A Study on Algebra of Groups and Rings Structures in Mathematics
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Geometric Algebra for Vector Fields Analysis and Visualization: Mathematical Settings, Overview and Applications Chantal Oberson Ausoni, Pascal Frey
Geometric algebra for vector fields analysis and visualization: mathematical settings, overview and applications Chantal Oberson Ausoni, Pascal Frey To cite this version: Chantal Oberson Ausoni, Pascal Frey. Geometric algebra for vector fields analysis and visualization: mathematical settings, overview and applications. 2014. hal-00920544v2 HAL Id: hal-00920544 https://hal.sorbonne-universite.fr/hal-00920544v2 Preprint submitted on 18 Sep 2014 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Geometric algebra for vector field analysis and visualization: mathematical settings, overview and applications Chantal Oberson Ausoni and Pascal Frey Abstract The formal language of Clifford’s algebras is attracting an increasingly large community of mathematicians, physicists and software developers seduced by the conciseness and the efficiency of this compelling system of mathematics. This contribution will suggest how these concepts can be used to serve the purpose of scientific visualization and more specifically to reveal the general structure of complex vector fields. We will emphasize the elegance and the ubiquitous nature of the geometric algebra approach, as well as point out the computational issues at stake. 1 Introduction Nowadays, complex numerical simulations (e.g. in climate modelling, weather fore- cast, aeronautics, genomics, etc.) produce very large data sets, often several ter- abytes, that become almost impossible to process in a reasonable amount of time. -
Exploring Physics with Geometric Algebra, Book II., , C December 2016 COPYRIGHT
peeter joot [email protected] EXPLORINGPHYSICSWITHGEOMETRICALGEBRA,BOOKII. EXPLORINGPHYSICSWITHGEOMETRICALGEBRA,BOOKII. peeter joot [email protected] December 2016 – version v.1.3 Peeter Joot [email protected]: Exploring physics with Geometric Algebra, Book II., , c December 2016 COPYRIGHT Copyright c 2016 Peeter Joot All Rights Reserved This book may be reproduced and distributed in whole or in part, without fee, subject to the following conditions: • The copyright notice above and this permission notice must be preserved complete on all complete or partial copies. • Any translation or derived work must be approved by the author in writing before distri- bution. • If you distribute this work in part, instructions for obtaining the complete version of this document must be included, and a means for obtaining a complete version provided. • Small portions may be reproduced as illustrations for reviews or quotes in other works without this permission notice if proper citation is given. Exceptions to these rules may be granted for academic purposes: Write to the author and ask. Disclaimer: I confess to violating somebody’s copyright when I copied this copyright state- ment. v DOCUMENTVERSION Version 0.6465 Sources for this notes compilation can be found in the github repository https://github.com/peeterjoot/physicsplay The last commit (Dec/5/2016), associated with this pdf was 595cc0ba1748328b765c9dea0767b85311a26b3d vii Dedicated to: Aurora and Lance, my awesome kids, and Sofia, who not only tolerates and encourages my studies, but is also awesome enough to think that math is sexy. PREFACE This is an exploratory collection of notes containing worked examples of more advanced appli- cations of Geometric Algebra (GA), also known as Clifford Algebra. -
The Universal Property of Inverse Semigroup Equivariant KK-Theory
KYUNGPOOK Math. J. 61(2021), 111-137 https://doi.org/10.5666/KMJ.2021.61.1.111 pISSN 1225-6951 eISSN 0454-8124 c Kyungpook Mathematical Journal The Universal Property of Inverse Semigroup Equivariant KK-theory Bernhard Burgstaller Departamento de Matematica, Universidade Federal de Santa Catarina, CEP 88.040-900 Florian´opolis-SC, Brasil e-mail : [email protected] Abstract. Higson proved that every homotopy invariant, stable and split exact func- tor from the category of C∗-algebras to an additive category factors through Kasparov's KK-theory. By adapting a group equivariant generalization of this result by Thomsen, we generalize Higson's result to the inverse semigroup and locally compact, not necessarily Hausdorff groupoid equivariant setting. 1. Introduction In [3], Cuntz noted that if F is a homotopy invariant, stable and split exact func- tor from the category of separable C∗-algebras to the category of abelian groups then Kasparov's KK-theory acts on F , that is, every element of KK(A; B) induces a natural map F (A) ! F (B). Higson [4], on the other hand, developed Cuntz' find- ings further and proved that every such functor F factorizes through the category K consisting of separable C∗-algebras as the object class and KK-theory together with the Kasparov product as the morphism class, that is, F is the composition F^ ◦ κ of a universal functor κ from the class of C∗-algebras to K and a functor F^ from K to abelian groups. In [12], Thomsen generalized Higson's findings to the group equivariant setting by replacing everywhere in the above statement algebras by equivariant algebras, ∗- homomorphisms by equivariant ∗-homomorphisms and KK-theory by equivariant KK-theory (the proof is however far from such a straightforward replacement). -
An Introduction to Inverse Semigroups and Their Connections to C*-Algebras
CARLETON UNIVERSITY SCHOOL OF MATHEMATICS AND STATISTICS HONOURS PROJECT TITLE: An Introduction to Inverse Semigroups and Their Connections To C*-Algebras AUTHOR: Kyle Cheaney SUPERVISOR: Dr. Charles Starling DATE: August 24, 2020 AN INTRODUCTION TO INVERSE SEMIGROUPS AND THEIR CONNECTIONS TO C∗-ALGEBRAS KYLE CHEANEY: 101012022 Abstract. This paper sets out to provide the reader with a basic introduction to inverse semigroups, as well as a proof of the Wagner-Preston Representation Theorem. It then focuses on finite directed graphs, specifically the graph inverse semigroup and how properties of the semigroup correspond to properties of C∗ algebras associated to such graphs. 1. Introduction The study of inverse semigroups was founded in the 1950's by three mathematicians: Ehresmann, Preston, and Wagner, as a way to algebraically describe pseudogroups of trans- formations. The purpose of this paper is to introduce the topic of inverse semigroups and some of the basic properties and theorems. We use these basics to relate the inverse semi- group formed by a directed graph to the corresponding graph C∗ algebra. The study of such C∗ algebras is still an active topic of research in analysis, thus providing a connection between abstract algebraic objects and complex analysis. In section 2, we outline some preliminary definitions and results which will be our basic tools for working with inverse semigroups. Section 3 provides a more detailed introduction to inverse semigroups and contains a proof of the Wagner-Preston representation theorem, a cornerstone in the study of inverse semigroups. In section 4, we present some detailed examples of inverse semigroups, including proving said sets are in fact inverse semigroups and discussing what their idempotents look like. -
On the Semisimplicity of Group Algebras
ON THE SEMISIMPLICITY OF GROUP ALGEBRAS ORLANDO E. VILLAMAYOR1 In this paper we find sufficient conditions for a group algebra over a commutative ring to be semisimple. In particular, the case in which the group is abelian is solved for fields of characteristic zero, and, in a more general case, for semisimple commutative rings which are uniquely divisible by every integer. Under similar restrictions on the ring of coefficients, it is proved the semisimplicity of group alge- bras when the group is not abelian but the factor group module its center is locally finite.2 In connection with this problem, we study homological properties of group algebras generalizing some results of M. Auslander [l, Theorems 6 and 9]. In fact, Lemmas 3 and 4 give new proofs of Aus- lander's Theorems 6 and 9 in the case C=(l). 1. Notations. A group G will be called a torsion group if every ele- ment of G has finite order, it will be called locally finite if every finitely generated subgroup is finite and it will be called free (or free abelian) if it is a direct sum of infinite cyclic groups. Direct sum and direct product are defined as in [3]. Given a set of rings Ri, their direct product will be denoted by J{Ri. If G is a group and R is a ring, the group algebra generated by G over R will be denoted by R(G). In a ring R, radical and semisimplicity are meant in the sense of Jacobson [5]. A ring is called regular in the sense of von Neumann [7]. -
EVARISTE GALOIS the Long Road to Galois CHAPTER 1 Babylon
A radical life EVARISTE GALOIS The long road to Galois CHAPTER 1 Babylon How many miles to Babylon? Three score miles and ten. Can I get there by candle-light? Yes, and back again. If your heels are nimble and light, You may get there by candle-light.[ Babylon was the capital of Babylonia, an ancient kingdom occupying the area of modern Iraq. Babylonian algebra B.M. Tablet 13901-front (From: The Babylonian Quadratic Equation, by A.E. Berryman, Math. Gazette, 40 (1956), 185-192) B.M. Tablet 13901-back Time Passes . Centuries and then millennia pass. In those years empires rose and fell. The Greeks invented mathematics as we know it, and in Alexandria produced the first scientific revolution. The Roman empire forgot almost all that the Greeks had done in math and science. Germanic tribes put an end to the Roman empire, Arabic tribes invaded Europe, and the Ottoman empire began forming in the east. Time passes . Wars, and wars, and wars. Christians against Arabs. Christians against Turks. Christians against Christians. The Roman empire crumbled, the Holy Roman Germanic empire appeared. Nations as we know them today started to form. And we approach the year 1500, and the Renaissance; but I want to mention two events preceding it. Al-Khwarismi (~790-850) Abu Ja'far Muhammad ibn Musa Al-Khwarizmi was born during the reign of the most famous of all Caliphs of the Arabic empire with capital in Baghdad: Harun al Rashid; the one mentioned in the 1001 Nights. He wrote a book that was to become very influential Hisab al-jabr w'al-muqabala in which he studies quadratic (and linear) equations. -
SOME ALGEBRAIC DEFINITIONS and CONSTRUCTIONS Definition
SOME ALGEBRAIC DEFINITIONS AND CONSTRUCTIONS Definition 1. A monoid is a set M with an element e and an associative multipli- cation M M M for which e is a two-sided identity element: em = m = me for all m M×. A−→group is a monoid in which each element m has an inverse element m−1, so∈ that mm−1 = e = m−1m. A homomorphism f : M N of monoids is a function f such that f(mn) = −→ f(m)f(n) and f(eM )= eN . A “homomorphism” of any kind of algebraic structure is a function that preserves all of the structure that goes into the definition. When M is commutative, mn = nm for all m,n M, we often write the product as +, the identity element as 0, and the inverse of∈m as m. As a convention, it is convenient to say that a commutative monoid is “Abelian”− when we choose to think of its product as “addition”, but to use the word “commutative” when we choose to think of its product as “multiplication”; in the latter case, we write the identity element as 1. Definition 2. The Grothendieck construction on an Abelian monoid is an Abelian group G(M) together with a homomorphism of Abelian monoids i : M G(M) such that, for any Abelian group A and homomorphism of Abelian monoids−→ f : M A, there exists a unique homomorphism of Abelian groups f˜ : G(M) A −→ −→ such that f˜ i = f. ◦ We construct G(M) explicitly by taking equivalence classes of ordered pairs (m,n) of elements of M, thought of as “m n”, under the equivalence relation generated by (m,n) (m′,n′) if m + n′ = −n + m′. -
Matrix Lie Groups
Maths Seminar 2007 MATRIX LIE GROUPS Claudiu C Remsing Dept of Mathematics (Pure and Applied) Rhodes University Grahamstown 6140 26 September 2007 RhodesUniv CCR 0 Maths Seminar 2007 TALK OUTLINE 1. What is a matrix Lie group ? 2. Matrices revisited. 3. Examples of matrix Lie groups. 4. Matrix Lie algebras. 5. A glimpse at elementary Lie theory. 6. Life beyond elementary Lie theory. RhodesUniv CCR 1 Maths Seminar 2007 1. What is a matrix Lie group ? Matrix Lie groups are groups of invertible • matrices that have desirable geometric features. So matrix Lie groups are simultaneously algebraic and geometric objects. Matrix Lie groups naturally arise in • – geometry (classical, algebraic, differential) – complex analyis – differential equations – Fourier analysis – algebra (group theory, ring theory) – number theory – combinatorics. RhodesUniv CCR 2 Maths Seminar 2007 Matrix Lie groups are encountered in many • applications in – physics (geometric mechanics, quantum con- trol) – engineering (motion control, robotics) – computational chemistry (molecular mo- tion) – computer science (computer animation, computer vision, quantum computation). “It turns out that matrix [Lie] groups • pop up in virtually any investigation of objects with symmetries, such as molecules in chemistry, particles in physics, and projective spaces in geometry”. (K. Tapp, 2005) RhodesUniv CCR 3 Maths Seminar 2007 EXAMPLE 1 : The Euclidean group E (2). • E (2) = F : R2 R2 F is an isometry . → | n o The vector space R2 is equipped with the standard Euclidean structure (the “dot product”) x y = x y + x y (x, y R2), • 1 1 2 2 ∈ hence with the Euclidean distance d (x, y) = (y x) (y x) (x, y R2). -
A Review of Commutative Ring Theory Mathematics Undergraduate Seminar: Toric Varieties
A REVIEW OF COMMUTATIVE RING THEORY MATHEMATICS UNDERGRADUATE SEMINAR: TORIC VARIETIES ADRIANO FERNANDES Contents 1. Basic Definitions and Examples 1 2. Ideals and Quotient Rings 3 3. Properties and Types of Ideals 5 4. C-algebras 7 References 7 1. Basic Definitions and Examples In this first section, I define a ring and give some relevant examples of rings we have encountered before (and might have not thought of as abstract algebraic structures.) I will not cover many of the intermediate structures arising between rings and fields (e.g. integral domains, unique factorization domains, etc.) The interested reader is referred to Dummit and Foote. Definition 1.1 (Rings). The algebraic structure “ring” R is a set with two binary opera- tions + and , respectively named addition and multiplication, satisfying · (R, +) is an abelian group (i.e. a group with commutative addition), • is associative (i.e. a, b, c R, (a b) c = a (b c)) , • and the distributive8 law holds2 (i.e.· a,· b, c ·R, (·a + b) c = a c + b c, a (b + c)= • a b + a c.) 8 2 · · · · · · Moreover, the ring is commutative if multiplication is commutative. The ring has an identity, conventionally denoted 1, if there exists an element 1 R s.t. a R, 1 a = a 1=a. 2 8 2 · ·From now on, all rings considered will be commutative rings (after all, this is a review of commutative ring theory...) Since we will be talking substantially about the complex field C, let us recall the definition of such structure. Definition 1.2 (Fields). -
Algebraic Structures Lecture 18 Thursday, April 4, 2019 1 Type
Harvard School of Engineering and Applied Sciences — CS 152: Programming Languages Algebraic structures Lecture 18 Thursday, April 4, 2019 In abstract algebra, algebraic structures are defined by a set of elements and operations on those ele- ments that satisfy certain laws. Some of these algebraic structures have interesting and useful computa- tional interpretations. In this lecture we will consider several algebraic structures (monoids, functors, and monads), and consider the computational patterns that these algebraic structures capture. We will look at Haskell, a functional programming language named after Haskell Curry, which provides support for defin- ing and using such algebraic structures. Indeed, monads are central to practical programming in Haskell. First, however, we consider type constructors, and see two new type constructors. 1 Type constructors A type constructor allows us to create new types from existing types. We have already seen several different type constructors, including product types, sum types, reference types, and parametric types. The product type constructor × takes existing types τ1 and τ2 and constructs the product type τ1 × τ2 from them. Similarly, the sum type constructor + takes existing types τ1 and τ2 and constructs the product type τ1 + τ2 from them. We will briefly introduce list types and option types as more examples of type constructors. 1.1 Lists A list type τ list is the type of lists with elements of type τ. We write [] for the empty list, and v1 :: v2 for the list that contains value v1 as the first element, and v2 is the rest of the list. We also provide a way to check whether a list is empty (isempty? e) and to get the head and the tail of a list (head e and tail e). -
GEOMETRY and GROUPS These Notes Are to Remind You of The
GEOMETRY AND GROUPS These notes are to remind you of the results from earlier courses that we will need at some point in this course. The exercises are entirely optional, although they will all be useful later in the course. Asterisks indicate that they are harder. 0.1 Metric Spaces (Metric and Topological Spaces) A metric on a set X is a map d : X × X → [0, ∞) that satisfies: (a) d(x, y) > 0 with equality if and only if x = y; (b) Symmetry: d(x, y) = d(y, x) for all x, y ∈ X; (c) Triangle Rule: d(x, y) + d(y, z) > d(x, z) for all x, y, z ∈ X. A set X with a metric d is called a metric space. For example, the Euclidean metric on RN is given by d(x, y) = ||x − y|| where v u N ! u X 2 ||a|| = t |an| n=1 is the norm of a vector a. This metric makes RN into a metric space and any subset of it is also a metric space. A sequence in X is a map N → X; n 7→ xn. We often denote this sequence by (xn). This sequence converges to a limit ` ∈ X when d(xn, `) → 0 as n → ∞ . A subsequence of the sequence (xn) is given by taking only some of the terms in the sequence. So, a subsequence of the sequence (xn) is given by n 7→ xk(n) where k : N → N is a strictly increasing function. A metric space X is (sequentially) compact if every sequence from X has a subsequence that converges to a point of X. -
Forms of the Affine Line and Its Additive Group
Pacific Journal of Mathematics FORMS OF THE AFFINE LINE AND ITS ADDITIVE GROUP PETER RUSSELL Vol. 32, No. 2 February 1970 PACIFIC JOURNAL OF MATHEMATICS Vol. 32, No. 2, 1970 FORMS OF THE AFFINE LINE AND ITS ADDITIVE GROUP PETER RUSSELL Let k be a field, Xo an object (e.g., scheme, group scheme) defined over k. An object X of the same type and isomorphic to Xo over some field K z> k is called a form of Xo. If k is 1 not perfect, both the affine line A and its additive group Gtt have nontrivial sets of forms, and these are investigated here. Equivalently, one is interested in ^-algebras R such that K ®k R = K[t] (the polynomial ring in one variable) for some field K => ky where, in the case of forms of Gα, R has a group (or co-algebra) structure s\R—>R®kR such that (K®s)(t) = £ ® 1 + 1 ® ί. A complete classification of forms of Gα and their principal homogeneous spaces is given and the behaviour of the set of forms under base field extension is studied. 1 If k is perfect, all forms of A and Gα are trivial, as is well known (cf. 1.1). So assume k is not perfect of characteristic p > 0. Then a nontrivial example (cf. [5], p. 46) of a form of Gα is the subgroup of Gα = Spec k[x, y] defined by yp = x + axp where aek, agkp. We show that this example is quite typical (cf. 2.1): Every form of Gtt pn is isomorphic to a subgroup of G« defined by an equation y = aQx + p pm atx + + amx , cii ek, aQΦ 0.