Thesis (M. Arch.)--University of Hong Kong, 1997. / Includes special report study entitled: Designing urban plaza and square. Includes bibliographical references.

Thesis (Ph. D.)--York University, 2000. / Typescript. Includes bibliographical references (leaves [328]-346). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pNQ59150.

This dissertation is devoted to theoretical studies of strongly interacting one-dimensional and quasi one-dimensional electron systems. The properties of one-dimensional electron systems can be studied within the bosonization technique, which presents fermions as collective bosonic density excitations. The power of this approach is the ability to treat electron-electron interaction exactly in the low-energy limit. The approach predicts the failure of Fermi liquid and an absence of long-range order in one-dimensions. The low-energy description of one-dimensional interacting systems is called the Tomonaga-Luttinger liquid theory. For example, the edges of quantum Hall systems are one-dimensional and described by a chiral Tomonaga-Luttinger liquid. Another example is a quantum spin Hall system with helical edge states, which are also described by a Tomonaga-Luttinger liquid. In our first work, a study of magnetized edge states of quantum spin-Hall system is presented. A magnetic field dependent signature of such edges is obtained, which can be verified in a Coulomb drag experiment. The second part of the dissertation is devoted to quasi-one dimensional antiferromagnetic lattices. A spatially anisotropic lattice antiferromagnet can be viewed as an array of one dimensional spin chains coupled in a way to match the lattice symmetry. This allows to use the non-Abelian bosonization technique to describe the low-energy physics of spin chains and study the inter-chain interactions perturbatively. The work presented in the dissertation studies the effect of Dzyaloshinskii-Moriya interaction on the magnetic phase diagram of the spatially anisotropic kagome antiferromagnet. We predict a Dzyaloshinskii-Moriya interaction driven phase transition from Neel to Neel+dimer state. In the third work, a novel model of the fractional quantum Hall effect is given. Wave functions of two-dimensional electrons in strong and quantizing magnetic field are essentially one-dimensional. That invites one to use the one-dimensional phenomenological bosonization to describe the density fluctuations of the two-dimensional interacting electrons in magnetic field. Remarkably, the constructed trial bosonized fermion operator describing the electron states with a fixed Landau gauge momentum is effectively two-dimensional. / text

In this thesis we discuss quantum Hall effects in bilayer graphene and other novel two-dimensional electron systems, focusing on the interplay between nontrivial Fermi surface topology and electron-electron interactions. In the first chapter I will give a brief introduction to some aspects of the quantum Hall effects. The second chapter discusses the physics in bilayer graphene in the absence of external magnetic fields. The first half discusses the band gap opening and trigonal warping effects in its bandstructure, and the second half focuses on the insulating ground state that results from electron-electron interactions. The third chapter discusses the single-particle Landau level structure in bilayer graphene. We will see that when both the band gap and trigonal warping effects are present, the highest Landau level in the valence band is three-fold degenerate at small magnetic fields. As the field increases, the three fold degeneracy is lifted and the Landau level structure gradually reduces to that in the absence of trigonal warping effects. At the end of the chapter we will demonstrate a formalism to map the momentum distribution of the single-particle Landau level structure. Such a mapping will give valuable information about the single-particle bandstructure. The fourth chapter deals with electron-electron interactions in the integer quantum Hall regime, where there is no fractional filling of the orbital degrees of freedom. In such a regime, the effect of electron-electron interactions often leads to spontaneous ordering of the internal degrees of freedom, such as spin, layer and valley. The first part of the chapter will establish the general formalism of Hartree-Fock theory in the quantum Hall regime, and then a specific theory for gapped bilayer graphene with trigonal warping effects is constructed. The resulting ground states are analyzed in the last part of the chapter. / text

When electrons are confined to a two dimensional layer with a perpendicular applied magnetic field, such that the ratio of electrons to flux quanta \((\nu)\) is a small integer or simple rational value, these electrons condense into remarkable new phases of matter that are strikingly different from the metallic electron gas that exists in the absence of a magnetic field. These phases, called integer or fractional quantum Hall (IQH or FQH) states, appear to be conventional insulators in their bulk, but behave as a dissipationless metal along their edge. Furthermore, electrical measurements of such a system are largely insensitive to the detailed geometry of how the system is contacted or even how large the system is... only the order in which contacts are made appears to matter. This insensitivity to local geometry has since appeared in a number of other two and three dimensional systems, earning them the classification of "topological insulators" and prompting an enormous experimental and theoretical effort to understand their properties and perhaps manipulate these properties to create robust quantum information processors. The focus of this thesis will be two experiments designed to elucidate remarkable properties of the metallic edge and insulating bulk of certain FQH systems. To study such systems, we can use mesoscopic devices known as single electron transistors (SETs). These devices operate by watching single electrons hop into and out of a confining box and into a nearby wire (for measurement). If it is initially unfavorable for an electron to leave the box, it can be made favorable by bringing another charge nearby, modifying the energy of the confined electron and pushing it out of the box and into the nearby wire. In this way, the SET can measure nearby charges. Alternatively, we can heat up the nearby wire to make it easier for electrons to enter and leave the box. In this way, the SET is a sensitive thermometer. First, by operating the SET as an electrometer, we measure the local charge of the \(\nu = 5/2\) FQH state. An immediate consequence of measuring fractionally quantized conductance plateaus is that the charge of local excitations should be a fraction of \(e\), the charge of an electron. The simplest charge that would be expected at \(\nu = 5/2\) would \(e/2\). However, if the charged particles that condense into the \(\nu = 5/2\) FQH state are paired, the expected local charge becomes \(e/4\). By watching these local charges being added to compressible puddles at \(\nu = 5/2\) and \(\nu = 5/7\), we find that the local charge at \(\nu = 5/2\) is indeed \(e/4\), indicating that objects of charge \(e\) are pairing to form the ground state of the system. This has implications for the future possibility of detecting non-Abelian braiding statistics in this state, and is described in detail in Chapter 2. By further monitoring how eagerly these \(e/4\) particles enter puddles as we increase the temperature, we can attempt to identify the presence of some excess entropy related to an unconventional degeneracy of their ground state. Such an entropy would be expected if the \(\nu = 5/2\) state exhibited non-Abelian braiding statistics. Progress on these experiments and prospects for building a quantum computer are presented in Chapter 3. Next, by operating the SET as a thermometer, we monitor heat flow along the compressible edge and through the bulk of IQH and FQH states. As an edge is heated and charge on that edge is swept downstream by the external magnetic field, we expect that charge to carry the injected energy in the same downstream direction. However, for certain FQH states, this is not the case. By heating an edge with a quantum point contact (QPC) and monitoring the heat transported upstream and downstream, we find that heat can be transported upstream when the edge contains structure related to \(\nu = 2/3\) FQH physics. Surprisingly, this can be present even when the bulk is in a conventional insulating (IQH) state. Additionally, we unexpectedly find that the \(\nu = 1\) bulk is capable of transporting heat, while the \(\nu = 2\) and \(\nu = 3\) bulk are not. These experiments are presented in Chapter 4. Finally, in Chapter 5, we describe preliminary work on a very different type of topological material, the quantum spin Hall (QSH) insulator. Here, the spin of electrons takes the place of the external magnetic field, creating edge states that propagate in both directions. Each of these edges behaves as an ideal one-dimensional mode, with predicted resistance \(h/e^2\). By creating well-defined regions where these modes can exist, we identify and characterize the conductance associated with topological edges. / Physics

No description available.

As National Collegiate Athletic Association (NCAA) Division I student-athletes arrive on college campuses, many often struggle in transitioning to the rigors of college academics and social life. To aid in this transition from high school to college, Division I athletic departments often utilize peer-mentor study hall programs, where incoming student-athletes work with non-athlete undergraduate and graduate master students to develop academic, study, and time management skills necessary for college success. The purpose of this study was to evaluate how the thoughts and feelings about the purpose and outcome of study hall differed across the expert/novice spectrum. How do student-athletes, peer mentors, and academic support staff perceive the purpose of study hall? What is the expected outcome of study hall? These questions will be explored and the varying array of results presented in a discussion that will illuminate the differences between expert and novice perceptions regarding study hall.

This paper discusses the ways in which Hofstede’s model of ‘dimensions of (‘national’) culture’ – and similar models developed in a functionalist paradigm – are problematically used to classify people. It briefly surveys critiques of Hofstede’s research method, but focusses on the dangers of attempting to develop models of culture within a functionalist paradigm. Although such models may be parsimonious and rapidly applied, I argue that they are a poor fit for CATaC investigations of the dynamic and reciprocal interactions between human cultures and technology. Instead, I contend, we must abandon this paradigm, and embrace methodologies that permit meaningfully explorations of the multiple and dynamic conditions influencing the field of cultural practices in human societies. I discuss the merits of ‘articulation’ as theory and method, and offer Hacking’s theory of “dynamic nominalism” as one example.

The project is a new city hall for the city of Lethbridge, Alberta, intended to replace the current building which was outgrown over twenty years ago, forcing several departments and city council to be housed in separate buildings. Past proposals for a new city hall have been confined to the current location in the Civic Centre, located on the periphery of the central business district. The primary objective of this project, however, was to create a city hall that was a successful public building, functioning not only as a setting for civic functions and ceremonies, but also as a place of everyday gatherings and activities that would contribute to the vitality of the city. For this reason a site was chosen downtown, on a block across from Gait Gardens, a park that at one time was the early coal mining settlement's town square. Once the commercial centre of the city, the blocks around Gait Gardens contain many heritage buildings, including the original city hall building. As retail activity moved to other locations the area and the park went into general decline. The block chosen as the site was cleared in 1965 and is currently occupied by a supermarket and a parking lot. In recent years the City of Lethbridge has made plans to reestablish Gait Gardens as the heart of the downtown area. Part of this strategy includes a radical redesign of the park itself which destroys much of its original formal plan. Locating an important public building, like City Hall, adjacent to the park would be a positive contribution to the revival of the area. City offices wrap around a wind-sheltered courtyard and large interior public space in order to fill up the block and to allow the building to come out to the street. The original twenty-five foot lot lines that ran east-west across the site govern the location and dimensions of major building elements. A tower, housing chimes and wind driven panels, marks the ceremonial entrance facing the park. A restaurant and small retail outlet are located along the west side of the building to support activity outside city hall hours. The southeast corner of Gait Gardens is redesigned to become a public plaza. Its main feature is a square reflecting pool and skating rink that corresponds exactly to the dimensions of the city hall courtyard. The park otherwise retains its original character and layout.

Detailed magnetometry and polarized neutron reflectometry studies were conducted on MnSi thin films grown epitaxially on Si(111) substrates. It is demonstrated that with an in-plane applied field H || [110], a broadly stable skyrmion phase exists at elevated temperatures and fields. Magnetometry and transport measurements with an out-of-plane applied field H || [111] prove that no skyrmion phase exists in this geometry. However, Hall effect measurements in this geometry show unexpected evidence of a topological Hall effect. This can be explained with a multi-dimensionally modulated cone phase, which proves that contrary to recent literature, a topological Hall effect is not sufficient proof of skyrmions. The results of this thesis represent a significant step towards a technologically relevant material in which skyrmions are broadly stable. A material of this type could be used in novel magnetic storage devices and signi ficantly impact our future computing capabilities.