9,639 research outputs found
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 ). 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 . The -dependence of the resulting resistivity , 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 ,
and to cross over smoothly to the Fermi liquid form in the low-temperature limit. The underlying
approach, while naturally approximate, is moreover applicable to a broad range
of quantum impurity and related models
Communications network design and costing model programmers manual
Otpimization algorithms and techniques used in the communications network design and costing model for least cost route and least cost network problems are examined from the programmer's point of view. All system program modules, the data structures within the model, and the files which make up the data base are described
Communications network design and costing model technical manual
This computer model provides the capability for analyzing long-haul trunking networks comprising a set of user-defined cities, traffic conditions, and tariff rates. Networks may consist of all terrestrial connectivity, all satellite connectivity, or a combination of terrestrial and satellite connectivity. Network solutions provide the least-cost routes between all cities, the least-cost network routing configuration, and terrestrial and satellite service cost totals. The CNDC model allows analyses involving three specific FCC-approved tariffs, which are uniquely structured and representative of most existing service connectivity and pricing philosophies. User-defined tariffs that can be variations of these three tariffs are accepted as input to the model and allow considerable flexibility in network problem specification. The resulting model extends the domain of network analysis from traditional fixed link cost (distance-sensitive) problems to more complex problems involving combinations of distance and traffic-sensitive tariffs
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