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• The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

#### On one-dimensional dynamical systems and commuting elements in non-commutative algebras

Tumwesigye, Alex Behakanira January 2016 (has links)
This thesis work is about commutativity which is a very important topic in mathematics, physics, engineering and many other fields. Two processes are said to be commutative if the order of "operation" of these processes does not matter. A typical example of two processes in real life that are not commutative is the process of opening the door and the process of going through the door. In mathematics, it is well known that matrix multiplication is not always commutative. Commutating operators play an essential role in mathematics, physics engineering and many other fields. A typical example of the importance of commutativity comes from signal processing. Signals pass through filters (often called operators on a Hilbert space by mathematicians) and commutativity of two operators corresponds to having the same result even when filters are interchanged. Many important relations in mathematics, physics and engineering are represented by operators satisfying a number of commutation relations. In chapter two of this thesis we treat commutativity of monomials of operatos satisfying certain commutation relations in relation to one-dimensional dynamical systems. We derive explicit conditions for commutativity of the said monomials in relation to the existence of periodic points of certain one-dimensional dynamical systems. In chapter three, we treat the crossed product algebra for the algebra of piecewise constant functions on given set, describe the commutant of this algebra of functions which happens to be the maximal commutative subalgebra of the crossed product containing this algebra. In chapter four, we give a characterization of the commutant for the algebra of piecewise constant functions on the real line, by comparing commutants for a non decreasing sequence of algebras.
2

#### Two Characterizations of Commutativity for C*-algebra

Ko, Chun-Chieh 11 June 2002 (has links)
In this thesis, We investigate the problem of when a C*-algebra is commutative through continuous functional calculus, The principal results are that: (1) A C*-algebra A is commutative if and only if e^(ix)e^(iy)=e^(iy)e^(ix), for all self-adjoint elements x,y in A. (2) A C*-algebra A is commutative if and only if e^(x)e^(y)=e^(y)e^(x) for all positive elements x,y in A. We will give an extension of (2) as follows: Let f:[a,b]-->[c,d] be any continuous strictly monotonic function where a,b,c,d in R, a<b,c<d. Then a C*-algebra A is commutative if and only if f(x)f(y)=f(y)f(x), for all self-adjoint elements x,y in A with spec(x) in [a,b] and spec(y) in [a,b].
3

#### Centra of Quiver Algebras

Gawell, Elin January 2014 (has links)
A partly (anti-)commutative quiver algebra is a quiver algebra bound by an (anti-)commutativity ideal, that is, a quadratic ideal generated by monomials and (anti-)commutativity relations. We give a combinatorial description of the ideals and the associated generator graphs, from which one can quickly determine if the ideal is admissible or not. We describe the center of a partly (anti-)commutative quiveralgebra and state necessary and sufficient conditions for the center to be finitely genteratedas a K-algebra.Examples are provided of partly (anti-)commutative quiver algebras that are Koszul algebras. Necessary and sufficient conditions for finite generation of the Hochschild cohomology ring modulo nilpotent elements for a partly (anti-)commutative Koszul quiver algebra are given.
4

#### Deformações e invariâncias em modelos supersimétricos em três e quatro dimensões espaçotemporais

Ipia, Carlos Andrés Palechor January 2017 (has links)
5

#### Hur elever resonerar om kommutativitet i numeriska uttryck / How students reason about commutativity in numerical expressions

Holm, Karolina January 2018 (has links)
Ett av grundskolans uppdrag är att elever ska utveckla kunskap om de fyra räknesättens olika egenskaper. En sådan egenskap är kommutativitet för räknesättet addition, vilket innebär att termers rumsliga placering inte har betydelse för summan. Inom kunskapsområdet aritmetik och algebra är kunskap om den kommutativa egenskapen av vikt. I denna studie intervjuades tio elever i årskurs 2. Intervjuerna var semistrukturerade, vilket bland annat innebar att en intervjuguide följdes. Syftet var att kvalitativt beskriva hur elever resonerar kring operationer med tydlig kommutativitet genom att också använda operationer utan kommutativa egenskaper. Analysen visar att eleverna kan fokusera på olika aspekter av kommutativitet, de kan fokusera på summan, på termerna eller på operationen. Studien visar också att det förekommer elever som övergeneraliserar den kommutativa egenskapen till att gälla vid uttryck med subtraktion. / According to the curriculum, students in elementary school should develop their understanding of the different properties of addition, subtraction, multiplication and division. One property is commutativity for addition. Which means that the terms’ spatial position does not change the sum. A solid understanding of the commutative property is of importance in arithmetic but also in algebra. This qualitative study is based on interviews with ten students in second grade. The purpose of the study is to investigate how students reason when they meet sequences with commutative and non-commutative expressions. The result is that students tend to describe commutativity by focusing on either the sum, the terms or the operation. Students in the study also overgeneralize the commutative property to expression with subtraction.
6

#### A probabilistic approach to a classical result of ore

Muhie, Seid Kassaw 31 August 2021 (has links)
The subgroup commutativity degree sd(G) of a finite group G was introduced almost ten years ago and deals with the number of commuting subgroups in the subgroups lattice L(G) of G. The extremal case sd(G) = 1 detects a class of groups classified by Iwasawa in 1941 (in fact sd(G) represents a probabilistic measure which allows us to understand how far is G from the groups of Iwasawa). Among them we have sd(G) = 1 when L(G) is distributive, that is, when G is cyclic. The characterization of a cyclic group by the distributivity of its lattice of subgroups is due to a classical result of Ore in 1938. Therefore sd(G) is strongly related to structural properties of L(G). Here we introduce a new notion of probability gsd(G) in which two arbitrary sublattices S(G) and T(G) of L(G) are involved simultaneously. In case S(G) = T(G) = L(G), we find exactly sd(G). Upper and lower bounds in terms of gsd(G) and sd(G) are among our main contributions, when the condition S(G) = T(G) = L(G) is removed. Then we investigate the problem of counting the pairs of commuting subgroups via an appropriate graph. Looking at the literature, we noted that a similar problem motivated the permutability graph of non–normal subgroups ΓN (G) in 1995, that is, the graph where all proper non– normal subgroups of G form the vertex set of ΓN (G) and two vertices H and K are joined if HK = KH. The graph ΓN (G) has been recently generalized via the notion of permutability graph of subgroups Γ(G), extending the vertex set to all proper subgroups of G and keeping the same criterion to join two vertices. We use gsd(G), in order to introduce the non–permutability graph of subgroups ΓL(G) ; its vertices are now given by the set L(G) − CL(G)(L(G)), where CL(G)(L(G)) is the smallest sublattice of L(G) containing all permutable subgroups of G, and we join two vertices H, K of ΓL(G) if HK 6= KH. We finally study some classical invariants for ΓL(G) and find numerical relations between the number of edges of ΓL(G) and gsd(G).
7

#### Elever resonerar om kommutativitet : En kvalitativ studie om hur elever resonerar kring och använder kommutativitet i addition / Students reason about commutativity : A qualitative study of students discussing and using commutativity in addition

Jansson, Malin January 2020 (has links)
8

#### Cognitive bases of spontaneous shortcut use in primary school arithmetic

Godau, Claudia 22 January 2015 (has links)
﻿Aufgabengeeignete Rechenstrategien flexibel zu nutzen ist ein wichtiges Ziel mathematischer Bildung und Bestandteil der Bildungsstandards der Grundschulmathematik. Kinder sollen spontan entscheiden, ob sie arithmetische Aufgaben in üblicher Weise berechnen oder ob sie Zeit und Aufwand investieren, um nach Vereinfachungsstrategien zu suchen und diese anzuwenden. Der Schwerpunkt der aktuellen Arbeit ist, wie Schüler beim flexiblen Erkennen und Anwenden von Vereinfachungsstrategien unterstützt werden können. Kontextfaktoren werden untersucht, welche die spontane Nutzung von Vereinfachungsstrategien unterstützen und den Transfer zwischen ihnen beeinflussen. Kognitive Theorien über die Entwicklung von mathematischen Konzepten und Strategien wurden mit Erkenntnissen aus der Expertise Forschung verbunden, welche die Unterschiede in der Flexibilität zwischen Experten und Novizen offen legen. Im Rahmen der iterativen Entwicklung von mathematischen Konzepten könnte ein erfolgreiches Erkennen und Anwenden einer Vereinfachungsstrategie von Faktoren, die konzeptionelles und/oder prozedurales Wissen aktivieren, profitieren. Am Beispiel von Vereinfachungsstrategien, die auf dem Kommutativgesetz (a + b = b + a) basieren, werden drei Kontextfaktoren (Instruktion, Assoziation und Schätzen), die spontanen Strategiegebrauch unterstützen oder behindern, untersucht. Insgesamt zeigt die Dissertation, dass spontane Strategienutzung durch bestimmte Kontextfaktoren unterstützt und durch Andere behindert werden kann. Diese Kontextfaktoren können im Prinzip in der Schulumgebung gesteuert werden. / Flexible use of task-appropriate solving strategies is an important goal in mathematical education and educational standard of elementary school mathematics. Children need to decide spontaneously whether they calculate arithmetic problems the usual way or whether they invest time and effort to search for shortcut options and apply them. The focus of the current work lies on how students can be supported in spotting and applying shortcut strategies flexibly. Contextual factors are investigated that support the spontaneous usage of shortcuts and influences the transfer between them. Cognitive theories about how mathematical concepts and strategies develop were combined with findings from research on expertise, which disclose differences between the flexibility of experts and novices. In line with iterativ development of mathematical concepts successfully spotting and applying a shortcut might thus benefit from factors activating conceptual and/or procedural knowledge. Shortcuts based on commutativity (a + b = b + a) are used as a test case to investigat three contextual factors (instruction, association and estimation), which support or hinder spontaneous strategy use. Overall, the dissertation shows that spontaneous strategy use can be supported by some contextual factors and impeded by others. These contextual factors can, in principle, be controlled in school environment.
9

#### Investigation into whether some key properties of BN under addition also apply in BN under multiplication and elaboration of some properties of the smallest ideal of a semigroup

Mweete, Kapaipi Hendrix 08 1900 (has links)
This dissertation will seek to explore if the properties of some of the key results on semigroups and their compacti cations under the operation of addition also apply under the operation of multiplication. Consider- able emphasis will be placed on the semigroup N of the set of natural numbers and its compacti cation N. Furthermore, the dissertation will discuss the smallest ideal of a semi- group and highlight some of its fundamental properties. / Mathematics / M. Sc. (Mathematics)
10

#### Strengthening the heart of an SMT-solver : Design and implementation of efficient decision procedures

Iguernelala, Mohamed 10 June 2013 (has links) (PDF)
This thesis tackles the problem of automatically proving the validity of mathematical formulas generated by program verification tools. In particular, it focuses on Satisfiability Modulo Theories (SMT): a young research topic that has seen great advances during the last decade. The solvers of this family have various applications in hardware design, program verification, model checking, etc.SMT solvers offer a good compromise between expressiveness and efficiency. They rely on a tight cooperation between a SAT solver and a combination of decision procedures for specific theories, such as the free theory of equality with uninterpreted symbols, linear arithmetic over integers and rationals, or the theory of arrays.This thesis aims at improving the efficiency and the expressiveness of the Alt-Ergo SMT solver. For that, we designed a new decision procedure for the theory of linear integer arithmetic. This procedure is inspired by Fourier-Motzkin's method, but it uses a rational simplex to perform computations in practice. We have also designed a new combination framework, capable of reasoning in the union of the free theory of equality, the AC theory of associative and commutativesymbols, and an arbitrary signature-disjoint Shostak theory. This framework is a modular and non-intrusive extension of the ground AC completion procedure with the given Shostak theory. In addition, we have extended Alt-Ergo with existing decision procedures to integrate additional interesting theories, such as the theory of enumerated data types and the theory of arrays. Finally, we have explored preprocessing techniques for formulas simplification as well as the enhancement of Alt-Ergo's SAT solver.

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