Lattice Discretization in Quantum Scattering

The utility of lattice discretization technique is demonstrated for solving nonrelativistic quantum scattering problems and specially for the treatment of ultraviolet divergences in these problems with some potentials singular at the origin in two and three space dimensions. This shows that lattice discretization technique could be a useful tool for the numerical solution of scattering problems in general. The approach is illustrated in the case of the Dirac delta function potential.Comment: 9 page

Humans decompose tasks by trading off utility and computational cost

Human behavior emerges from planning over elaborate decompositions of tasks into goals, subgoals, and low-level actions. How are these decompositions created and used? Here, we propose and evaluate a normative framework for task decomposition based on the simple idea that people decompose tasks to reduce the overall cost of planning while maintaining task performance. Analyzing 11,117 distinct graph-structured planning tasks, we find that our framework justifies several existing heuristics for task decomposition and makes predictions that can be distinguished from two alternative normative accounts. We report a behavioral study of task decomposition ($N=806$) that uses 30 randomly sampled graphs, a larger and more diverse set than that of any previous behavioral study on this topic. We find that human responses are more consistent with our framework for task decomposition than alternative normative accounts and are most consistent with a heuristic -- betweenness centrality -- that is justified by our approach. Taken together, our results provide new theoretical insight into the computational principles underlying the intelligent structuring of goal-directed behavior

Linear Response Calculations of Spin Fluctuations

A variational formulation of the time--dependent linear response based on the Sternheimer method is developed in order to make practical ab initio calculations of dynamical spin susceptibilities of solids. Using gradient density functional and a muffin-tin-orbital representation, the efficiency of the approach is demonstrated by applications to selected magnetic and strongly paramagnetic metals. The results are found to be consistent with experiment and are compared with previous theoretical calculations.Comment: 11 pages, RevTex; 3 Figures, postscript, high-resolution printing (~1200dpi) is desire

Quasiparticle band structure of infinite hydrogen fluoride and hydrogen chloride chains

We study the quasiparticle band structure of isolated, infinite HF and HCl bent (zigzag) chains and examine the effect of the crystal field on the energy levels of the constituent monomers. The chains are one of the simplest but realistic models of the corresponding three-dimensional crystalline solids. To describe the isolated monomers and the chains, we set out from the Hartree-Fock approximation, harnessing the advanced Green's function methods "local molecular orbital algebraic diagrammatic construction" (ADC) scheme and "local crystal orbital ADC" (CO-ADC) in a strict second order approximation, ADC(2,2) and CO-ADC(2,2), respectively, to account for electron correlations. The configuration space of the periodic correlation calculations is found to converge rapidly only requiring nearest-neighbor contributions to be regarded. Although electron correlations cause a pronounced shift of the quasiparticle band structure of the chains with respect to the Hartree-Fock result, the bandwidth essentially remains unaltered in contrast to, e.g., covalently bound compounds.Comment: 11 pages, 6 figures, 6 tables, RevTeX4, corrected typoe

The influence of lower-limb prostheses technology on Paracanoeing time-trial performance

Within the Paracanoeing discipline, it is important to ensure appropriate control is achieved by a paddler with a disability. However, this Paralympic Games discipline has seen very little attention to date. The aims of this study were to understand the kinematic impact to a paracanoeist when not utilising the use of a prosthetic lowerlimb. A kayaker with a uni-lateral transfemoral amputation completed several 200m maximal efforts both with and without their prosthesis. When the prosthetic limb was removed, there were significant differences found in stroke rate, stroke speed, stroke length and overall power output. Sagittal and frontal video analysis demonstrated the residual limb movements when paddling and indicated where support would be required to improve the kayak’s control. It is recommended that those with lower-limb absence wishing to paddle a kayak competitively utilise the use of a prostheses designed for the kayaking environment that supports the residual limb at both the upper and inner thigh and the distal end

Exploring the hierarchical structure of human plans via program generation

Human behavior is inherently hierarchical, resulting from the decomposition of a task into subtasks or an abstract action into concrete actions. However, behavior is typically measured as a sequence of actions, which makes it difficult to infer its hierarchical structure. In this paper, we explore how people form hierarchically-structured plans, using an experimental paradigm that makes hierarchical representations observable: participants create programs that produce sequences of actions in a language with explicit hierarchical structure. This task lets us test two well-established principles of human behavior: utility maximization (i.e. using fewer actions) and minimum description length (MDL; i.e. having a shorter program). We find that humans are sensitive to both metrics, but that both accounts fail to predict a qualitative feature of human-created programs, namely that people prefer programs with reuse over and above the predictions of MDL. We formalize this preference for reuse by extending the MDL account into a generative model over programs, modeling hierarchy choice as the induction of a grammar over actions. Our account can explain the preference for reuse and provides the best prediction of human behavior, going beyond simple accounts of compressibility to highlight a principle that guides hierarchical planning

Can a strongly interacting Higgs boson rescue SU(5)?

Renormalization group analyses show that the three running gauge coupling constants of the Standard Model do not become equal at any energy scale. These analyses have not included any effects of the Higgs boson's self-interaction. In this paper, I examine whether these effects can modify this conclusion.Comment: 8 pages (plus 4 postscript figures

Axis Specific Player Load to Quantify Lower Limb Biomechanical Loading in Adolescent Badminton Players

While the use of accelerometer derived Player Load has become increasingly prominent, the limitation of this approach is that training load is reduced to a single number with no differentiation between the mechanisms of loading, resulting in a loss of context. As recovery from different loadings occur at different rates, the inability to differentiate between the loading mechanisms could lead to under or over training in one or more of these mechanisms. This study sought to compare axis specific accelerometer derived Player Load with differential RPE scores to establish a means of quantifying the lower limb biomechanical load of adolescent badminton training, to try and understand some of the context into the Player Load number. It was postulated that the Player Load from the vertical axis would provide a more precise measure of lower limb loading as other loading parameters, such as upper body rotation observed during a smash, would be removed from the calculation. Nineteen adolescent badminton players (Age: 14.0 ± 0.8 y) based at a dedicated high performance youth training environment wore a GPS-embedded accelerometer between the scapulae in a purpose built vest during court-based training. After each training session the participants provided two RPE scores, one localised for the legs and one for breathlessness. Overall low correlations were observed between the Player Load and RPE values. The Player Load for the vertical axis showed a stronger correlation with the RPE for breathlessness than the RPE for the lower limb stress. The results from this study suggest that axis specific Player Load from the vertical axis does not provide greater insight into lower-limb biomechanical load compared to overall Player Load in adolescent badminton players

Optimization of Monte-Carlo calculations of the effective potential

We study Monte Carlo calculations of the effective potential for a scalar field theory using three techniques. One of these is a new method proposed and tested for the first time. In each case we extract the renormalised quantities of the theory. The system studied in our calculations is a one component $\phi^4$ model in two dimensions. We apply these methods to both the weak and strong coupling regime. In the weak coupling regime we compare our results for the renormalised quantities with those obtained from two-loop lattice perturbation theory. Our results are verified in the strong coupling regime through comparison with the strong coupling expansion. We conclude that effective potential methods, when suitably chosen, can be accurate tools in calculations of the renormalised parameters of scalar field theories.Comment: 26 pages of LaTeX, uses psfig.sty with 6 figures. Entire manuscript available as a postscript file via WWW at http://www.physics.adelaide.edu.au/theory/papers/ADP-97-13.T250-abs.html or via anonymous ftp at ftp://bragg.physics.adelaide.edu.au/pub/theory/ADP-97-13.T250.p