DOCSLIB.ORG

Book-49708.Pdf

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Book-49708.Pdf Rudolf Ahlswede ¢ Vladimir Blinovsky Lectures on Advances in Combinatorics Rudolf Ahlswede Vladimir Blinovsky Universitat¨ Bielefeld Institute of Information Fakultat¨ f¨urMathematik Transmission Problems Universitatsstr.¨ 25 Russian Academy of Sciences 33615 Bielefeld Bol’shoi karetnyi per. 19 Germany 127994 Moscow [email protected] Russia [email protected] ISBN 978-3-540-78601-6 e-ISBN 978-3-540-78602-3 Library of Congress Control Number: 2008923540 Mathematics Subject Classification (2000): 05-XX, 11-XX, 40-XX, 52-XX, 68-XX, 94-XX °c Springer-Verlag Berlin Heidelberg 2008 This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustra- tions, recitation, broadcasting, reproduction on microfilm or in any other way, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission for use must always be obtained from Springer. Violations are liable to prosecution under the German Copyright Law. The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. Cover design: WMXDesign GmbH, Heidelberg Printed on acid-free paper 9 8 7 6 5 4 3 2 1 springer.com Preface The lectures concentrate on highlights in Combinatorial (Chapters II and III) and Number Theoretical (Chapter IV) Extremal Theory, in particular on the solution of famous problems which were open for many decades. However, the organization of the lectures in six chapters does neither follow the historic developments nor the connections between ideas in several cases. With the specified auxiliary results in Chapter I on Probability Theory, Graph Theory, etc., all chapters can be read and taught independently of one another. In addition to the 16 lectures organized in 6 chapters of the main part of the book, there is supplementary material for most of them in the Appendix. In particu- lar, there are applications and further exercises, research problems, conjectures, and even research programs. The following books and reports [B97], [ACDKPSWZ00], [A01], and [ABCABDM06], mostly of the authors, are frequently cited in this book, especially in the Appendix, and we therefore mark them by short labels as [B], [N], [E], and [G]. We emphasize that there are also “Exercises” in [B], a “Problem Section” with contributions by several authors on pages 1063–1105 of [G], which are often of a combinatorial nature, and “Problems and Conjectures” on pages 172–173 of [E]. The book includes the two well-known results (both in Chapter V), the Ahlswede/Zhang identity, which improves the LYM-inequality, and the Ahlswede/Daykin inequality, which is more general and also sharper than known correlation inequalities in Statistical Physics, Probability Theory, and Combi- natorics (cf. the survey by Fishburn/Shepp in [N], 501–516). These inequali- ties were started in Probability Theory (percolation) around 1960 with Harris, in Combinatorics in 1966 with Kleitman’s Lemma, and in physics 1971 with Fortuin/Kasteleyn/Ginibre (FKG). In many books the AD-inequality (also called “4-Function Theorem”) is viewed in connection with lattices. We emphasize that a much more general inequality of [AD79b] makes no reference to lattices. Its essence is a Cartesian product property of sets and therefore there is a wider range of possible applications. Also there is nothing holy about the number of operations and factors on either side of the inequality as long as proper weight- expansiveness is ensured. In the following, we come to another surprise concerning number-theoretical inequalities. v vi Preface A spectacular series of results started with a lecture in 1992 of Erdos,¨ who raised in 1962 (and repeatedly spoke about) the problem “What is the maximal cardinality of a set of numbers smaller than n with no k + 1 of its members being pairwise relatively prime?” This stimulated Ahlswede and Khachatrian to make a systematic investiga- tion of this and related number-theoretical extremal problems. Its immediate suc- cesses are solutions for several well-known conjectures of Erdos¨ and Erdos/Graham¨ (Chapter VI). More importantly, they gained an understanding for the role of the prime number distribution for such problems, which distinguishes them from com- binatorial extremal problems. These investigations had another surprising fruit. The AD-inequality implies a number-theoretical correlation inequality for Dirichlet den- sities of sets of numbers, which implies and is sharper than the classical inequalities in [H37] and [R37], which settled a conjecture of Hasse concerning an identity due to Dirichlet and Behrend, the number theoretical form of FKG! Number The- ory came first and AD is a crossroad between Pure and Applied Mathematics (in Chapter V). Also another inequality, seemingly without predecessors, was discov- ered. Finally, the analysis led to the discovery of a new “pushing” method with a wide applicability. In particular, it led to the solution of well-known combinator- ial problems like the famous 4m-conjecture (Erdos/Ko/Rado¨ 1938, one of the oldest problems in Combinatorial Extremal Theory) or the diametric problem in Hamming spaces (optimal anticodes). Actually, the 4m-conjecture just concerned the first unsolved case of the follow- A⊂ [n] ing much more general problem: A system of sets k is called t-intersecting if |A1 ∩ A2|≥t for all A1,A2 ∈A, and I(n,k,t) denotes the set of all such systems. Determine the function M(n,k,t)= max |A| and the structure of maximal sys- A∈I(n,k,t) tems! Ahlswede and Khachatrian gave the complete solution for every n,k,t.Ithas a very clear geometrical interpretation (Chapter II). Most lectures in Chapter III are devoted to combinatorics of multiple packings, which are equivalent to list codes in Information Theory and as such relevant for estimating error probabilities. Fundamental works of Blinovsky [B01a] represented here deliver the solutions of the problems for list codes, which were stated by the classics of information theory in the middle of the last century. These problems give a beautiful example of interplay between Extremal Combinatorics and Information Theory. Covering and packing are classical topics in Geometry. In Chapter III they concern sequence spaces for problems primarily motivated by Information Theory: Data Compression and Shannon’s zero error capacity problem of a noisy channel, which is a packing problem for product hypergraphs. A highlight was Lovasz’´ solu- tion of the pentagon case. In general, the progress is rather slow. Here we deal with a related partition problem. Origins of problems and theories, which developed with them, are only briefly discussed because of limited space. However, we consider it especially important for students to think about Mathematics in connection with other sciences and real world phenomena. In fact, a large part of Chapters IV and V originated that way. Stimuli came mostly from questions in Information Theory. We give a quote from [N], page xvi. Preface vii “The deep interplay between several disciplines and a broad philosophical view is a thread through Ahlswede’s work. For him, Information Theory deals with gain- ing information (that is, statistics), transfer of information without and with secrecy constraints (that is, cryptology), and storing information (Memories, Data Compres- sion). Applying ideas from one area to another often led to unexpected and beautiful results and even to new theories. Let us give an example involving storage. Motivated by the practical problem of storing data using a new laser technique, code models for reusable memories were introduced in Information Theory. It turned out that the analysis was much more efficient when stating the question as a combinatorial extremal problem, which led immediately to the connections with hypergraph coloring, novel iso-diametric problems in sequence spaces and finally to the new class of the so-called “Higher- level extremal problems” in Combinatorics. Among them are also Sperner-type questions for “clouds” of antichains. These problems are by one degree more complex than those usually considered: sets take the role of elements, families of sets (clouds) take the role of sets, etc. ([N], P.L. Erdos,¨ L.A. Szekely, 117–124). In another direction, generalizing models for reusable memories, Ahlswede and Zhang introduced write–efficient rewritable memories leading to diametrical prob- lems for sequence spaces. Imagine a tape with n cells into which we can write letters from an alphabet X . n Awordx =(x1,...,xn) stores some messages. When we want to update this record n to a message represented by y =(y1,...,yn) the per letter costs ϕ(xt ,yt ) add up to ϕ n n n ϕ n(x ,y )=∑t=1 (xt ,yt ). When there is a cost constraint D, then we require n n ϕn(x ,y ) ≤ D. To be able to update many messages we come to the diametric problem to charac- terize n n n n M(ϕn,D)=max{|C| : ϕn(x ,y ) ≤ D for all x ,y ∈ C} for the “sum-type” cost ϕn, which can also be a distance function like the Hamming, Taxi or Lee metric, etc. These problems are discussed also in Chapter II (and in the Appendix). There, in Lecture 6, also two families of sequences with constant mutual dis- tances are considered. This falls into the subject of monochromatic rectangles, which arose in Yao’s investigation of communication complexity. The topic of the last lecture in Chapter II also has its origin in Computer Science and was communicated to us by Mullin in 1990. Finally, we emphasize that another approach, the study of extremal problems under dimension constraints (in Chapter IV) has found an application in Computer Science.
Load more

Recommended publications
  • BLECHER • All Numbers Below Are Integers, Usually Positive. • Read Up
    MATH 4389{ALGEBRA `CHEATSHEET'{BLECHER • All numbers below are integers, usually positive. • Read up on e.g. wikipedia on the Euclidean algorithm. • Diophantine equation ax + by = c has solutions iff gcd(a; b) doesn't divide c. One may find the solutions using the Euclidean algorithm (google this). • Euclid's lemma: prime pjab implies pja or pjb. • gcd(m; n) · lcm(m; n) = mn. • a ≡ b (mod m) means mj(a − b). An equivalence relation (reflexive, symmetric, transitive) on the integers. • ax ≡ b (mod m) has a solution iff gcd(m; a)jb. • Division Algorithm: there exist unique integers q and r with a = bq + r and 0 ≤ r < b; so a ≡ r (mod b). • Fermat's theorem: If p is prime then ap ≡ a (mod p) Also, ap−1 ≡ 1 (mod p) if p does not divide a. • For definitions for groups, rings, fields, subgroups, order of element, etc see Algebra fact sheet" below. • Zm = f0; 1; ··· ; m−1g with addition and multiplication mod m, is a group and commutative ring (= Z =m Z) • Order of n in Zm (i.e. smallest k s.t. kn ≡ 0 (mod m)) is m=gcd(m; n). • hai denotes the subgroup generated by a (the smallest subgroup containing a). For example h2i = f0; 2; 2+2 = 4; 2 + 2 + 2 = 6g in Z8. (In ring theory it may be the subring generated by a). • A cyclic group is a group that can be generated by a single element (the group generator). They are abelian. • A finite group is cyclic iff G = fg; g + g; ··· ; g + g + ··· + g = 0g; so G = hgi.
    [Show full text]
  • Countable Torsion-Free Abelian Groups
    COUNTABLE TORSION-FREE ABELIAN GROUPS By M. O'N. CAMPBELL [Received 27 January 1959.—Read 19 February 1959] Introduction IN this paper we present a new classification of the countable torsion-free abelian groups. Since any abelian group 0 may be regarded as an extension of a periodic group (namely the torsion part of G) by a torsion-free group, and since there exists the well-known complete classification of the count- able periodic abelian groups due to Ulm, it is clear that the classification problem studied here is of great interest. By a group we shall always mean an abelian group, and the additive notation will be employed throughout. It is well known that all the maximal linearly independent sets of elements of a given group are car- dinally equivalent; the corresponding cardinal number is the rank of the group. Derry (2) and Mal'cev (4) have studied the torsion-free groups of finite rank only, and have given classifications of these groups in terms of certain equivalence classes of systems of matrices with £>-adic elements. Szekeres (5) attempted to abolish the finiteness restriction on rank; he extracted certain invariants, but did not derive a complete classification. By a basis of a torsion-free group 0 we mean any maximal linearly independent subset of G. A subgroup generated by a basis of G will be called a basal subgroup or described as basal in G. Thus U is a basal sub- group of G if and only if (i) U is free abelian, and (ii) the factor group G/U is periodic.
    [Show full text]
  • Arxiv:1909.05807V1 [Math.RA] 12 Sep 2019 Cs T
    MODULES OVER TRUSSES VS MODULES OVER RINGS: DIRECT SUMS AND FREE MODULES TOMASZ BRZEZINSKI´ AND BERNARD RYBOLOWICZ Abstract. Categorical constructions on heaps and modules over trusses are con- sidered and contrasted with the corresponding constructions on groups and rings. These include explicit description of free heaps and free Abelian heaps, coprod- ucts or direct sums of Abelian heaps and modules over trusses, and description and analysis of free modules over trusses. It is shown that the direct sum of two non-empty Abelian heaps is always infinite and isomorphic to the heap associated to the direct sums of the group retracts of both heaps and Z. Direct sum is used to extend a given truss to a ring-type truss or a unital truss (or both). Free mod- ules are constructed as direct sums of a truss. It is shown that only free rank-one modules are free as modules over the associated truss. On the other hand, if a (finitely generated) module over a truss associated to a ring is free, then so is the corresponding quotient-by-absorbers module over this ring. 1. Introduction Trusses and skew trusses were defined in [3] in order to capture the nature of the distinctive distributive law that characterises braces and skew braces [12], [6], [9]. A (one-sided) truss is a set with a ternary operation which makes it into a heap or herd (see [10], [11], [1] or [13]) together with an associative binary operation that distributes (on one side or both) over the heap ternary operation. If the specific bi- nary operation admits it, a choice of a particular element could fix a group structure on a heap in a way that turns the truss into a ring or a brace-like system (which becomes a brace provided the binary operation admits inverses).
    [Show full text]
  • Groups with Preassigned Central and Central Quotient Group*
    GROUPS WITH PREASSIGNED CENTRAL AND CENTRAL QUOTIENT GROUP* BY REINHOLD BAER Every group G determines two important structural invariants, namely its central C(G) and its central quotient group Q(G) =G/C(G). Concerning these two invariants the following two problems seem to be most elementary. If A and P are two groups, to find necessary and sufficient conditions for the existence of a group G such that A and C(G), B and Q(G) are isomorphic (existence problem) and to find necessary and sufficient conditions for the existence of an isomorphism between any two groups G' and G" such that the groups A, C(G') and C(G") as well as the groups P, Q(G') and Q(G") are isomorphic (uniqueness problem). This paper presents a solution of the exist- ence problem under the hypothesis that P (the presumptive central quotient group) is a direct product of (a finite or infinite number of finite or infinite) cyclic groups whereas a solution of the uniqueness problem is given only un- der the hypothesis that P is an abelian group with a finite number of genera- tors. There is hardly any previous work concerning these problems. Only those abelian groups with a finite number of generators which are central quotient groups of suitable groups have been characterized before, t 1. Before enunciating our principal results (in §2) some notation and con- cepts concerning abelian groups will have to be recorded for future reference. If G is any abelian group, then the composition of the elements in G is denoted as addition: x+y.
    [Show full text]
  • Group Theory
    Algebra Math Notes • Study Guide Group Theory Table of Contents Groups..................................................................................................................................................................... 3 Binary Operations ............................................................................................................................................................. 3 Groups .............................................................................................................................................................................. 3 Examples of Groups ......................................................................................................................................................... 4 Cyclic Groups ................................................................................................................................................................... 5 Homomorphisms and Normal Subgroups ......................................................................................................................... 5 Cosets and Quotient Groups ............................................................................................................................................ 6 Isomorphism Theorems .................................................................................................................................................... 7 Product Groups ...............................................................................................................................................................
    [Show full text]
  • Countable Torsion Products of Abelian /^-Groups E
    proceedings of the american mathematical society Volume 37, Number 1, January 1973 COUNTABLE TORSION PRODUCTS OF ABELIAN /^-GROUPS E. L. LADY Abstract. Let Au A2, • ■■ be direct sums of cyclic/j-groups, and G=r]^7" An be the torsion subgroup of the product. The product decomposition is used to define a topology on G in which each G [pT]is complete and the restriction to G[pr] of any endomorphism is continuous. Theorems are then derived dual to those proved by Irwin, Richman and Walker for countable direct sums of torsion complete groups. It is shown that every subgroup of G[p] supports a pure subgroup of G, and that if G=H®K, then H^tTTy Gn, where the G„ are direct sums of cyclics. A weak isomorphic refine- ment theorem is proved for decompositions of G as a torsion product. Finally, in answer to a question of Irwin and O'Neill, an example is given of a direct decomposition of G that is not induced by a decomposition of Y~[y A„. 1. The product topology. Let G=tT~[x An be the torsion subgroup of \~[y An, where the An are abelian /»-groups. For each nonnegative integer n, let Gn=t \~jr> n A{, considered as a subgroup of G in the natural way. The product topology on G is defined by taking the Gn to be a neigh- borhood basis at 0. Thus the product topology is the topology that t \~\x An inherits as a subspace of the cartesian product of the An, where these are considered discrete.
    [Show full text]
  • Admissible Direct Decompositions of Direct Sums of Abelian Groups of Rank One
    Separatunt PUBLICATION ES MATHEHATICAE TOMUS 10. FASC. DEBRECEN 1963 FUNDAVERUNT: A. O M T. SZELE ET O. VARGA COMMI SSI O REDACTORUM: J. ACZÉL, B. GY1RES, A. KERTÉSZ, A. RAPCSAK, A. RÉNYI, ET O. VARGA SECRETARIUS COMMI SSI ON'S: B. BARNA L. G. Kovics Admissible direct decompositions of direct sums o f abelian groups o f rank one INSTITUTUM M AT H EM AT IC U M U N IVER SITATIS DEBRECENIENSIS HUNGARIA 254 Admissible direct decompositions of direct sums of abelian groups of rank one By L. G. KOVAC S (Manchester) The starting point o f the theory o f ordinary representations is MASCHKE'S Theorem, which states that every representation of a finite group over a field whose characteristic does not divide the order o f the group is completely reducible (see e. g. VAN DER WAERDEN [6], p. 182). A partial generalization of this theorem has recently been given by O. GRÜN in [2], and the main step of the classical proof of the theorem has been generalized by M. F. NEWMAN and the author in [4]. Both of these results arose out of a shift in the point of view: they do not refer to repre- sentations, but to direct decompositions of abelian groups, admissible with respect to a finite group of operators (in the sense of KUROSH [5], § 15). The aim o f this paper is to present an extension of GRON's result, exploiting the start made in [4]. The terminology follows, apart from minor deviations, that o f FUCHS'S book [1].
    [Show full text]
  • Have Talked About Since the First Exam Normal Subgroups. the Integers
    Math 417 Group Theory Second Exam Things we (will) have talked about since the first exam Normal subgroups. The integers mod n can be viewed either as having elements {0, 1,...,n− 1}, or the elements are equivalence classes of integers, where a ∼ b if n|b − a. In the latter case, we add elements by adding representatives of equivalence classes (and then need to show that the resulting ‘element’ is independent of the choices made). This notion can be generalized: For G a group and H ≤ G a subgroup, defining a multiplication on (left) cosets by (aH)(bH)= (ab)H requires, to be well-defined, that a1H = a2H and b1H = b2H implies (a1b1)H = −1 −1 −1 −1 −1 2 −1 (a2b2)H. That is, we need a1 a2, b1 b2 ∈ H implies (a1b1) (a2b2) = b1 (a1 a )b1(b1 b2) is −1 −1 2 −1 in H. This then requires b1 (a1 a )b1 = b1 hb1 ∈ H for every b1 ∈ G and h ∈ H. So we define: H ≤ G is a normal subgroup of G if g−1Hg = {g−1hg : h ∈ H} = H for every g ∈ G. Then the multiplication above makes the set of (left) cosets G/H = {gH : g ∈ G} a group. −1 −1 H = eGH is the identity element, and (gH) = g H. The order of G/H is the number of cosets of H in G, i.e., the index [G : H] of H in G. We use H⊳G to denote “H is normal in G”. We call G/H the quotient of G by H.
    [Show full text]
  • Primary Decomposition Theorem for Finite Abelian Groups
    Subject : MATHEMATICS Paper 1 : ABSTRACT ALGEBRA Chapter 1 : Direct Product of Groups Module 3 : Primary decomposition theorem for finite abelian groups Anjan Kumar Bhuniya Department of Mathematics Visva-Bharati; Santiniketan West Bengal 1 Primary decomposition theorem for finite abelian groups Learning outcomes: 1. p-primary abelian groups. 2. Primary Decomposition Theorem. 3. p-primary components. In this module we prove that every finite abelian group can be expressed as an internal direct product of a family of p-primary subgroups. In most of the results on the structure of finite abelian groups the feature that plays the most powerful role is that every finite abelian group is a Z-module. So, it is convenient to consider addition as the binary operation in the study of finite abelian groups. Internal direct product of a family of subgroups G1;G2; ··· ;Gk of a group G, if it is abelian, is called direct sum of G1;G2; ··· ;Gk and is denoted by G1 ⊕ G2 ⊕ · · · ⊕ Gk. Thus a finite abelian group G is a direct sum of subgroups G1;G2; ··· ;Gk if and only if G = G1 + G2 + ··· + Gk and Gi \(G1 +···+Gi−1 +Gi+1 +···+Gk) = f0g for every i = 1; 2; ··· ; k. In view of the fact that every internal direct sum of the subgroups G1;G2; ··· ;Gk is isomorphic to the external direct product of G1;G2; ··· ;Gk, we call both the internal direct sum and the external direct product simply as direct sum and use the notation G1 ⊕G2 ⊕· · ·⊕Gk to represent direct sum of groups G1;G2; ··· ;Gk. Definition 0.1.
    [Show full text]
  • The Characterization of a Line Arrangement Whose Fundamental Group of the Complement Is a Direct Sum of Free Groups
    Algebraic & Geometric Topology 10 (2010) 1285–1304 1285 The characterization of a line arrangement whose fundamental group of the complement is a direct sum of free groups MEITAL ELIYAHU ERAN LIBERMAN MALKA SCHAPS MINA TEICHER Kwai Man Fan proved that if the intersection lattice of a line arrangement does not contain a cycle, then the fundamental group of its complement is a direct sum of infinite and cyclic free groups. He also conjectured that the converse is true as well. The main purpose of this paper is to prove this conjecture. 14F35, 32S22; 14N30, 52C30 1 Introduction An arrangement of lines is a finite collection of C–affine subspaces of dimension 1. For such an arrangement † C2 , there is a natural projective arrangement † of  lines in CP 2 associated to it, obtained by adding to each line its corresponding point at infinity. The problem of finding connections between the topology of C2 † and the combinatorial theory of † is one of the main problems in the theory of line arrangements (see for example Cohen and Suciu [3]). The main motivations for studying the topology of C2 † are derived from the areas of hypergeometric functions, singularity theory and algebraic geometry. Given an arrangement †, we define the graph G.†/ in the way it is defined by Fan [7]. We first connect all higher multiple points of † which lie on a line Li by an arbitrary simple arc ˛i Li which does not go through any double point of †. Taking the union of the set of all higher multiple points and all of this simple arcs, we obtain G.†/.
    [Show full text]
  • Self-Small Abelian Groups
    Bull. Aust. Math. Soc. 80 (2009), 205–216 doi:10.1017/S0004972709000185 SELF-SMALL ABELIAN GROUPS ULRICH ALBRECHT ˛, SIMION BREAZ and WILLIAM WICKLESS (Received 23 October 2008) Abstract This paper investigates self-small abelian groups of finite torsion-free rank. We obtain a new characterization of infinite self-small groups. In addition, self-small groups of torsion-free rank 1 and their finite direct sums are discussed. 2000 Mathematics subject classification: primary 20K21. Keywords and phrases: self-small group, projection condition, essentially W-reduced group. 1. Introduction It is the goal of this paper to investigate self-small abelian groups. Introduced by Arnold and Murley [6], these are the abelian groups G such that, for every index .I / L set I and every α 2 Hom.G; G /, there is a finite subset J ⊆ I with α.G/ ⊆ J G. Since every torsion-free abelian group of finite rank is self-small, and all self-small torsion groups are finite by [6, Proposition 3.1], our investigation focuses on mixed groups. Section 2 introduces several important classes of self-small mixed groups, and discusses their basic properties. In Section 3 we give a new characterization of infinite self-small groups of finite torsion-free rank (Theorem 3.1), while Section 4 extends the notion of completely decomposable groups from the torsion-free case to the case of mixed groups. Although we use the standard notation from [12], some terminology shall be mentioned for the benefit of the reader. A mixed abelian group G is honest if tG L is not a direct summand of G, where tG D p G p denotes the torsion subgroup of G, and G p is its p-torsion subgroup.
    [Show full text]
  • Abstract Algebra
    Abstract Algebra Groups, Rings and Fields, Advanced Group Theory, Modules and Noetherian Rings, Field Theory YOTSANAN MEEMARK Semi-formal based on the graduate courses 2301613–4 Abstract Algebra I & II, offered at Department of Mathematics and Computer Science, Faculty of Science, Chulalongkorn University Published by Yotsanan Meemark Department of Mathematics and Computer Science Faculty of Science, Chulalongkorn University, Bangkok, 10330 Thailand First digital edition October 2013 First bound edition May 2014 Second bound edition August 2015 Available for free download at http://pioneer.netserv.chula.ac.th/~myotsana/ Please cite this book as: Y. Meemark, Abstract Algebra, 2015, PDF available at http://pioneer.netserv.chula.ac.th/~myotsana/ Any comment or suggestion, please write to [email protected] c 2015 by Yotsanan Meemark. Meemark, Yotsanan Abstract Algebra / Yotsanan Meemark – 2nd ed. Bangkok: Danex Intercorporation Co., Ltd., 2015. 195pp. ISBN 978-616-361-389-9 Printed by Danex Intercorporation Co., Ltd., Bangkok, Thailand. www.protexts.com Foreword This book is written based on two graduate abstract algebra courses offered at Department of Mathematics and Computer Science, Faculty of Science, Chulalongkorn University. It grows out of my lecture notes that I used while I was teaching those courses many times. My intention is to develop essential topics in algebra that can be used in research as illustrated some in the final chapter. Also, it can be served as a standard reference for preparing for a qualifying examination in Algebra. I have tried to make it self-contained as much as possible. However, it may not be suitable for reading it for the first course in abstract algebra.
    [Show full text]