Diagrammatic perturbation theory and the pseudogap

We study a model of quasiparticles on a two-dimensional square lattice coupled to Gaussian distributed dynamical fields. The model describes quasiparticles coupled to spin or charge fluctuations and is solved by a Monte Carlo sampling of the molecular field distributions. The non-perturbative solution is compared to various approximations based on diagrammatic perturbation theory. When the molecular field correlations are sufficiently weak, the diagrammatic calculations capture the qualitative aspects of the quasiparticle spectrum. For a range of model parameters near the magnetic boundary, we find that the quasiparticle spectrum is qualitatively different from that of a Fermi liquid in that it shows a double peak structure, and that the diagrammatic approximations we consider fail to reproduce, even qualitatively, the results of the Monte Carlo calculations. This suggests that the pseudogap induced by a coupling to antiferromagnetic fluctuations and the spin-splitting of the quasiparticle peak induced by a coupling to ferromagnetic spin-fluctuations lie beyond diagrammatic perturbation theory

Locally critical point in an anisotropic Kondo lattice

We report the first numerical identification of a locally quantum critical point, at which the criticality of the local Kondo physics is embedded in that associated with a magnetic ordering. We are able to numerically access the quantum critical behavior by focusing on a Kondo-lattice model with Ising anisotropy. We also establish that the critical exponent for the q-dependent dynamical spin susceptibility is fractional and compares well with the experimental value for heavy fermions.Comment: 4 pages, 3 figures; published versio

A Three-Dimensional Solution of Flows over Wings with Leading-Edge Vortex Separation. Part 2: Program Description Document

For abstract, see N75-32026

Reply to the comment by Carmelo Anile on the paper "Complexity analysis of the cerebrospinal fluid pulse waveform during infusion studies"

Veterinary technology is an emerging profession within the veterinary and allied animal health fields in Australia and affords graduates the opportunity to contribute to the small but growing body of literature within this discipline. This study describes the introduction of a contextualised assessment task to develop students’ research capability, competence and confidence in professional writing, and to engage them with the academic publishing process. Students worked in self-selected dyads to author a scientific case report, of publishable standard, based on authentic cases from their clinical practicum. Intrinsic to the task, students attended a series of workshops that explored topics such as critiquing the literature, professional writing styles and oral presentation skills. Assessment was multi-staged with progressive feedback, including peer review, and culminated with students presenting their abstracts at a mock conference. Students reported the task to be an enjoyable and valuable learning experience which improved their competence and confidence in scientific writing; supported by a comparison of previously submitted work. Linking scientific writing skills to clinical practice experiences enhanced learning outcomes and may foster the professionalisation of students within this emerging discipline

Magnetic latitude effects in the solar wind

The Weber-Davis model of the solar wind is generalized to include the effects of latitude. The principal assumptions of high electrical conductivity, rotational symmetry, the polytropic relation between pressure and density, and a flow-alined field in a system rotating with the sun, are retained. An approximate solution to the resulting equations for spherical boundary conditions at the base of the corona indicates a small component of latitudinal flow toward the solar poles at large distances from the sun as result of latitudinal magnetic forces

Vacuum Decay in Theories with Symmetry Breaking by Radiative Corrections

The standard bounce formalism for calculating the decay rate of a metastable vacuum cannot be applied to theories in which the symmetry breaking is due to radiative corrections, because in such theories the tree-level action has no bounce solutions. In this paper I derive a modified formalism to deal with such cases. As in the usual case, the bubble nucleation rate may be written in the form $A e^{-B}$. To leading approximation, $B$ is the bounce action obtained by replacing the tree-level potential by the leading one-loop approximation to the effective potential, in agreement with the generally adopted {\it ad hoc} remedy. The next correction to $B$ (which is proportional to an inverse power of a small coupling) is given in terms of the next-to-leading term in the effective potential and the leading correction to the two-derivative term in the effective action. The corrections beyond these (which may be included in the prefactor) do not have simple expressions in terms of the effective potential and the other functions in the effective action. In particular, the scalar-loop terms which give an imaginary part to the effective potential do not explicitly appear; the corresponding effects are included in a functional determinant which gives a manifestly real result for the nucleation rate.Comment: 39 pages, CU-TP-57

Local Moments in an Interacting Environment

We discuss how local moment physics is modified by the presence of interactions in the conduction sea. Interactions in the conduction sea are shown to open up new symmetry channels for the exchange of spin with the localized moment. We illustrate this conclusion in the strong-coupling limit by carrying out a Schrieffer Wolff transformation for a local moment in an interacting electron sea, and show that these corrections become very severe in the approach to a Mott transition. As an example, we show how the Zhang Rice reduction of a two-band model is modified by these new effects.Comment: Latex file with two postscript figures. Revised version, with more fully detailed calculation

Treatment and secondary prevention of venous thromboembolism in cancer

Patients with cancer who develop venous thromboembolism (VTE) are at elevated risk for recurrent thrombotic events, even during anticoagulant therapy. The clinical picture is further complicated because these patients are also at increased risk of bleeding while on anticoagulants. In general, there are four key goals of treatment for VTE: preventing fatal pulmonary embolism (PE); reducing short-term morbidities associated with acute leg or lung thrombus; preventing recurrent VTE; and preventing the long-term sequelae of VTE (e.g., post-thrombotic syndrome and chronic thromboembolic pulmonary hypertension). A fifth goal – minimising the risk for bleeding while on anticoagulation – is particularly warranted in patients with cancer. Traditionally, pharmacological treatment of VTE has two phases, with the transition between phases marked by a switch from a rapid-acting, parenterally administered anticoagulant (such as unfractionated heparin (UFH), low-molecular-weight heparin (LMWH), or fondaparinux) to an oral vitamin K antagonist (e.g., warfarin). Recent clinical trials of established agents and the advent of new pharmacological options are changing this paradigm. Low-molecular-weight heparin continued for 6 months is more effective than warfarin in the secondary prevention of VTE in cancer patients without increasing the risk of bleeding and is now the preferred treatment option. Given the impact of VTE on short-term and long-term outcomes in patients with cancer, a group of health-care providers based in the United Kingdom gathered in London in 2009 to discuss recent data on cancer-associated thrombosis and to evaluate how these recommendations can be integrated or translated into UK clinical practice. This article, which is the third of four articles covering key topics in cancer thrombosis, focuses on treatment and secondary prevention of VTE in cancer patients

New measure of electron correlation

We propose to quantify the "correlation" inherent in a many-electron (or many-fermion) wavefunction by comparing it to the unique uncorrelated state that has the same single-particle density operator as it does.Comment: Final version to appear in PR