Hydrodynamic theory of surface excitations of three-dimensional topological insulators

Edge excitations of a fractional quantum Hall system can be derived as surface excitations of an incompressible quantum droplet using one dimensional chiral bosonization. Here we show that an analogous approach can be developed to characterize surface states of three-dimensional time reversal invariant topological insulators. The key ingredient of our theory is the Luther's multidimensional bosonization construction.Comment: 4 pages, published versio

Acute hypoglycemia impairs executive cognitive function in adults with and without type 1 diabetes

OBJECTIVE: Acute hypoglycemia impairs cognitive function in several domains. Executive cognitive function governs organization of thoughts, prioritization of tasks, and time management. This study examined the effect of acute hypoglycemia on executive function in adults with and without diabetes. RESEARCH DESIGN AND METHODS: Thirty-two adults with and without type 1 diabetes with no vascular complications or impaired awareness of hypoglycemia were studied. Two hyperinsulinemic glucose clamps were performed at least 2 weeks apart in a single-blind, counterbalanced order, maintaining blood glucose at 4.5 mmol/L (euglycemia) or 2.5 mmol/L (hypoglycemia). Executive functions were assessed with a validated test suite (Delis-Kaplan Executive Function). A general linear model (repeated-measures ANOVA) was used. Glycemic condition (euglycemia or hypoglycemia) was the within-participant factor. Between-participant factors were order of session (euglycemia-hypoglycemia or hypoglycemia-euglycemia), test battery used, and diabetes status (with or without diabetes). RESULTS: Compared with euglycemia, executive functions (with one exception) were significantly impaired during hypoglycemia; lower test scores were recorded with more time required for completion. Large Cohen d values (>0.8) suggest that hypoglycemia induces decrements in aspects of executive function with large effect sizes. In some tests, the performance of participants with diabetes was more impaired than those without diabetes. CONCLUSIONS: Executive cognitive function, which is necessary to carry out many everyday activities, is impaired during hypoglycemia in adults with and without type 1 diabetes. This important aspect of cognition has not received previous systematic study with respect to hypoglycemia. The effect size is large in terms of both accuracy and speed

The massless Thirring model in spherical field theory

We use the massless Thirring model to demonstrate a new approach to non-perturbative fermion calculations based on the spherical field formalism. The methods we present are free from the problems of fermion doubling and difficulties associated with integrating out massless fermions. Using a non-perturbative regularization, we compute the two-point correlator and find agreement with the known analytic solution.Comment: 11 pages, 2 figures, journal versio

Teaching the hidden symmetry of the Kepler problem in relativistic quantum mechanics - from Pauli to Dirac electron

Hidden symmetry in Coulomb interaction is one of the mysterious problems of modern physics. Additional conserved quantities associated with extra symmetry govern wide variety of physics problems, from planetary motion till fine and hyperfine structures of atomic spectra. In this paper we present a simple derivation of hidden symmetry operator in relativistic quantum mechanics for the Dirac equation in the Coulomb field. We established that this operator may be reduced to the one introduced by Johnson and Lippmann. It is worthwhile to notice that this operator was discussed in literature very rarely and so is not known well among physicists and was omitted even in the recent textbooks on relativistic quantum mechanics and/or quantum electrodynamics.Comment: 5 page

Landslide-dammed paleolake perturbs marine sedimentation and drives genetic change in anadromous fish

Large bedrock landslides have been shown to modulate rates and processes of river activity by forming dams, forcing upstream aggradation of water and sediment, and generating catastrophic outburst floods. Less apparent is the effect of large landslide dams on river ecosystems and marine sedimentation. Combining analyses of 1-m resolution topographic data (acquired via airborne laser mapping) and field investigation, we present evidence for a large, landslide-dammed paleolake along the Eel River, CA. The landslide mass initiated from a high-relief, resistant outcrop which failed catastrophically, blocking the Eel River with an approximately 130-m-tall dam. Support for the resulting 55-km-long, 1.3-km^3 lake includes subtle shorelines cut into bounding terrain, deltas, and lacustrine sediments radiocarbon dated to 22.5 ka. The landslide provides an explanation for the recent genetic divergence of local anadromous (ocean-run) steelhead trout (Oncorhynchus mykiss) by blocking their migration route and causing gene flow between summer run and winter run reproductive ecotypes. Further, the dam arrested the prodigious flux of sediment down the Eel River; this cessation is recorded in marine sedimentary deposits as a 10-fold reduction in deposition rates of Eel-derived sediment and constitutes a rare example of a terrestrial event transmitted through the dispersal system and recorded offshore

HQET chromomagnetic interaction at two loops

We present the coefficient of the chromomagnetic interaction operator, the only unknown coefficient in the Heavy Quark Effective Theory (HQET) lagrangian up to the $1/m$ level, with the two-loop accuracy by matching scattering amplitudes of an on-shell heavy quark in an external field in full QCD and HQET, and obtain the two-loop anomalous dimension of this operator in HQET.Comment: 10 pages, LaTeX2e, 2 eps figures included. Revised discussion of (n_f-1)-flavour HQET include

Point-form quantum field theory and meson form factors

We shortly review point-form quantum field theory, i.e. the canonical quantization of a relativistic field theory on a Lorentz-invariant surface of the form $x_\mu x^\mu = \tau^2$. As an example of how point-form quantum field theory may enter the framework of relativistic quantum mechanics we discuss the calculation of the electromagnetic form factor of a confined quark-antiquark pair (e.g. the pion).Comment: 3 pages, 2 figures. Based on a talk presented by W. Schweiger at the 20th European Conference on Few-Body Problems in Physics, September 10-14 2007, Pisa, Ital

Unification of the Soluble Two-dimensional vector coupling models

The general theory of a massless fermion coupled to a massive vector meson in two dimensions is formulated and solved to obtain the complete set of Green's functions. Both vector and axial vector couplings are included. In addition to the boson mass and the two coupling constants, a coefficient which denotes a particular current definition is required for a unique specification of the model. The resulting four parameter theory and its solution are shown to reduce in appropriate limits to all the known soluble models, including in particular the Schwinger model and its axial vector variant.Comment: 10 page