6 and 7, I explore special classes of Lunda-polyominoes such as symmetrical closed Lunda-polyominoes and Lunda-spirals, Finally, in Chapter 8, I show that for all twenty­ four classes of one-color and two-color, one-dimensional patterns, it is possible to construct Lunda-strip-patterns, which belong to them_ Furthermore, I present examples of one-color and two-color, two­ dimensional Lunda-patterns. 7 c Appendix I presents the proof of the theorem that every mirror design generates a Lunda-design, and, inversely, for every (finite) Lunda-design a mirror design that generates it may be constructed. Lunda-designs present a concrete example of how ethnomathematical research can lead to both fruitful and interesting ideas of se ri ous mathematical reflection. I hope the book LUNDA Geumelly wi ll stimulate further research on these aesthetically attractive figures. Acknowledgements My thanks go to my colleagues at the Unil'ersidade Pedagogica (UP, Mozambique) for their permanent interest and encouragement of my research; to Jill Gerrish (Department of English, UP) for the linguistic revision. I am very grateful for the interest that colleagues in various parts of the world have shown in the preparation of this book. My thanks go, in particular, 10 Slavik Jablan (The Mathematical Institute, Belgrade, Serbia), Maurice Bazin (Exploratorium, San Francisco, USA), Erhard Scholz (Bergische Universitat, Wuppertal, Germany), Clifford Pickover (TB M Thomas Watson Research Center, New York, USA), and Arthur Powell (Rutgers University, Newark, USA) for their stimulating reactions on the chapters they have read. Above all, I thank my wife Marcela Libombo and my daughter Lesira for their encouragement. Maputo, June 25, [996 Paulus Gerdes , C JPYnghted matanal PREFACE (Second edition) The new edi tion of the book Lllnda Geometry contains two additional chapters. Chapter 9, entitled 011 the Geometry of Celtic knots and their Lllnda..(/esigns, was published in the British journal Mathematics in School (\999). Chapter lOis the last section of an invited paper presented al the Wenner-Gren International Symposium "Symmetry 2000" (Stockholm, September 13-16, 2000) and published in the proceedings. The new edition does not include the review of Solomon Golomb's book Po/yolllinoes, published in Archives infernariollales d 'Hisloire des Sciences (1998,48. No. 140, 174- 176). Chapter 4 of my book GeOIl/CllY from Africa: Malhclllaticaf and Educational Explorations, published by the MAA ( 1999), presents an introduction to Lunda-designs and includes a section on Lunda­ polyhedral-designs and a board game, The relationship between Lunda-designs and magic squares is explored in a paper published in 71le College Mathematics Journal (2000). The study of Lunda-designs led to the discovery of Liki-designs (2002a, 2002b) and of various types of matrices, including cycle matrices (see e.g. the papers published in the electronic journal Visual Mathematics). The book Adventures in the World a/Matrices (2007d) presents an introduction to cycle matrices. Further books on the beautiful geometry and linear algebra of Lunda-designs are forthcoming, The paper Llinda Symmetry where Geomelry meeli)' Al'l (2 005) explores some relationships between Lunda Geometry and art. Mathematician and artist John Sims of the Ringling School of Art and Design (Sarasota, Florida) organized a math-art exhibition including some of colorful Lunda-designs I had prepared. A book on Lunda­ designs and art is in preparation. Maputo, October 2007 Paulus Gerdes c Referellce .~ Gerdes. Paul us (1999), Geometry from Africa: Mathematical and Educational Explorations. The Mathemat ical Association of America. Washington DC __ (2000). On Lunda-designs and the con struction of associated magic squares of order 4p. The College Ma/hemalics Journal, Washington DC, 3 1(3). 182- 188 __ (2002a), New designs from Africa, Pills Magazine. Ox ford, March __ (2002b). Prom Liki-designs to cycle matrices: The discovery of atlractive new symmetries, ViSlial Ma/hemarics, Belgrade. 4(1 ) __ (2002c), m-Canonic mirror curves, Visual Malhematics. 4( I ) __ (2002d). Variazio ni sui disegni Lunda, in: Mi chele Emmer (Ed.), Malemalica e Gllllllm 2002, Springer. Milan, 135- 146 __ (2002e), tlciix matrices. Visual Marh eflla/ics, 4(2) __ (2002f), Cylinder matrices, Vimal Marlll'lIIa/ic:;, 4(2) __ (2003). forom African 'sona' drawings 10 the discovery of new symmetri es and matrices, in: Nouzha £1 Yw.:oubi e/ al. (Eds.), ProcN'diligs of rill' 13" Pall African M athemaric~' Olympiad, Min isterio da Educ a ~iio . Maputo, 5 1-64 __ (2004a), On mirror-curves, alternating kn ots. rope mats and plaited polyhedra: A Foreword, in: Ni ls Kr. Rossing & Christoph Kirfcl, Maremarisk beskrivdse av rawnarrer, NTNU. Trondheim . 9-14 __ (2005). Lunda Symmetry where Geometl)' meets Art, in : Michele Emmer (Ed.), The Visual Mind 1/, MIT Press, Boston, 335-34 8 __ (2006a), Symmetries o f alternating cycle matrices, Visual Malhemalics. 8(2) __ (2006b), On the representation and multiplication of basic altern at i ng cycle matrices. Viwal MathematiCS, 8(2) __ (2006c). Sona Geometryfrom Angola: Mathematics of an Afncall Traditioll, Polimctrica International Science Publishers, Mo nza, 232 pp. __ (2007 11), MWllni colour inversion, symmetry lind cycle matrices, Visllal MathematiCS, Belgrade, 9(3) __ (2007c). From th e African sona tradition to new types of desi gns and matrices, in: Konatc, Diall a (Ed.). Proceedings oltlle International Workshop on Mmhematical Modellillg, Siml/lmion, Visllalizmion and e­ Learning, Springer, New York (in press). __ (2007d), Advelllllres ill rlie World of Matrias, Nova Science Publishers, New York __ (2007c), The Beautifu! Geometry Wid Lineur Algebra of Lunda-Desiglls, 204 pp.
Load more

Recommended publications
  • Snakes in the Plane
    Snakes in the Plane by Paul Church A thesis presented to the University of Waterloo in fulfillment of the thesis requirement for the degree of Master of Mathematics in Computer Science Waterloo, Ontario, Canada, 2008 c 2008 Paul Church I hereby declare that I am the sole author of this thesis. This is a true copy of the thesis, including any required final revisions, as accepted by my examiners. I understand that my thesis may be made electronically available to the public. ii Abstract Recent developments in tiling theory, primarily in the study of anisohedral shapes, have been the product of exhaustive computer searches through various classes of poly- gons. I present a brief background of tiling theory and past work, with particular empha- sis on isohedral numbers, aperiodicity, Heesch numbers, criteria to characterize isohedral tilings, and various details that have arisen in past computer searches. I then develop and implement a new “boundary-based” technique, characterizing shapes as a sequence of characters representing unit length steps taken from a finite lan- guage of directions, to replace the “area-based” approaches of past work, which treated the Euclidean plane as a regular lattice of cells manipulated like a bitmap. The new technique allows me to reproduce and verify past results on polyforms (edge-to-edge as- semblies of unit squares, regular hexagons, or equilateral triangles) and then generalize to a new class of shapes dubbed polysnakes, which past approaches could not describe. My implementation enumerates polyforms using Redelmeier’s recursive generation algo- rithm, and enumerates polysnakes using a novel approach.
    [Show full text]
  • 1 2. the Lattice 2 3. the Components of Plane Symmetry Groups 3 4
    PLANE SYMMETRY GROUPS MAXWELL LEVINE Abstract. This paper discusses plane symmetry groups, also known as pla- nar crystallographic groups or wallpaper groups. The seventeen unique plane symmetry groups describe the symmetries found in two-dimensional patterns such as those found on weaving patterns, the work of the artist M.C. Escher, and of course wallpaper. We shall discuss the fundamental components and properties of plane symmetry groups. Contents 1. What are Plane Symmetry Groups? 1 2. The Lattice 2 3. The Components of Plane Symmetry Groups 3 4. Generating Regions 5 5. The Crystallographic Restriction 6 6. Some Illustrated Examples 7 References 8 1. What are Plane Symmetry Groups? Since plane symmetry groups basically describe two-dimensional images, it is necessary to make sense of how such images can have isometries. An isometry is commonly understood as a distance- and shape-preserving map, but we must define isometries for this new context. 2 Definition 1.1. A planar image is a function Φ: R −! fc1; : : : ; cng where c1 ··· cn are colors. Note that we must make a distinction between a planar image and an image of a function. Definition 1.2. An isometry of a planar image Φ is an isometry f : R2 −! R2 such that 8~x 2 R2; Φ(f(~x)) = Φ(~x). Definition 1.3. A translation in the plane is a function T : ~x −! ~x + ~v where ~v is a vector in the plane. Two translations T1 : ~x −! ~x + ~v1 and T2 : ~x −! ~x + ~v2 are linearly independent n if ~v1 and ~v2 are linearly independent.
    [Show full text]
  • 1. Math Olympiad Dark Arts
    Preface In A Mathematical Olympiad Primer , Geoff Smith described the technique of inversion as a ‘dark art’. It is difficult to define precisely what is meant by this phrase, although a suitable definition is ‘an advanced technique, which can offer considerable advantage in solving certain problems’. These ideas are not usually taught in schools, mainstream olympiad textbooks or even IMO training camps. One case example is projective geometry, which does not feature in great detail in either Plane Euclidean Geometry or Crossing the Bridge , two of the most comprehensive and respected British olympiad geometry books. In this volume, I have attempted to amass an arsenal of the more obscure and interesting techniques for problem solving, together with a plethora of problems (from various sources, including many of the extant mathematical olympiads) for you to practice these techniques in conjunction with your own problem-solving abilities. Indeed, the majority of theorems are left as exercises to the reader, with solutions included at the end of each chapter. Each problem should take between 1 and 90 minutes, depending on the difficulty. The book is not exclusively aimed at contestants in mathematical olympiads; it is hoped that anyone sufficiently interested would find this an enjoyable and informative read. All areas of mathematics are interconnected, so some chapters build on ideas explored in earlier chapters. However, in order to make this book intelligible, it was necessary to order them in such a way that no knowledge is required of ideas explored in later chapters! Hence, there is what is known as a partial order imposed on the book.
    [Show full text]
  • The Early History of the Metazoa—A Paleontologist's Viewpoint
    ISSN 20790864, Biology Bulletin Reviews, 2015, Vol. 5, No. 5, pp. 415–461. © Pleiades Publishing, Ltd., 2015. Original Russian Text © A.Yu. Zhuravlev, 2014, published in Zhurnal Obshchei Biologii, 2014, Vol. 75, No. 6, pp. 411–465. The Early History of the Metazoa—a Paleontologist’s Viewpoint A. Yu. Zhuravlev Geological Institute, Russian Academy of Sciences, per. Pyzhevsky 7, Moscow, 7119017 Russia email: [email protected] Received January 21, 2014 Abstract—Successful molecular biology, which led to the revision of fundamental views on the relationships and evolutionary pathways of major groups (“phyla”) of multicellular animals, has been much more appre ciated by paleontologists than by zoologists. This is not surprising, because it is the fossil record that provides evidence for the hypotheses of molecular biology. The fossil record suggests that the different “phyla” now united in the Ecdysozoa, which comprises arthropods, onychophorans, tardigrades, priapulids, and nemato morphs, include a number of transitional forms that became extinct in the early Palaeozoic. The morphology of these organisms agrees entirely with that of the hypothetical ancestral forms reconstructed based on onto genetic studies. No intermediates, even tentative ones, between arthropods and annelids are found in the fos sil record. The study of the earliest Deuterostomia, the only branch of the Bilateria agreed on by all biological disciplines, gives insight into their early evolutionary history, suggesting the existence of motile bilaterally symmetrical forms at the dawn of chordates, hemichordates, and echinoderms. Interpretation of the early history of the Lophotrochozoa is even more difficult because, in contrast to other bilaterians, their oldest fos sils are preserved only as mineralized skeletons.
    [Show full text]
  • 10.6 Geometric Symmetry and Tessellations Recall: Two Polygons Were Similar If the Angles Were the Same but the Sides Were Proportional
    10.6 Geometric Symmetry and Tessellations Recall: Two polygons were similar if the angles were the same but the sides were proportional. We could think of taking the first polygon, moving it, rotating it, and scaling it. A rigid motion is an action of only moving and rotating an object, without changing its shape. An object has symmetry if you get the same object back after a rigid motion. Pop quiz!!! How many rigid motions can you find which are symmetries for this object? To study the possible symmetries an object can have, we need to know the types of rigid motions possible. Rigid Motions © 2010 Pearson Education, Inc. All rights reserved. Section 10.6, Slide 8 To reflect an object, you need a mirror (axis of reflection) that you are reflecting across. Notice that the distance of a point and its mirror image are the same distance from the line. Also, lines connecting corresponding points are perpendicular to the axis of reflection. Pop quiz!!! The following is not a rigid motion: 1) reflection 2) translation 3) symmetry 4) rotation 5) glide reflection Rigid Motions • Example: Reflect polygon ABCDE about the axis of reflection l. (continued on next slide) © 2010 Pearson Education, Inc. All rights reserved. Section 10.6, Slide 12 Rigid Motions 2nd: Draw segments BB', CC', DD', and EE', similar to AA'. (continued on next slide) © 2010 Pearson Education, Inc. All rights reserved. Section 10.6, Slide 13 Rigid Motions 3rd: Draw the reflected polygon by connecting vertices A', B', C', D', and E'. © 2010 Pearson Education, Inc.
    [Show full text]
  • Glide Reflection and Other Combined Transformations
    BRIDGES Mathematical Connections· in Art, Music, and Science Glide Reflection and other Combined Transformations Rinus Roelofs Sculptor Lansinkweg 28 7553AL Hengelo The Netherlands E-mail: [email protected] www.rinusroelofs.nl Abstract Glide Reflection is one of the four (translation, rotation, reflection and glide reflection) syrnmetrie transformations we use to classify· the regular divisions of the plane. In a way glide reflection is somewhat different from the other three, because it's not a simple tranformation. lin fact it is a combination of two transformations: translation and reflection. A combination of two but used as a single combined transformation. This article is about my work with of other combinations of transformations that could be used as a combined transformation and how these transformations could be used in the design of patterns and objects. I define three other tranformation which will be explained in the article. The transformations are not restricted to the 2D plane, but are used in the 3D space. Most of the examples are 3D objects or designs. 1. What is Glide Reflection 1. Glide Reflection. First let's have a closer look at Glide Reflection. Maybe one of the most well known examples is M.e. Escher's Horseman (Figure 1) [1]. The shapes of the light and dark horseman are the same apart from the operation of reflection. If you want to place a tile of a light horseman on a tile of a dark horseman, you can't do that with just reflection, rotation or translation. You have to use both translation and reflection. These two transformations have to be used together (Figure 2, 3, 4).
    [Show full text]
  • Planar Symmetries
    34012_CH06_WEB_4632.qxd 4/12/06 4:17 PM Page 6-1 © Jones and Bartlett Publishers. NOT FOR SALE OR DISTRIBUTION Chapter 6 Planar Symmetries 6.1 Introduction The use of symmetry as an aspect of art goes back several millennia, and some early samples of artistic creations into which symmetry was consciously incorporated are displayed in Figure 6.1. The Greek mathematician Euclid (circa 300 BC), whose opus The Elements codified geometry for the following 2000 years, incorporated into this series of 13 books many propositions regarding both two- and three-dimensional symmetric figures. Interestingly, the first proposition of the first book concerns the construction of equilateral triangles and the last book is devoted to the description of the five regular solids (Fig. 7.1), all highly symmetric geometric objects. This endowed Euclid’s work with a symmetry of its own. Given that he could have developed the subject matter in many other ways, it is arguable that this symmetric format was a result of a conscious decision on his part. Euclid and his successors viewed symmetries as merely aesthetically pleasing aspects of geometric objects rather than the subjects of mathematical investigations. In other words, the symmetries of these figures attracted their attention, but their technical investigations were restricted to the mathematical consequences of these symmetries rather than the symmetries themselves. It was not until the 18th century that mathematicians realized that symmetries per se could and should be subject to mathematical research. Since then, the mathematical study of symmetry, better known as group theory, has evolved into a deep and essential branch of mathematics with important applications to the physical sciences.
    [Show full text]
  • Isometries in Three Space and the Seven Solid Crystal Systems
    California State University, San Bernardino CSUSB ScholarWorks Theses Digitization Project John M. Pfau Library 1995 Isometries in three space and the seven solid crystal systems Iris Magee Follow this and additional works at: https://scholarworks.lib.csusb.edu/etd-project Part of the Mathematics Commons Recommended Citation Magee, Iris, "Isometries in three space and the seven solid crystal systems" (1995). Theses Digitization Project. 1110. https://scholarworks.lib.csusb.edu/etd-project/1110 This Project is brought to you for free and open access by the John M. Pfau Library at CSUSB ScholarWorks. It has been accepted for inclusion in Theses Digitization Project by an authorized administrator of CSUSB ScholarWorks. For more information, please contact [email protected]. ISOMETRIES IN THE SEVEN SOLID CRYSTAL SYSTEMS A Project ■. Presented to the Faculty of Galifornia State University, Sari Bernardino in Partial Fulfillment of the Reguirements for the Degree Master of Arts ^,in':;^: . ­ Mathematics Iris Magee September 1995 ISOMETRIES IN THREE SPACE AND THE SEVEN SOLID CRYSTAL SYSTEMS A Project Presented to the California state University, V San Bernardino by Iris Magee September 1995 Approved by: DrVJoan T* Hallett, Chair, Mathematics D te riffin Dr.Peter D. Williams .ABSTRACT ■; My project is exppsitpry on crystallographic groups. T look at the isometries of three spaced with my main concentration on both direct and opposite isometries of finite order. I show that isometries are described by products of reflections. The introduction of regular polyhedra and their rotations will also be included in this review of direct finite isometries. Iprove that the number of orbits of the direct finite isometries must be 2 or 3.
    [Show full text]
  • Chapter 11: the Mathematics of Symmetry
    11/18/2013 Symmetry As are many other core concepts, symmetry is rather Chapter 11: hard to define, and we will not even attempt a proper definition until Section 11.6. We will start our The Mathematics discussion with just an informal stab at the of Symmetry mathematical (or geometric if you prefer) interpretation of symmetry. 11.1 Rigid Motions CopyrightCopyright © © 20142010 Pearson Pearson Education, Education. Inc. All rights reserved. Excursions in Modern Mathematics,11.1-2 7e: 1.1 - 2 Example 11.1 Symmetries of a Triangle Example 11.1 Symmetries of a Triangle The figure shows three triangles: (a) a scalene triangle Even without a formal understanding of what symmetry (all three sides are different), (b) an isosceles triangle, is, most people would answer that the equilateral and (c) an equilateral triangle. In terms of symmetry, triangle in (c) is the most symmetric and the scalene how do these triangles differ? Which one is the most triangle in (a) is the least symmetric. This is in fact symmetric? Least symmetric? correct, but why? CopyrightCopyright © © 20142010 Pearson Pearson Education, Education. Inc. All rights reserved. Excursions in Modern Mathematics,11.1-3 7e: 1.1 - 3 CopyrightCopyright © © 20142010 Pearson Pearson Education, Education. Inc. All rights reserved. Excursions in Modern Mathematics,11.1-4 7e: 1.1 - 4 Example 11.1 Symmetries of a Triangle Example 11.1 Symmetries of a Triangle Think of an imaginary observer–say a tiny (but very In the case of the isosceles triangle (b), the view from observant) ant–standing at the vertices of each of the vertices B and C is the same, but the view from vertex A triangles, looking toward the opposite side.
    [Show full text]
  • Math 3230 Abstract Algebra I Section 1.2 Groups in Science, Art, and Mathematics
    Math 3230 Abstract Algebra I Section 1.2 Groups in science, art, and mathematics Slides created by M. Macauley, Clemson (Modified by E. Gunawan, UConn) http://egunawan.github.io/algebra Fall 2019 1 / 19 Applications of groups We will see applications of group theory in 3 areas: 1. Science 2. Art 3. Mathematics Our choice of examples is influenced by how well they illustrate the material rather than how useful they are. 2 / 19 Groups of symmetries Intuitively, something is symmetrical when it looks the same from more than one point of view. Can you think of an object that exhibits symmetry? The examples of groups that we've seen so far deal with arrangements of similar things. We will see the following fact later. Cayley's Theorem Every group can be viewed as a collection of ways to rearrange some set of things. 3 / 19 How to make a group out of symmetries Groups relate to symmetry because an object's symmetries can be described using arrangements of the object's parts. The following algorithm tells us how to construct a group that describes (or measures) a physical object's symmetry. Algorithm 1. Identify all the parts of the object that are similar (e.g., the corners of an n-gon), and give each such part a different number. 2. Consider the actions that may rearrange the numbered parts, but leave the object in the same physical space. (This collection of actions forms a group.) 3. If you want to visualize the group, explore and map it as we did in the previous lecture with the rectangle puzzle, etc.
    [Show full text]
  • Symmetry, Design and Patterns
    Symmetry, Design, and Patterns Billy Ray Williams Introduction This first part of the unit is meant to introduce the teacher to the subject and vocabulary of the symmetry. The unit will include three activities that the teacher and students can involve themselves in over a two-week period for an hour each day in the classroom culminating in a class field trip. This unit is geared for middle school students, but can be adapted for elementary school students with some modification. Part of the unit will include hands-on activities, such as using ClarisWorks to design and color forms of symmetry. Students are asked to create shapes in ClarisWorks program, work area of Drawing to test a pattern and design for symmetry. The approach for this curriculum unit is interdisciplinary: combining math, fine art, computer, and science. Included in the units will be a pre-reading of symmetry from early-recorded history to present day. We will attempt to answer is there symmetry in chaos? How can symmetry be seen where none seems to exit? “Where is Symmetry in Cultures Found?” – Unit Goals The goal I have is for the students to develop an awareness of finding symmetry in their environment. Students will also develop an understanding of the different types of symmetry. A transformation is a one-to-one mapping on a set of points. Symmetry is said to exist if an object or figure looks the same under a transformation. Types of symmetries are rotational symmetry, reflection symmetry, translation symmetry, and glide reflection symmetry. These four types of symmetries are examples of different types of symmetry on a flat surface called planar symmetry.
    [Show full text]
  • Chapter 19 Symmetry and Patterns
    Chapter 19 Symmetry and Patterns Chapter Objectives Check off these skills when you feel that you have mastered them. F List the first ten terms of the Fibonacci sequence. F Beginning with the number 3, form a ratio of each term in the Fibonacci sequence with its next consecutive term and simplify the ratio; then identify the number that these ratios approximate. F List the numerical ratio for the golden section. F Name and define the four transformations (rigid motions) in the plane. F Analyze a given rosette pattern and determine whether it is dihedral or cyclic. F Given a rosette pattern, determine which rotations preserve it. F Analyze a given strip pattern by determining which transformations produced it. Guided Reading Introduction We study certain numerical and geometric patterns of growth and structure that can be used to model or describe an amazing variety of phenomena in mathematics and science, art, and nature. The mathematical ideas the Fibonacci sequence leads to, such as the golden ratio, spirals, and selfsimilar curves, have long been appreciated for their charm and beauty; but no one can really explain why they are echoed so clearly in the world of art and nature. The properties of selfsimilarity, and reflective and rotational symmetry are ubiquitous in the natural world and are at the core of our ideas of science and art. ³ Key idea Plants exhibiting phyllotaxis have a number of spiral forms coming from a special sequence of numbers. Certain plants have spirals that are geometrically similar to one another. The spirals are arranged in a regular way, with balance and “proportion”.
    [Show full text]