Topological Kondo Insulators

This article reviews recent theoretical and experimental work on a new class of topological material - topological Kondo insulators, which develop through the interplay of strong correlations and spin-orbit interactions. The history of Kondo insulators is reviewed along with the theoretical models used to describe these heavy fermion compounds. The Fu-Kane method of topological classification of insulators is used to show that hybridization between the conduction electrons and localized f-electrons in these systems gives rise to interaction-induced topological insulating behavior. Finally, some recent experimental results are discussed, which appear to confirm the theoretical prediction of the topological insulating behavior in Samarium hexaboride, where the long-standing puzzle of the residual low-temperature conductivity has been shown to originate from robust surface states.Comment: Accepted as an article in the Annual Review of Condensed Matter Physics, Volume 7 (2016

Two-fluid behavior of the Kondo lattice in the 1/N slave boson approach

It has been recently shown by Nakatsuji, Pines, and Fisk [S. Nakatsuji, D. Pines, and Z. Fisk, Phys. Rev. Lett. 92, 016401 (2004)] from the phenomenological analysis of experiments in Ce1-xLaxCoIn5 and CeIrIn5 that thermodynamic and transport properties of Kondo lattices below coherence temperature can be very successfully described in terms of a two-fluid model, with Kondo impurity and heavy electron Fermi liquid contributions. We analyze thermodynamic properties of Kondo lattices using 1/N slave boson treatment of the periodic Anderson model and show that these two contributions indeed arise below the coherence temperature. We find that the Kondo impurity contribution to thermodynamics corresponds to thermal excitations into the flat portion of the energy spectrum.Comment: 7 pages, 2 figure

Biodiesel: The Next Fuel?

The focus of this project is to research the environmental and economic benefits of biodiesel. The motivation for this project came from the question of: Does the cost of biodiesel justify the pollution reduction? Research had to be done to gain the facts and knowledge to support the cause. This includes finding possible sourcing, pros, cons, costs, fuel mixes, environmental, and mechanical information as it pertains to diesel engines and even the potential use in the CATbus fleet. Secondly, CATbus would have to be contacted in order to gain their thoughts and share the supporting information on biodiesel. The outcome of this project should show that environmental effects are better when using biodiesel versus regular petroleum diesel, and that there is less impact on human life. Our conclusion is that we recommend CATbus to use biodiesel over regular petroleum diesel. Thanks goes to our advisor Gary Gaulin and the Creative Inquiry program for making this project possible

LONGITUDINAL CHANGES IN THE NEUROMUSCULAR FUNCTION AMONG LAW ENFORCEMENT OFFICERS

Law enforcement officers (LEO) are crucial for public safety and perform physically demanding tasks in highly stressful and hazardous conditions. This project aimed to investigate longitudinal changes in neuromuscular function, a critical factor that influences both occupational performance and injury risk. We examined changes in physical activity, dietary habits, and neuromuscular function longitudinally (394.7 ± 22.2 days) in 50 LEO (age = 37.2 ± 10.1 yrs; BMI = 29.6 ± 6.6 kg/m2). Nineteen LEO completed follow-up testing and demonstrated significant improvements in balance for both legs (P≤0.04), but no significant changes in all other variables (P≥0.12). Although there were minimal longitudinal changes in neuromuscular function, the poor retention rates may have impacted these results. This study indicates the need for the development of retention strategies for future longitudinal studies to improve our understanding of changes in LEO health, neuromuscular function, and performance.Master of Art

Emergent Potts Order in a Coupled Hexatic-Nematic XY model

Addressing the nature of an unexpected smectic-A' phase in liquid crystal 54COOBC films, we perform large scale Monte Carlo simulations of a coupled hexatic-nematic XY model. The resulting finite-temperature phase diagram reveals a small region with composite Potts $\mathbb{Z}_3$ order above the vortex binding transition; this phase is characterized by relative hexatic-nematic ordering though both variables are disordered. The system develops algebraic hexatic and nematic order only at a lower temperature. This multi-step melting scenario agrees well with the experimental observations of a sharp specific heat anomaly that emerges above the onset of hexatic positional order. We therefore propose that the smectic-A' phase is characterized by composite Potts order and bound-states of fractional vortices.Comment: 22 pages, 10 figures, 1 tabl

Infra-red divergences in plane wave backgrounds

We show that the emission of soft photons via nonlinear Compton scattering in a pulsed plane wave (laser field) is in general infra-red divergent. We give examples of both soft and soft-collinear divergences, and we pay particular attention to the case of crossed fields in both classical and quantum theories.Comment: 15 pages, 7 figure