The Mathematics of the Rubik's Cube
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GROUP ACTIONS 1. Introduction the Groups Sn, An, and (For N ≥ 3)
GROUP ACTIONS KEITH CONRAD 1. Introduction The groups Sn, An, and (for n ≥ 3) Dn behave, by their definitions, as permutations on certain sets. The groups Sn and An both permute the set f1; 2; : : : ; ng and Dn can be considered as a group of permutations of a regular n-gon, or even just of its n vertices, since rigid motions of the vertices determine where the rest of the n-gon goes. If we label the vertices of the n-gon in a definite manner by the numbers from 1 to n then we can view Dn as a subgroup of Sn. For instance, the labeling of the square below lets us regard the 90 degree counterclockwise rotation r in D4 as (1234) and the reflection s across the horizontal line bisecting the square as (24). The rest of the elements of D4, as permutations of the vertices, are in the table below the square. 2 3 1 4 1 r r2 r3 s rs r2s r3s (1) (1234) (13)(24) (1432) (24) (12)(34) (13) (14)(23) If we label the vertices in a different way (e.g., swap the labels 1 and 2), we turn the elements of D4 into a different subgroup of S4. More abstractly, if we are given a set X (not necessarily the set of vertices of a square), then the set Sym(X) of all permutations of X is a group under composition, and the subgroup Alt(X) of even permutations of X is a group under composition. If we list the elements of X in a definite order, say as X = fx1; : : : ; xng, then we can think about Sym(X) as Sn and Alt(X) as An, but a listing in a different order leads to different identifications 1 of Sym(X) with Sn and Alt(X) with An. -
Mathematics of the Rubik's Cube
Mathematics of the Rubik's cube Associate Professor W. D. Joyner Spring Semester, 1996{7 2 \By and large it is uniformly true that in mathematics that there is a time lapse between a mathematical discovery and the moment it becomes useful; and that this lapse can be anything from 30 to 100 years, in some cases even more; and that the whole system seems to function without any direction, without any reference to usefulness, and without any desire to do things which are useful." John von Neumann COLLECTED WORKS, VI, p. 489 For more mathematical quotes, see the first page of each chapter below, [M], [S] or the www page at http://math.furman.edu/~mwoodard/mquot. html 3 \There are some things which cannot be learned quickly, and time, which is all we have, must be paid heavily for their acquiring. They are the very simplest things, and because it takes a man's life to know them the little new that each man gets from life is very costly and the only heritage he has to leave." Ernest Hemingway (From A. E. Hotchner, PAPA HEMMINGWAY, Random House, NY, 1966) 4 Contents 0 Introduction 13 1 Logic and sets 15 1.1 Logic................................ 15 1.1.1 Expressing an everyday sentence symbolically..... 18 1.2 Sets................................ 19 2 Functions, matrices, relations and counting 23 2.1 Functions............................. 23 2.2 Functions on vectors....................... 28 2.2.1 History........................... 28 2.2.2 3 × 3 matrices....................... 29 2.2.3 Matrix multiplication, inverses.............. 30 2.2.4 Muliplication and inverses............... -
The Observability of the Fibonacci and the Lucas Cubes
View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Elsevier - Publisher Connector Discrete Mathematics 255 (2002) 55–63 www.elsevier.com/locate/disc The observability of the Fibonacci and the Lucas cubes Ernesto DedÃo∗;1, Damiano Torri1, Norma Zagaglia Salvi1 Dipartimento di Matematica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy Received 5 April 1999; received inrevised form 31 July 2000; accepted 8 January2001 Abstract The Fibonacci cube n is the graph whose vertices are binary strings of length n without two consecutive 1’s and two vertices are adjacent when their Hamming distance is exactly 1. If the binary strings do not contain two consecutive 1’s nora1intheÿrst and in the last position, we obtainthe Lucas cube Ln. We prove that the observability of n and Ln is n, where the observability of a graph G is the minimum number of colors to be assigned to the edges of G so that the coloring is proper and the vertices are distinguished by their color sets. c 2002 Elsevier Science B.V. All rights reserved. MSC: 05C15; 05A15 Keywords: Fibonacci cube; Fibonacci number; Lucas number; Observability 1. Introduction A Fibonacci string of order n is a binary string of length n without two con- secutive ones. Let and ÿ be binary strings; then ÿ denotes the string obtained by concatenating and ÿ. More generally, if S is a set of strings, then Sÿ = {ÿ: ∈ S}. If Cn denotes the set of the Fibonacci strings of order n, then Cn+2 =0Cn+1 +10Cn and |Cn| = Fn, where Fn is the nth Fibonacci number. -
On Hardy's Apology Numbers
ON HARDY’S APOLOGY NUMBERS HENK KOPPELAAR AND PEYMAN NASEHPOUR Abstract. Twelve well known ‘Recreational’ numbers are generalized and classified in three generalized types Hardy, Dudeney, and Wells. A novel proof method to limit the search for the numbers is exemplified for each of the types. Combinatorial operators are defined to ease programming the search. 0. Introduction “Recreational Mathematics” is a broad term that covers many different areas including games, puzzles, magic, art, and more [31]. Some may have the impres- sion that topics discussed in recreational mathematics in general and recreational number theory, in particular, are only for entertainment and may not have an ap- plication in mathematics, engineering, or science. As for the mathematics, even the simplest operation in this paper, i.e. the sum of digits function, has application outside number theory in the domain of combinatorics [13, 26, 27, 28, 34] and in a seemingly unrelated mathematical knowledge domain: topology [21, 23, 15]. Pa- pers about generalizations of the sum of digits function are discussed by Stolarsky [38]. It also is a surprise to see that another topic of this paper, i.e. Armstrong numbers, has applications in “data security” [16]. In number theory, functions are usually non-continuous. This inhibits solving equations, for instance, by application of the contraction mapping principle because the latter is normally for continuous functions. Based on this argument, questions about solving number-theoretic equations ramify to the following: (1) Are there any solutions to an equation? (2) If there are any solutions to an equation, then are finitely many solutions? (3) Can all solutions be found in theory? (4) Can one in practice compute a full list of solutions? arXiv:2008.08187v1 [math.NT] 18 Aug 2020 The main purpose of this paper is to investigate these constructive (or algorith- mic) problems by the fixed points of some special functions of the form f : N N. -
Figurate Numbers
Figurate Numbers by George Jelliss June 2008 with additions November 2008 Visualisation of Numbers The visual representation of the number of elements in a set by an array of small counters or other standard tally marks is still seen in the symbols on dominoes or playing cards, and in Roman numerals. The word "calculus" originally meant a small pebble used to calculate. Bear with me while we begin with a few elementary observations. Any number, n greater than 1, can be represented by a linear arrangement of n counters. The cases of 1 or 0 counters can be regarded as trivial or degenerate linear arrangements. The counters that make up a number m can alternatively be grouped in pairs instead of ones, and we find there are two cases, m = 2.n or 2.n + 1 (where the dot denotes multiplication). Numbers of these two forms are of course known as even and odd respectively. An even number is the sum of two equal numbers, n+n = 2.n. An odd number is the sum of two successive numbers 2.n + 1 = n + (n+1). The even and odd numbers alternate. Figure 1. Representation of numbers by rows of counters, and of even and odd numbers by various, mainly symmetric, formations. The right-angled (L-shaped) formation of the odd numbers is known as a gnomon. These do not of course exhaust the possibilities. 1 2 3 4 5 6 7 8 9 n 2 4 6 8 10 12 14 2.n 1 3 5 7 9 11 13 15 2.n + 1 Triples, Quadruples and Other Forms Generalising the divison into even and odd numbers, the counters making up a number can of course also be grouped in threes or fours or indeed any nonzero number k. -
An Algebraic Approach to the Weyl Groupoid
An Algebraic Approach to the Weyl Groupoid Tristan Bice✩ Institute of Mathematics Czech Academy of Sciences Zitn´a25,ˇ 115 67 Prague, Czech Republic Abstract We unify the Kumjian-Renault Weyl groupoid construction with the Lawson- Lenz version of Exel’s tight groupoid construction. We do this by utilising only a weak algebraic fragment of the C*-algebra structure, namely its *-semigroup reduct. Fundamental properties like local compactness are also shown to remain valid in general classes of *-rings. Keywords: Weyl groupoid, tight groupoid, C*-algebra, inverse semigroup, *-semigroup, *-ring 2010 MSC: 06F05, 20M25, 20M30, 22A22, 46L05, 46L85, 47D03 1. Introduction 1.1. Background Renault’s groundbreaking thesis [Ren80] revealed the striking interplay be- tween ´etale groupoids and the C*-algebras they give rise to. Roughly speaking, the ´etale groupoid provides a more topological picture of the corresponding C*-algebra, with various key properties of the algebra, like nuclearity and sim- plicity (see [ADR00] and [CEP+19]), being determined in a straightforward way from the underlying ´etale groupoid. Naturally, this has led to the quest to find appropriate ´etale groupoid models for various C*-algebras. Two general methods have emerged for finding such models, namely arXiv:1911.08812v3 [math.OA] 20 Sep 2020 1. Exel’s tight groupoid construction from an inverse semigroup, and 2. Kumjian-Renault’s Weyl groupoid construction from a Cartan C*-subalgebra (see [Exe08], [Kum86] and [Ren08]). However, both of these have their limi- tations. For example, tight groupoids are always ample, which means the cor- responding C*-algebras always have lots of projections. On the other hand, the Weyl groupoid is always effective, which discounts many naturally arising groupoids. -
A Class of Totally Geodesic Foliations of Lie Groups
Proc. Indian Acad. Sci. (Math. Sci.), Vol. 100, No. 1, April 1990, pp. 57-64. ~2 Printed in India. A class of totally geodesic foliations of Lie groups G SANTHANAM School of Mathematics. Tata Institute of Fundamental Research, Homi Bhabha Road, Bombay 400005, India MS received 4 October 1988; revised 25 May 1989 A~traet. This paper is devoted to classifying the foliations of G with leaves of the form .qKh - t where G is a compact, connected and simply connected L,c group and K is a connected closed subgroup of G such that G/K is a rank-I Riemannian symmetric space. In the case when G/K =S", the homotopy type of space of such foliations is also given. Keywords. Foliations; rank-I Riemannian symmetric space; cutlocus. I. Introduction The study of fibrations of spheres by great spheres is a very interesting problem in geometry and it is very important in the theory of Blaschke manifolds. In [l], Gluck and Warner have studied the great circle fibrations of the three spheres. In that paper they have proved very interesting results. When we look at the problem group theoretically, we see that all the results of [1] go through, for foliations of G with leaves of the form gKh- 1 where G is a compact, connected and simply connected Lie group and K is a connected closed subgroup of G such that G/K is a rank- l Riemannian symmetric space (see [-2]), except perhaps the theorem 3 for the pair (G, K) such that G/K=CP n, HP ~ etc. -
Fibonacci's Perfect Spiral
Middle School Fibonacci's Perfect Spiral This l esson was created to combine math history, math, critical thinking, and art. Students will l earn about Fibonacci, the code he created, and how the Fibonacci sequence relates to real l ife and the perfect spiral. Students will practice drawing perfect spirals and l earn how patterns are a mathematical concept that surrounds us i n real l ife. This l esson i s designed to take 3 to 4 class periods of 45 minutes each, depending on the students’ focus and depth of detail i n the assignments. Common Core CCSS.MATH.CONTENT.HSF.IF.A.3 Recognize that Standards: sequences are functions, sometimes defined recursively, whose domain i s a subset of the i ntegers. For example, the Fibonacci sequence i s defined recursively by f(0) = f(1) = 1, f(n+1) = f(n) + f(n1) for n ≥ 1. CCSS.MATH.CONTENT.7.EE.B.4 Use variables to represent quantities i n a realworld or mathematical problem, and construct simple equations and inequalities to solve problems by reasoning about the quantities. CCSS.MATH.CONTENT.7.G.A.1 Solve problems involving scale drawings of geometric figures, i ncluding computing actual l engths and areas from a scale drawing and reproducing a scale drawing at a different scale. CCSS.MATH.CONTENT.7.G.A.2 Draw (freehand, with ruler and protractor, and with technology) geometric shapes with given conditions. CCSS.MATH.CONTENT.8.G.A.2 Understand that a twodimensional figure i s congruent to another i f the second can be obtained from the first by a sequence of rotations, reflections, and translations; given two congruent figures, describe a sequence that exhibits the congruence between them. -
Distortion of Dimension by Metric Space-Valued Sobolev Mappings Lecture II
Distortion of dimension by metric space-valued Sobolev mappings Lecture II Jeremy Tyson University of Illinois at Urbana-Champaign Metric Spaces: Analysis, Embeddings into Banach Spaces, Applications Texas A&M University College Station, TX 8 July 2016 Outline Lecture I. Sobolev and quasiconformal mappings in Euclidean space Lecture II. Sobolev mappings between metric spaces Lecture III. Dimension distortion theorems for Sobolev and quasiconformal mappings defined from the sub-Riemannian Heisenberg group f homeo in Rn, n ≥ 2 Gehring metric QC ) analytic QC ) geometric QC modulus) estimates (local) QS f : X ! Y homeo between proper Q-regular mms satisfying Q-PI, Q > 1 0 metric QC HK=)98 QS f : X ! Y homeo between proper Q-regular mms 0 . geometric QC T(98 QS Motivation: quasiconformal mappings in metric spaces The theory of analysis in metric measure spaces originates in two papers of Juha Heinonen and Pekka Koskela: ‘Definitions of quasiconformality', Invent. Math., 1995 `QC maps in metric spaces of controlled geometry', Acta Math., 1998 The latter paper introduced the concept of p-Poincar´einequality on a metric measure space, which has become the standard axiom for first-order analysis. f : X ! Y homeo between proper Q-regular mms satisfying Q-PI, Q > 1 0 metric QC HK=)98 QS f : X ! Y homeo between proper Q-regular mms 0 . geometric QC T(98 QS Motivation: quasiconformal mappings in metric spaces The theory of analysis in metric measure spaces originates in two papers of Juha Heinonen and Pekka Koskela: ‘Definitions of quasiconformality', Invent. Math., 1995 `QC maps in metric spaces of controlled geometry', Acta Math., 1998 The latter paper introduced the concept of p-Poincar´einequality on a metric measure space, which has become the standard axiom for first-order analysis. -
Graphs of Groups: Word Computations and Free Crossed Resolutions
Graphs of Groups: Word Computations and Free Crossed Resolutions Emma Jane Moore November 2000 Summary i Acknowledgements I would like to thank my supervisors, Prof. Ronnie Brown and Dr. Chris Wensley, for their support and guidance over the past three years. I am also grateful to Prof. Tim Porter for helpful discussions on category theory. Many thanks to my family and friends for their support and encouragement and to all the staff and students at the School of Mathematics with whom I had the pleasure of working. Finally thanks to EPSRC who paid my fees and supported me financially. ii Contents Introduction 1 1 Groupoids 4 1.1 Graphs, Categories, and Groupoids .................... 4 1.1.1 Graphs ................................ 5 1.1.2 Categories and Groupoids ..................... 6 1.2 Groups to Groupoids ............................ 12 1.2.1 Examples and Properties of Groupoids .............. 12 1.2.2 Free Groupoid and Words ..................... 15 1.2.3 Normal Subgroupoids and Quotient Groupoids .......... 17 1.2.4 Groupoid Cosets and Transversals ................. 18 1.2.5 Universal Groupoids ........................ 20 1.2.6 Groupoid Pushouts and Presentations .............. 24 2 Graphs of Groups and Normal Forms 29 2.1 Fundamental Groupoid of a Graph of Groups .............. 29 2.1.1 Graph of Groups .......................... 30 2.1.2 Fundamental Groupoid ....................... 31 2.1.3 Fundamental Group ........................ 34 2.1.4 Normal Form ............................ 35 2.1.5 Examples .............................. 41 2.1.6 Graph of Groupoids ........................ 47 2.2 Implementation ............................... 49 2.2.1 Normal Form and Knuth Bendix Methods ............ 50 iii 2.2.2 Implementation and GAP4 Output ................ 54 3 Total Groupoids and Total Spaces 61 3.1 Cylinders ................................. -
Regular Representations and Coset Representations Combined with a Mirror-Permutation
MATCH MATCH Commun. Math. Comput. Chem. 83 (2020) 65-84 Communications in Mathematical and in Computer Chemistry ISSN 0340 - 6253 Regular Representations and Coset Representations Combined with a Mirror-Permutation. Concordant Construction of the Mark Table and the USCI-CF Table of the Point Group Td Shinsaku Fujita Shonan Institute of Chemoinformatics and Mathematical Chemistry, Kaneko 479-7 Ooimachi, Ashigara-Kami-Gun, Kanagawa-Ken, 258-0019 Japan [email protected] (Received November 21, 2018) Abstract A combined-permutation representation (CPR) of degree 26 (= 24 + 2) for a regular representation (RR) of degree 24 is derived algebraically from a multiplica- tion table of the point group Td, where reflections are explicitly considered in the form of a mirror-permutation of degree 2. Thereby, the standard mark table and the standard USCI-CF table (unit-subduced-cycle-index-with-chirality-fittingness table) are concordantly generated by using the GAP functions MarkTableforUSCI and constructUSCITable, which have been developed by Fujita for the purpose of systematizing the concordant construction. A CPR for each coset representation (CR) (Gin)Td is obtained algebraically by means of the GAP function CosetRepCF developed by Fujita (Appendix A). On the other hand, CPRs for CRs are obtained geometrically as permutation groups by considering appropriate skeletons, where the point group Td acts on an orbit of jTdj=jGij positions to be equivalent in a given skeleton so as to generate the CPR of degree jTdj=jGij. An RR as a CPR is obtained by considering a regular body (RB), the jTdj positions of which are considered to be governed by RR (C1n)Td. -
Student Task Statements (8.7.B.3)
GRADE 8 MATHEMATICS BY NAME DATE PERIOD Unit 7, Lesson 3: Powers of Powers of 10 Let's look at powers of powers of 10. 3.1: Big Cube What is the volume of a giant cube that measures 10,000 km on each side? 3.2: Taking Powers of Powers of 10 1. a. Complete the table to explore patterns in the exponents when raising a power of 10 to a power. You may skip a single box in the table, but if you do, be prepared to explain why you skipped it. expression expanded single power of 10 b. If you chose to skip one entry in the table, which entry did you skip? Why? 2. Use the patterns you found in the table to rewrite as an equivalent expression with a single exponent, like . GRADE 8 MATHEMATICS BY NAME DATE PERIOD 3. If you took the amount of oil consumed in 2 months in 2013 worldwide, you could make a cube of oil that measures meters on each side. How many cubic meters of oil is this? Do you think this would be enough to fill a pond, a lake, or an ocean? 3.3: How Do the Rules Work? Andre and Elena want to write with a single exponent. • Andre says, “When you multiply powers with the same base, it just means you add the exponents, so .” • Elena says, “ is multiplied by itself 3 times, so .” Do you agree with either of them? Explain your reasoning. Are you ready for more? . How many other whole numbers can you raise to a power and get 4,096? Explain or show your reasoning.