Ising Model on a random network with annealed or quenched disorder

We study the equilibrium properties of an Ising model on a disordered random network where the disorder can be quenched or annealed. The network consists of four-fold coordinated sites connected via variable length one-dimensional chains. Our emphasis is on nonuniversal properties and we consider the transition temperature and other equilibrium thermodynamic properties, including those associated with one dimensional fluctuations arising from the chains. We use analytic methods in the annealed case, and a Monte Carlo simulation for the quenched disorder. Our objective is to study the difference between quenched and annealed results with a broad random distribution of interaction parameters. The former represents a situation where the time scale associated with the randomness is very long and the corresponding degrees of freedom can be viewed as frozen, while the annealed case models the situation where this is not so. We find that the transition temperature and the entropy associated with one dimensional fluctuations are always higher for quenched disorder than in the annealed case. These differences increase with the strength of the disorder up to a saturating value. We discuss our results in connection to physical systems where a broad distribution of interaction strengths is present.Comment: 11 pages including 9 figures. To appear in Phys. Rev.

Hydrodynamics of compressible superfluids in confined geometries

We present a study of the hydrodynamics of compressible superfluids in confined geometries. We use a perturbative procedure in terms of the dimensionless expansion parameter $(v/v_s)^2$ where $v$ is the typical speed of the flow and $v_s$ the speed of sound. A zero value of this parameter corresponds to the incompressible limit. We apply the procedure to two specific problems: the case of a trapped superfluid with a gaussian profile of the local density, and that of a superfluid confined in a rotating obstructed cylinder. We find that the corrections due to finite compressibility which are, as expected, negligible for liquid He, are important but amenable to the perturbative treatment for typical ultracold atomic systems.Comment: 17 pages, including 7 figures. To appear in Journ. Phys.

Superfluid Field response to Edge dislocation motion

We study the dynamic response of a superfluid field to a moving edge dislocation line to which the field is minimally coupled. We use a dissipative Gross-Pitaevskii equation, and determine the initial conditions by solving the equilibrium version of the model. We consider the subsequent time evolution of the field for both glide and climb dislocation motion and analyze the results for a range of values of the constant speed $V_D$ of the moving dislocation. We find that the type of motion of the dislocation line is very important in determining the time evolution of the superfluid field distribution associated with it. Climb motion of the dislocation line induces increasing asymmetry, as function of time, in the field profile, with part of the probability being, as it were, left behind. On the other hand, glide motion has no effect on the symmetry properties of the superfluid field distribution. Damping of the superfluid field due to excitations associated with the moving dislocation line occurs in both cases.Comment: 10 pages 7 figures. To appear in Phys. Rev

Dislocation Mobility and Anomalous Shear Modulus Effect in 4^4He Crystals

We calculate the dislocation glide mobility in solid $^4$He within a model that assumes the existence of a superfluid field associated with dislocation lines. Prompted by the results of this mobility calculation, we study within this model the role that such a superfluid field may play in the motion of the dislocation line when a stress is applied to the crystal. To do this, we relate the damping of dislocation motion, calculated in the presence of the assumed superfluid field, to the shear modulus of the crystal. As the temperature increases, we find that a sharp drop in the shear modulus will occur at the temperature where the superfluid field disappears. We compare the drop in shear modulus of the crystal arising from the temperature dependence of the damping contribution due to the superfluid field, to the experimental observation of the same phenomena in solid $^4$He and find quantitative agreement. Our results indicate that such a superfluid field plays an important role in dislocation pinning in a clean solid $^4$He at low temperatures and in this regime may provide an alternative source for the unusual elastic phenomena observed in solid $^4$He.Comment: 17 pages, 2 figures. To appear in JLT

Configurations of control: An exploratory analysis

© 2015 Elsevier Ltd. There is growing interest in how management controls operate together as a package of interrelated mechanisms. Although theoretical debate dates back to the seminal paper of Otley (1980), there remains little empirical analysis of how control mechanisms combine. To increase knowledge in this area this study explores how multiple accounting and other control mechanisms commonly combine and the associations these combinations have with firm context. From a cross-sectional sample of 400 firms, this study presents an empirically derived taxonomy of five control configurations used by top managers, labelled as simple, results, action, devolved, and hybrid. Many of these patterns closely resemble control configurations common to the literature, while others represent distinctively contemporary arrangements, such as flexible variants of traditional bureaucracy (action), and instances where multiple and seemingly conflicting control types intermesh (hybrid). In analyzing these configurations this study provides accounting and control researchers with empirical observations to refine and extend existing control frameworks and theory

Budget participation and budget emphasis in low uncertainty conditions - Considering alternative reasons to budget

This case study investigates how lower budget participation may be better suited to firms with a high budget emphasis, in lower uncertainty conditions. The organisation studied generates greater benefits when budget participation is low, though it has a high budget emphasis. This result is opposite to that found in Lau, et.al. (1995). The reason for this difference is shown to arise because budget emphasis in the case firm is not primarily related to performance evaluation as defined in prior budget research (Hopwood, 1972). Instead, the main reason for budgeting is operational planning (Hansen and Van der Stede, 2003), and this difference is shown to lead to the opposing findings. When budgets are used primarily for operational planning, their relationships to organisational antecedents appear to be different than when used for performance evaluation

Management control effectiveness and strategy: An empirical analysis of packages and systems

© 2016 Elsevier Ltd. This study examines management control (MC) combinations that are effective in different strategic contexts through two related approaches - MC as a package and MC as a system. First, this study identifies how a set of MC practices combine (i.e. MC packages) to achieve effective control outcomes for firms operating in defender and prospector strategic contexts by applying fuzzy set qualitative comparative analysis (fsQCA). Using data from a survey of top managers the analysis reveals that there are multiple ways by which firms can effectively combine MC practices in a given strategic context. Furthermore, the analysis shows that not all MC practices found to be relevant in isolation are relevant when examined simultaneously as a package. Second, based on a comparison of effective MC packages this study examines interdependencies between MC practices (i.e. MC systems). Results show that in defender firms a diagnostic control use of accounting and mechanistic structural controls act as complements, while mechanistic structural controls and measure diversity act as substitutes. In prospector firms an interactive control use of accounting and organic structural controls are found to have complementary effects. These results indicate that the effectiveness of accounting control and structural control choices are determined not only by their fit with strategic context but also by how they fit with each other. This study also demonstrates how an understanding of MC packages can provide guidance for theory development and empirical analysis of MC systems

Organisational characteristics, alternative reasons to budget and two budget forms

This study examines contingency relationships between organisational characteristics and four alternative operational reasons to budget, across two budget forms (fixed budget and rolling forecasts). Furthering the work of Hansen and Van der Stede (2004), results show that contingency relationships between organisational characteristics and the importance of operational reasons to budget were different for performance evaluation reasons, in comparison to operational planning reasons

Balanced scorecard design and performance impacts: some Australian evidence

consideration to the use of performance measurement systems, notably the Balanced Scorecard (BSC). However, there has been limited empirical investigation into the particular benefits that result from the use of the BSC (Ittner and Larcker, 1998). This study empirically examines how the BSC has been applied in practice and whether different BSC designs result in varying performance outcomes. Data is from a cross sectional survey, which provided a sample of 92 Australian firms using BSC. It is hypothesised that the BSC provides greater benefits when 1) cause and effect logic is used between measures 2) nonfinancial measures are tied to compensation and 3) implemented at multiple levels within the organisation. Results support the first proposition, although cause and effect logic appears to be more important if the BSC is tied to compensation. These results are discussed, and implications for practice and future research are presented