Magnetic properties of the Anderson model: a local moment approach

We develop a local moment approach to static properties of the symmetric Anderson model in the presence of a magnetic field, focussing in particular on the strong coupling Kondo regime. The approach is innately simple and physically transparent; but is found to give good agreement, for essentially all field strengths, with exact results for the Wilson ratio, impurity magnetization, spin susceptibility and related properties.Comment: 7 pages, 3 postscript figues. Latex 2e using the epl.cls Europhysics Letters macro packag

The Subcolonization and Buildup of \u3ci\u3eTetrastichus Julis,\u3c/i\u3e (Hymenoptera: Eulophidae) a Larval Parasitoid of the Cereal Leaf Beetle, (Coleoptera: Chrysomelidae) in the Lower Peninsula of Michigan

Following initial establishment of the parasitoid, Tetrastichus julis (Walker), at a carefully managed field nursery, releases of parasitized Oulema melanopus larvae were made by Michigan county agents at preselected sites throughout the lower peninsula during 1970-74. A follow-up recovery program during 1971-75 revealed continued dispersion and population increase for T. julis. An independent census verified the increasing rates of parasitism

Dynamics and transport properties of heavy fermions: theory

The paramagnetic phase of heavy fermion systems is investigated, using a non-perturbative local moment approach to the asymmetric periodic Anderson model within the framework of dynamical mean field theory. The natural focus is on the strong coupling Kondo-lattice regime wherein single-particle spectra, scattering rates, dc transport and optics are found to exhibit w/w_L,T/w_L scaling in terms of a single underlying low-energy coherence scale w_L. Dynamics/transport on all relevant (w,T)-scales are encompassed, from the low-energy behaviour characteristic of the lattice coherent Fermi liquid, through incoherent effective single-impurity physics likewise found to arise in the universal scaling regime, to non-universal high-energy scales; and which description in turn enables viable quantitative comparison to experiment.Comment: 27 pages, 12 figure

A comparison of wake characteristics of model and prototype buildings in transverse winds

Previously measured mean velocity and turbulence intensity profiles in the wake of a 26.8-m long building 3.2 m high and transverse to the wind direction in an atmospheric boundary layer several hundred meters thick were compared with profiles at corresponding stations downstream of a 1/50-scale model on the floor of a large meteorological wind tunnel in a boundary layer 0.61 m in thickness. The validity of using model wake data to predict full scale data was determined. Preliminary results are presented which indicate that disparities result from differences in relative depth of logarithmic layers, surface roughness, and the proximity of upstream obstacles

Finite temperature dynamics of the Anderson model

The recently introduced local moment approach (LMA) is extended to encompass single-particle dynamics and transport properties of the Anderson impurity model at finite-temperature, T. While applicable to arbitrary interaction strengths, primary emphasis is given to the strongly correlated Kondo regime (characterized by the T=0 Kondo scale $\omega_{\rm K}$). In particular the resultant universal scaling behaviour of the single-particle spectrum D(\omega; T) \equiv F(\frac{\w}{\omega_{\rm K}}; \frac{T}{\omega_{\rm K}}) within the LMA is obtained in closed form; leading to an analytical description of the thermal destruction of the Kondo resonance on all energy scales. Transport properties follow directly from a knowledge of $D(\omega; T)$. The $T / \omega_{\rm K}$-dependence of the resulting resistivity $\rho(T)$, which is found to agree rather well with numerical renormalization group calculations, is shown to be asymptotically exact at high temperatures; to concur well with the Hamann approximation for the s-d model down to $T/\omega_{\rm K} \sim 1$, and to cross over smoothly to the Fermi liquid form $\rho (T) - \rho (0) \propto -(T/\omega_{\rm K})^2$ in the low-temperature limit. The underlying approach, while naturally approximate, is moreover applicable to a broad range of quantum impurity and related models

Production of Entangled Photons via Spontaneous Parametric Down-Conversion

Quantum entanglement, a phenomenon in which the behavior of one particle is somehow immediately correlated with and informed by what is happening to a partner particle a long distance away, has been a pivotal part of the formulation of quantum theory as we know it today and is currently generating many promising avenues of research. As such, finding ways to reliably and inexpensively generate systems of entangled particles for research purposes has become crucial. For my project, I attempt to set up a system that generates energy- and polarization-entangled photons via a technique called spontaneous parametric down conversion. This method for generating entangled particles involves shooting a laser beam at a special type of nonlinear crystal. Most of the photons in the beam pass right through the crystal, but some are absorbed by it. An absorbed photon’s energy excites the crystal, which then releases that energy by emitting a pair of entangled photons. This occurs tens of thousands of times per second to create two streams of photons where each photon in one beam has an energy-entangled partner in the other. These photons can then be manipulated and employed in experimental examinations of a variety of quantum optical phenomena

Best Practices for Asphalt Emulsion Particle Size Analyses Using a Coulter Counter

As asphalt pavements develop distresses, pavement preservation, maintenance, and rehabilitation treatments are used to mitigate distresses and extend the life of the pavement. Many of these treatments utilize asphalt emulsion. Previous research has linked particle size to material properties including viscosity and storage stability. General statements have also been made about particle size influencing emulsion performance while other researchers have identified a trend between particle size and prime coat penetration. Even though literature discusses the importance of particle size, there is little guidance on the best practices of asphalt emulsion particle size analyses, specifically with a Coulter counter. Data collected from eight emulsions was analyzed, and a recommended procedure for testing and analyzing particle size results using a Coulter counter was produced in the form of a draft ASTM specification. RStudio was used to identify correlations between particle size parameters and the additional tests. It is recommended to create three samples for each emulsion being tested and to test each sample three times. Each test should count at least 5,000 particles and a cumulative particle volume of at least 70,000 μm3. To provide values representative of the emulsion, the runs should be averaged together to represent the samples, and the samples should be averaged together to represent the emulsion. The ensure the runs are representative of the samples, the coefficient of variation of the mean particle size in the number basis should be less than 5%. The same is recommended for combining samples to represent the emulsion. Particle size graphs should be shown as volume % versus particle size and utilize a smoothing technique by averaging up to 7 data points together to create a less cluttered graph. Finally, the analysis using RStudio identified moderate correlations between the viscosity test and the mean, d10, d50, d90, span and standard deviation of -0.548, -0.565, -0.543, -0.574, 0.427, and -0.474 respectively. These correlations along with guidelines from a particle size analyzer manufacturer led to the recommendation of reporting the mean, d50, and span, in the volume basis, as final results to describe a particle size distribution. These recommendations and guidelines serve as a steppingstone to further research about the best practices of conducting particle size analyses on asphalt emulsions. The results should be validated and refined with a formal experimental matrix