Towards the Classification of Finite Simple Groups with Exactly Three
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On Some Generation Methods of Finite Simple Groups
Introduction Preliminaries Special Kind of Generation of Finite Simple Groups The Bibliography On Some Generation Methods of Finite Simple Groups Ayoub B. M. Basheer Department of Mathematical Sciences, North-West University (Mafikeng), P Bag X2046, Mmabatho 2735, South Africa Groups St Andrews 2017 in Birmingham, School of Mathematics, University of Birmingham, United Kingdom 11th of August 2017 Ayoub Basheer, North-West University, South Africa Groups St Andrews 2017 Talk in Birmingham Introduction Preliminaries Special Kind of Generation of Finite Simple Groups The Bibliography Abstract In this talk we consider some methods of generating finite simple groups with the focus on ranks of classes, (p; q; r)-generation and spread (exact) of finite simple groups. We show some examples of results that were established by the author and his supervisor, Professor J. Moori on generations of some finite simple groups. Ayoub Basheer, North-West University, South Africa Groups St Andrews 2017 Talk in Birmingham Introduction Preliminaries Special Kind of Generation of Finite Simple Groups The Bibliography Introduction Generation of finite groups by suitable subsets is of great interest and has many applications to groups and their representations. For example, Di Martino and et al. [39] established a useful connection between generation of groups by conjugate elements and the existence of elements representable by almost cyclic matrices. Their motivation was to study irreducible projective representations of the sporadic simple groups. In view of applications, it is often important to exhibit generating pairs of some special kind, such as generators carrying a geometric meaning, generators of some prescribed order, generators that offer an economical presentation of the group. -
Finite Groups, Designs and Codes
Abstract Introduction Terminology and notation Group Actions and Permutation Characters Method 1 References Finite Groups, Designs and Codes J Moori School of Mathematical Sciences, University of KwaZulu-Natal Pietermaritzburg 3209, South Africa ASI, Opatija, 31 May –11 June 2010 J Moori, ASI 2010, Opatija, Croatia Groups, Designs and Codes Abstract Introduction Terminology and notation Group Actions and Permutation Characters Method 1 References Finite Groups, Designs and Codes J Moori School of Mathematical Sciences, University of KwaZulu-Natal Pietermaritzburg 3209, South Africa ASI, Opatija, 31 May –11 June 2010 J Moori, ASI 2010, Opatija, Croatia Groups, Designs and Codes Abstract Introduction Terminology and notation Group Actions and Permutation Characters Method 1 References Outline 1 Abstract 2 Introduction 3 Terminology and notation 4 Group Actions and Permutation Characters Permutation and Matrix Representations Permutation Characters 5 Method 1 Janko groups J1 and J2 Conway group Co2 6 References J Moori, ASI 2010, Opatija, Croatia Groups, Designs and Codes Abstract Introduction Terminology and notation Group Actions and Permutation Characters Method 1 References Abstract Abstract We will discuss two methods for constructing codes and designs from finite groups (mostly simple finite groups). This is a survey of the collaborative work by the author with J D Key and B Rorigues. In this talk (Talk 1) we first discuss background material and results required from finite groups, permutation groups and representation theory. Then we aim to describe our first method of constructing codes and designs from finite groups. J Moori, ASI 2010, Opatija, Croatia Groups, Designs and Codes Abstract Introduction Terminology and notation Group Actions and Permutation Characters Method 1 References Abstract Abstract We will discuss two methods for constructing codes and designs from finite groups (mostly simple finite groups). -
RIGID LOCAL SYSTEMS with MONODROMY GROUP the CONWAY GROUP Co2
RIGID LOCAL SYSTEMS WITH MONODROMY GROUP THE CONWAY GROUP Co2 NICHOLAS M. KATZ, ANTONIO ROJAS-LEON,´ AND PHAM HUU TIEP Abstract. We first develop some basic facts about hypergeometric sheaves on the multi- plicative group Gm in characteristic p > 0. Certain of their Kummer pullbacks extend to irreducible local systems on the affine line in characteristic p > 0. One of these, of rank 23 in characteristic p = 3, turns out to have the Conway group Co2, in its irreducible orthogonal representation of degree 23, as its arithmetic and geometric monodromy groups. Contents Introduction 1 1. The basic set up, and general results 1 2. The criterion for finite monodromy 10 3. Theorems of finite monodromy 11 4. Determination of the monodromy groups 17 References 18 Introduction In the first two sections, we give the general set up. In the third section, we apply known criteria to show that certain local systems of rank 23 over the affine line in characteristic 3 have finite (arithmetic and geometric) monodromy groups. In the final section, we show that the finite monodromy groups in question are the Conway group Co2 in its 23-dimensional irreducible orthogonal representation. 1. The basic set up, and general results × We fix a prime number p, a prime number ` 6= p, and a nontrivial Q` -valued additive character of Fp. For k=Fp a finite extension, we denote by k the nontrivial additive character of k given by k := ◦ Tracek=Fp . In perhaps more down to earth terms, we fix a × nontrivial Q(µp) -valued additive character of Fp, and a field embedding of Q(µp) into Q` for some ` 6= p. -
The Centre of a Block
THE CENTRE OF A BLOCK A thesis submitted to the University of Manchester for the degree of Doctor of Philosophy in the Faculty of Engineering and Physical Sciences 2016 Inga Schwabrow School of Mathematics 2 Contents Abstract 5 Declaration 7 Copyright Statement 9 Acknowledgements 11 Introduction 13 1 Modular Representation Theory 17 1.1 Basic notation and setup . 17 1.2 Conjugacy class sums, characters and Burnside's formula . 18 1.3 Blocks . 22 1.4 Defect and defect groups . 25 1.5 Jacobson radical and Loewy length . 28 1.6 The Reynolds ideal . 35 2 Equivalences of blocks 37 2.1 Brauer correspondence . 37 2.2 Morita equivalence . 38 2.3 Derived equivalence . 38 2.4 Stable equivalence of Morita type . 40 2.5 Properties of blocks with TI defect groups . 41 2.6 On using the centre to show no derived equivalence exists . 43 3 Blocks with trivial intersection defect groups 44 3 3.1 The Mathieu group M11 with p =3.................... 45 3.2 The McLaughlin group McL, and Aut(McL), with p = 5 . 49 3.3 The Janko group J4 with p =11...................... 52 3.4 The projective special unitary groups . 54 3.5 A question of Rickard . 60 3.6 On the existence of perfect isometries in blocks with TI defect groups . 62 4 On the Loewy length of the Suzuki groups and the small Ree groups in defining characteristic 68 4.1 Relating structure constants . 68 4.2 Suzuki Groups . 70 4.3 The Ree groups . 76 5 More sporadic simple groups 108 5.1 Mathieu groups . -
Jhep07(2019)026
Published for SISSA by Springer Received: January 18, 2019 Revised: May 3, 2019 Accepted: June 26, 2019 Published: July 4, 2019 JHEP07(2019)026 Monster anatomy Jin-Beom Bae, Kimyeong Lee and Sungjay Lee Korea Institute for Advanced Study, 85 Hoegiro, Dongdaemun-Gu, Seoul 02455, Korea E-mail: [email protected], [email protected], [email protected] Abstract: 47 We investigate the two-dimensional conformal field theories (CFTs) of c = 2 , 116 c = 5 and c = 23 `dual' to the critical Ising model, the three state Potts model and the tensor product of two Ising models, respectively. We argue that these CFTs exhibit moonshines for the double covering of the baby Monster group, 2 · B, the triple covering 0 of the largest Fischer group, 3 · Fi24 and multiple-covering of the second largest Conway 1+22 group, 2 · 2 · Co2. Various twined characters are shown to satisfy generalized bilinear relations involving Mckay-Thompson series. We also rediscover that the `self-dual' two- dimensional bosonic conformal field theory of c = 12 has the Conway group Co0 ' 2 · Co1 as an automorphism group. Keywords: Conformal and W Symmetry, Field Theories in Lower Dimensions ArXiv ePrint: 1811.12263 Open Access, c The Authors. https://doi.org/10.1007/JHEP07(2019)026 Article funded by SCOAP3. Contents 1 Introduction1 2 Dual of the Ising model and the Baby Monster3 0 3 Dual of the three-state Potts model and 3 · Fi24 6 2 1+22 4 Dual of the critical Ising and 2 · 2 · Co2 9 JHEP07(2019)026 5 Self-dual RCFT and 2 · Co1 11 6 Discussion 13 A Dimension of the irreducible representations 15 B 0 B Character tables of 2 · and 3 · Fi24 16 C Generalized bilinear relations 18 C.1 2 · B 18 0 C.2 3 · Fi24 18 1 Introduction Mckay and Thompson's remarkable observation between the monster group M and the modular objects, especially, the j-invariant, motivated the study of the so-called `Monstrous Moonshine' in [1]. -
Extended Near Hexagons and Line Systems
Extended near hexagons and line systems Hans Cuypers Department of Mathematics Eindhoven University of Technology P.O. Box 513, 5600 MB Eindhoven The Netherlands email: [email protected] October 2, 2002 Abstract In this paper we study extended near hexagons, and classify a class of line systems in which two lines are either perpendicular, or make an angle α with cos α = 1=3. Among the examples we encounter a set of 2300 lines in R23 ± 24 related to the second Conway group Co2 and a set of 2048 lines in R related 1+11 to the group 2 :M24. The other line systems under consideration in this paper are all subsystems of these. MSC classification: 51E30, 05B99, 51E12, 20D8 Keywords: Extended near hexagons, line systems, spherical designs. 1. Introduction In [34], Shult and Yanushka studied a class of line systems in Rn, equipped with the standard inner product ( ), in which any pair of distinct lines is either per- pendicular or makes an angle· jα · with cos α = 1=3. A nice and simple example of such a line system is the set of 4 lines in R3±passing through the vertices of a regular tetrahedron centered at the origin. Other examples considered by Shult and Yanushka include a system of 2300 lines in R23 related to the Leech lattice and the 24 second Conway group Co2 and a system of 2048 lines in R related to the binary 1+11 Golay code and the group 2 :M24. These line systems are all tetrahedrally closed, i.e., given three lines of the system passing through three of the four vertices of a regular tetrahedron centered at the origin, then also the line passing through the fourth vertex of the tetrahedron is present in the line system. -
CHARACTERS of Π1-DEGREE with CYCLOTOMIC FIELDS of VALUES 1. Introduction in 2006, G. Navarro and P.H. Tiep [NT06] Confirmed
CHARACTERS OF π1-DEGREE WITH CYCLOTOMIC FIELDS OF VALUES EUGENIO GIANNELLI, NGUYEN NGOC HUNG, A. A. SCHAEFFER FRY, AND CAROLINA VALLEJO Abstract. We characterize finite groups that possess a nontrivial irreducible character of tp, qu1-degree with values in Qpe2πi{pq or Qpe2πi{qq, where p and q are primes. This extends previous work of Navarro-Tiep and of Giannelli-Schaeffer Fry-Vallejo. Along the way we completely describe the alternating groups possessing a nontrivial irreducible rational-valued character of tp, qu1-degree. A similar classification is obtained for solvable groups, when p “ 2. 1. Introduction In 2006, G. Navarro and P.H. Tiep [NT06] confirmed a conjecture of R. Gow predicting that every group of even order has a nontrivial rational-valued irreducible character of odd degree. Later, in [NT08], they generalized their result by proving that every finite group of order divisible by a prime q admits a nontrivial irreducible character of q1-degree with values in Qpe2iπ{qq, the cyclotomic field extending the rational numbers by a primitive q-th root of unity. In [GSV19], the first, third, and fourth-named authors have recently shown that for any set π consisting of at most two primes, every nontrivial group has a nontrivial character of π1-degree (that is, a character of p1-degree, for all primes p P π). How to extend these results, if possible, is the main topic under consideration in this article. In Theorem A, we show that every finite group possesses a nontrivial irreducible character of t2, qu1-degree with values in Qpe2iπ{qq, an unexpected result that generalizes both [NT06] and [NT08] in the fashion of [GSV19]. -
Recent Progress in the Symmetric Generation of Groups, to Appear in the Proceedings of the Conference Groups St Andrews 2009 [28] B
RECENT PROGRESS IN THE SYMMETRIC GENERATION OF GROUPS BEN FAIRBAIRN Abstract. Many groups possess highly symmetric generating sets that are naturally endowed with an underlying combinatorial struc- ture. Such generating sets can prove to be extremely useful both theoretically in providing new existence proofs for groups and prac- tically by providing succinct means of representing group elements. We give a survey of results obtained in the study of these symmet- ric generating sets. In keeping with earlier surveys on this matter, we emphasize the sporadic simple groups. ADDENDUM: This is an updated version of a survey article orig- inally accepted for inclusion in the proceedings of the 2009 ‘Groups St Andrews’ conference [27]. Since [27] was accepted the author has become aware of other recent work in the subject that we incorporate to provide an updated version here (the most notable addition being the contents of Section 3.4). 1. Introduction This article is concerned with groups that are generated by highly symmetric subsets of their elements: that is to say by subsets of el- ements whose set normalizer within the group they generate acts on them by conjugation in a highly symmetric manner. Rather than inves- tigate the behaviour of known groups we turn this procedure around and ask what groups can be generated by a set of elements that pos- sesses a certain assigned set of symmetries. This enables constructions arXiv:1004.2272v2 [math.GR] 21 Apr 2010 by hand of a number of interesting groups, including many of the spo- radic simple groups. Much of the emphasis of the research project to date has been concerned with using these techniques to construct spo- radic simple groups, and this article will emphasize this important spe- cial case. -
THE STRONG SYMMETRIC GENUS and GENERALIZED SYMMETRIC GROUPS of TYPE G(N, 3)
THE STRONG SYMMETRIC GENUS AND GENERALIZED SYMMETRIC GROUPS OF TYPE G(n, 3) MICHAEL A. JACKSON Abstract. The generalized symmetric groups are defined to be G(n, m) = Zm o Σn where n, m ∈ Z+. The strong symmetric genus of a finite group G is the smallest genus of a closed orientable topological surface on which G acts faithfully as a group of orientation preserving automorphisms. The present work extends work on the strong symmetric genus by Marston Conder, who studied the symmetric groups, which are G(n, 1), and by the author, who studied the hyperoctahedral groups, which are G(n, 2). We give results for the strong symmetric genus of the groups of type G(n, 3). Grove City College, 100 Campus Drive, Grove City, PA 16127 [email protected]. 1 1. Introduction The strong symmetric genus of the finite group G is the smallest genus of a compact orientable surface on which G acts as a group of orientation preserving symmetries and is denoted σ0(G). The strong symmetric genus has a long history beginning with Burnside [1]. For more general information see [10, Chapter 6]. The strong symmetric genus of many groups are known: the alternating and symmetric groups [2, 3, 4], the hyperoctahedral groups [12], the remaining finite Coxeter groups [11], the groups P SL2(q) [8, 9] and SL2(q) [15], as well as the sporadic finite simple groups [5, 16, 17, 18]. The generalized symmetric groups G(n, m) are defined for n > 1 and m ≥ 1 to be the wreath product Zm o Σn. -
Representation Theoretic Existence Proof for Fischer Group Fi 23
Cornell University Mathematics Department Senior Thesis REPRESENTATION THEORETIC EXISTENCE PROOF FOR FISCHER GROUP Fi23 HYUN KYU KIM May 2008 A thesis presented in partial fulfillment of criteria for Honors in Mathematics Bachelor of Arts, Cornell University Thesis Advisor(s) Gerhard O. Michler Department of Mathematics 1 2 HYUN KYU KIM ABSTRACT In the first section of this senior thesis the author provides some new efficient algorithms for calculating with finite permutation groups. They cannot be found in the computer algebra system Magma, but they can be implemented there. For any finite group G with a given set of generators, the algorithms calculate generators of a fixed subgroup of G as short words in terms of original generators. Another new algorithm provides such a short word for a given element of G. These algo- rithms are very useful for documentation and performing demanding experiments in computational group theory. In the later sections, the author gives a self-contained existence proof for Fis- 18 13 2 cher's sporadic simple group Fi23 of order 2 · 3 · 5 · 7 · 11 · 13 · 17 · 23 using G. Michler's Algorithm [11] constructing finite simple groups from irreducible sub- groups of GLn(2). This sporadic group was originally discovered by B. Fischer in [6] by investigating 3-transposition groups, see also [5]. This thesis gives a representa- tion theoretic and algorithmic existence proof for his group. The author constructs the three non-isomorphic extenstions Ei by the two 11-dimensional non-isomorphic simple modules of the Mathieu group M23 over F = GF(2). In two cases Michler's Algorithm fails. -
The 5-Modular Representations of the Tits Simple Group in the Principal Block
mathematics of computation volume 57,number 195 july 1991,pages 369-386 THE 5-MODULARREPRESENTATIONS OF THE TITS SIMPLE GROUP IN THE PRINCIPAL BLOCK holger w. gollan Abstract. In this paper we show how to construct the 5-modular absolutely irreducible representations of the Tits simple group in the principal block, which is the only block of positive defect. Starting with the smallest nontrivial ones, all the others except one pair are obtained as constituents of tensor products of dimension at most 729. The last two we get from a permutation representation of degree 1600. We give an exact description of the construction of the first one of degree 26 by extending its restrictions to several subgroups, a method first used in the existence proof of the Janko group J4 . Using the explicit matrices obtained from the above constructions, we work out the Green correspondents and sources of all the representations and state their socle series. 0. Introduction One aim of modular representation theory is the construction of the p- modular absolutely irreducible representations of finite groups G, where p is a prime dividing the group order \G\. Having done this, invariants of these representations like vertices, Green correspondents, and sources may be com- puted to get more information about them. This paper deals with the 5-modular representations of the Tits simple group -E4(2)' in the principal block. This is in some sense the only interesting block for this problem in E4(2)', since all the other blocks are blocks of defect 0. The following tables show some small permutation representations and tensor products of E4(2)' written as sums of their 5-modular constituents. -
Centres of Blocks of Finite Groups with Trivial Intersection Sylow $ P
Centres of blocks of finite groups with trivial intersection Sylow p-subgroups Inga Schwabrow April 14, 2018 FB Mathematik, TU Kaiserslautern, Postfach 3049, 67653 Kaiserslautern, Germany E-mail: [email protected] Abstract For finite groups G with non-abelian, trivial intersection Sylow p-subgroups, the analysis of the Loewy structure of the centre of a block allows us to deduce that a stable equivalence of Morita type does not induce an algebra isomorphism between the centre of the principal block of G and the centre of the Brauer correspondent. This was already known for the Suzuki groups; the result will be generalised to cover more groups with trivial intersection Sylow p-subgroups. Keywords: blocks, trivial intersection defect groups, stable equivalence of Morita type AMS classification: 20C05, 20C15 1 Introduction Let p be a fixed prime number. Let G be a finite group whose order is divisible by p, and P a Sylow p- subgroup of G. Throughout, (K, O, k) is a p-modular system; in particular, k is an algebraically closed field of characteristic p and O is a complete valuation ring whose residue field k has characteristic p. Local representation theory studies the connection between kG and kNG(P ); Brou´e’s abelian de- fect group conjecture (ADGC) predicts the existence of a derived equivalence between the principal blocks B0(kG) and b0(kNG(P )) if the Sylow p-subgroups of G are abelian. We investigate the ques- tion of whether a derived equivalence can exist when the Sylow p-subgroups are non-abelian, trivial intersection subgroups of G.