Spin and energy correlations in the one dimensional spin 1/2 Heisenberg model

In this paper, we study the spin and energy dynamic correlations of the one dimensional spin 1/2 Heisenberg model, using mostly exact diagonalization numerical techniques. In particular, observing that the uniform spin and energy currents decay to finite values at long times, we argue for the absence of spin and energy diffusion in the easy plane anisotropic Heisenberg model.Comment: 10 pages, 3 figures, gzipped postscrip

Finite Temperature and Dynamical Properties of the Random Transverse-Field Ising Spin Chain

We study numerically the paramagnetic phase of the spin-1/2 random transverse-field Ising chain, using a mapping to non-interacting fermions. We extend our earlier work, Phys. Rev. 53, 8486 (1996), to finite temperatures and to dynamical properties. Our results are consistent with the idea that there are ``Griffiths-McCoy'' singularities in the paramagnetic phase described by a continuously varying exponent $z(\delta)$, where $\delta$ measures the deviation from criticality. There are some discrepancies between the values of $z(\delta)$ obtained from different quantities, but this may be due to corrections to scaling. The average on-site time dependent correlation function decays with a power law in the paramagnetic phase, namely $\tau^{-1/z(\delta)}$, where $\tau$ is imaginary time. However, the typical value decays with a stretched exponential behavior, $\exp(-c\tau^{1/\mu})$, where $\mu$ may be related to $z(\delta)$. We also obtain results for the full probability distribution of time dependent correlation functions at different points in the paramagnetic phase.Comment: 10 pages, 14 postscript files included. The discussion of the typical time dependent correlation function has been greatly expanded. Other papers of APY are available on-line at http://schubert.ucsc.edu/pete

Southern Rural Public Schools: A Study of Teacher Perspectives

This ethnography explores teachers’ perspectives of the cultural issues affecting academic performance in twelve public high schools in rural Mississippi and Louisiana. Fr om a thematic analysis of the tape-recorded interviews of forty-one mathematics teachers, five categories emerged, each comprising a qualitative aspect of teaching high school in an economically depressed area of the deep South: society, race, students, families, and schools. Each of these categories is discussed and explicated using exemplars from the interviews to show how each category emerged from the data. In addition, the relationships among these categories, which form a destructive cycle of poverty, low expectations, poor academic achievement, and inadequate opportunity, are discussed. Implications of this research for teachers and policy makers are explored

Reinvigorating Maneuver Warfare: An Organizational Learning Analysis of A Failed Strategic Initiative

ABSTRACT Reinvigorating Maneuver Warfare: An Organizational Learning Analysis of a Failed Strategic Initiative. by BP McCoy March 2020 Chair: Richard Baskerville Major Academic Unit: Executive Doctorate in Business The world is a dynamic and turbulent place. Organizations of all types regularly face the dual challenge of learning from the emerging realities of their environment and using that knowledge to accurately adapt to remain competitive. Often, the changes required to remain competitive demand a significant and irretrievable strategic investment of resources and changes in the status quo of how the organization will function going forward. Such strategic changes are often communicated in the form of mission or vision statements, campaign plans, or philosophies. Considering the resources committed and the opportunity costs involved, strategic initiatives must be implemented with care and precision to succeed, as a failed implementation could pose an existential threat to the organization. This case study examines one organization\u27s attempt and failure to sufficiently implement a strategic initiative. This study may be tailored and applied to any organization seeking the adaptive change necessary to succeed in the dynamic and contested environments of business or conflict. The study format is a cross-sectional single case study informed by the Theory of Action. The results of this study revealed five explanatory frames which serve to describe and explain the dynamics of the organization, and they illuminate the influence Model I single-loop and Model II double-loop organizational learning systems have on the implementation of a strategic initiative. Captured within the explanatory frames was the discovery of a surprising anomaly, namely the presence of a sub rosa clan. The sub rosa clan’s Model I behavioral control produced a bête noires[1] effect that countered the senior management’s Model II learning efforts, sustained the status quo, and sunk the strategic initiative. This study contributes to the organizational learning, maneuver warfare, and control theory literature streams and offers managers potential corrective interventions that may be applied proactively and preemptively to enable the successful implementation of a strategic initiative. Keywords: Organizational Learning, Theory of Action, Single-loop learning, Double-loop learning, Clans, Maneuver Warfare, Mission Command. [1] French; the literal translation is “black beast.” A bête noires is avoided by others. It may be a thing that is particularly dreadful

Domain wall dynamics of the Ising chains in a transverse field

We show that the dynamics of an Ising spin chain in a transverse field conserves the number of domains (strings of down spins in an up-spin background) at discrete times. This enables the determination of the eigenfunctions of the time-evolution operator, and the dynamics of initial states with domains. The transverse magnetization is shown to be identically zero in all sectors with a fixed number of domains. For an initial state with a single string of down spins, the local magnetization, the equal-time and double-time spin-spin correlation functions, are calculated analytically as functions of time and the initial string size. The domain size distribution function can be expressed as a simple integral involving Bessel functions.Comment: 4 pages with three figure

Use of in vitro and haptic assessments in the characterisation of surface lubricity

Lubricity is a key property of hydrophilic-coated urinary catheter surfaces. In vitro tests are commonly employed for evaluation of surface properties in the development of novel catheter coating technologies, however, their value in predicting the more subjective feeling of lubricity requires validation. We herein perform a range of in vitro assessments and human organoleptic studies to characterise surface properties of developmental hydrophilic coating formulations, including water wettability, coefficient of friction, dry-out kinetics and lubricity. Significant reductions of up to 40% in the contact angles and coefficient of friction values of the novel coating formulations in comparison to the control poly(vinyl pyrrolidone)-coated surfaces were demonstrated during quantitative laboratory assessments. In contrast, no significant differences in the more subjective feeling of lubricity between the novel formulations and the control-coated surfaces were observed when formulations were haptically assessed by the techniques described herein. This study, importantly, highlights the need for optimisation of in vitro and human haptic assessments to more reliably predict patient preferences