Mazurkiewicz traces were introduced by A. Mazurkiewicz in 1977 as a language representation of partial orders to model "true concurrency". The theory of Mazurkiewicz traces has been utilised to tackle not only various aspects of concurrency theory but also problems from other areas, including combinatorics, graph theory, algebra, and logic. However, neither Mazurkiewicz traces nor partial orders can model the "not later than" relationship. In 1995, comtraces (combined traces) were introduced by Janicki and Koutny as a formal language counterpart to finite stratified order structures. They show that each comtrace uniquely determines a finite stratified order structure, yet their work contains very little theory of comtraces. This thesis aims at enriching the tools and techniques for studying the theory of comtraces. Our first contribution is to introduce the notions of absorbing monoids, generalised comtrace monoids, partially commutative absorbing monoids, and absorbing monoids with compound generators, all of which are the generalisations of Mazurkiewicz trace and comtrace monoids. We also define and study the canonical representations of these monoids. Our second contribution is to define the notions of non-serialisable steps and utilise them to study the construction which Janicki and Koutny use to build stratified order structures from comtraces. Moreover, we show that any finite stratified order structure can be represented by a comtrace. Our third contribution is to study the relationship between generalised comtraces and generalised stratified order structures. We prove that each generalised comtrace uniquely determines a finite generalised stratified order structure. / Thesis / Master of Computer Science (MCS)

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Thesis (M.Sc.) - Carleton University, 2005. / Includes bibliographical references (p. 61-63). Also available in electronic format on the Internet.

We present some results about chains of monoids S₀ → S₁ → S.₂. and their associated representation rings, with particular emphasis to behavior as the index n (viz. S_n) varies. A rich supply of such chains of monoids can be found via specializations of diagrammatic algebras or variations of diagrammatic algebras, where the inclusions involve the addition of loose strands. This thesis comprises of original results along three themes associated with the above: (1) Identifying a certain polynomial property featuring operators on representation rings, and a characterization of chains of groups G₀ →G₁ → G₂ .. which satisfy this polynomial property. (2) Understanding the induced action on homology from topological actions of the chain of Temperley-Lieb monoids TL₁ → TL₂ → TL₃ ... . Making the analogy to classical representation stability. (3) Identifying chains of diagrammatic monoids S₀ → S₁ → S₂ .. on which cryptographic protocols resist linear attacks. Explicitly computes lower bounds on the dimensions of all representations of various truncations of diagrammatic monoids.

An integral domain D is weakly integrally closed if whenever there is an element x in the quotient field of D and a nonzero finitely generated ideal J of D such that xJ J2, then x is in D. We define weakly integrally closed numerical monoids similarly. If a monoid algebra is weakly integrally closed, then so is the monoid. A pattern F of finitely many 0's and 1's is forbidden if whenever the characteristic binary string of a numerical monoid M contains F, then M is not weakly integrally closed. Any stretch of the pattern 11011 is forbidden. A numerical monoid M is weakly integrally closed if and only if it has a forbidden pattern. For every finite set S of forbidden patterns, there exists a monoid that is not weakly integrally closed and that contains no stretch of a pattern in S. It is shown that particular monoid algebras are weakly integrally closed. / by Mary E. Hopkins. / Thesis (Ph.D.)--Florida Atlantic University, 2009. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2009. Mode of access: World Wide Web.

In this thesis, we cover the general topic of state complexity. In particular, we examine the bounds on the state complexity of some different representations of regular languages. As well, we consider the state complexity of the operation root(<i>L</i>). We give quick treatment of the deterministic state complexity bounds for nondeterministic finite automata and regular expressions. This includes an improvement on the worst-case lower bound for a regular expression, relative to its alphabetic length. The focus of this thesis is the study of the increase in state complexity of a regular language <i>L</i> under the operation root(<i>L</i>). This operation requires us to examine the connections between abstract algebra and formal languages. We present results, some original to this thesis, concerning the size of the largest monoid generated by two elements. Also, we give good bounds on the worst-case state complexity of root(<i>L</i>). In turn, these new results concerning root(<i>L</i>) allow us to improve previous bounds given for the state complexity of two-way deterministic finite automata.

In this thesis, we cover the general topic of state complexity. In particular, we examine the bounds on the state complexity of some different representations of regular languages. As well, we consider the state complexity of the operation root(<i>L</i>). We give quick treatment of the deterministic state complexity bounds for nondeterministic finite automata and regular expressions. This includes an improvement on the worst-case lower bound for a regular expression, relative to its alphabetic length. The focus of this thesis is the study of the increase in state complexity of a regular language <i>L</i> under the operation root(<i>L</i>). This operation requires us to examine the connections between abstract algebra and formal languages. We present results, some original to this thesis, concerning the size of the largest monoid generated by two elements. Also, we give good bounds on the worst-case state complexity of root(<i>L</i>). In turn, these new results concerning root(<i>L</i>) allow us to improve previous bounds given for the state complexity of two-way deterministic finite automata.

Please refer to the thesis for the abstract. / Thesis (Ph.D.)-University of Natal, Durban, 1998.

Thesis (PhD)--Macquarie University (Division of Information & Communication Sciences, Dept. of Mathematics), 2007. / Thesis by publication. Bibliography: p. 119-123.

This thesis is divided into two parts. The first part is concerned with the commutative algebra of certain combinatorial structures arising from uniform hypergraphs. The main focus lies on two particular classes of hypergraphs called chordal hypergraphs and complete hypergraphs, respectively. Both these classes arise naturally as generalizations of the corresponding well known classes of simple graphs. The classes of chordal and complete hypergraphs are introduced and studied in Chapter 2 and Chapter 3 respectively. Chapter 4, that is the content of \cite{E5}, answers a question posed at the P.R.A.G.MAT.I.C. summer school held in Catania, Italy, in 2008. In Chapter 5 we study hypergraph analogues of line graphs and cycle graphs. Chapter 6 is concerned with a connectedness notion for hypergraphs and in Chapter 7 we study a weak version of shellability.The second part is concerned with affine monoids and their monoid rings. Chapter 8 provide a combinatorial study of a class of positive affine monoids that behaves in some sense like numerical monoids. Chapter 9 is devoted to the class of numerical monoids of maximal embedding dimension. A combinatorial description of the graded Betti numbers of the corresponding monoid rings in terms of the minimal generators of the monoids is provided. Chapter 10 is concerned with monomial subrings generated by edge sets of complete hypergraphs.