Phase diagram and dynamic response functions of the Holstein-Hubbard model

We present the phase diagram and dynamical correlation functions for the Holstein-Hubbard model at half filling and at zero temperature. The calculations are based on the Dynamical Mean Field Theory. The effective impurity model is solved using Exact Diagonalization and the Numerical Renormalization Group. Excluding long-range order, we find three different paramagnetic phases, metallic, bipolaronic and Mott insulating, depending on the Hubbard interaction U and the electron-phonon coupling g. We present the behaviour of the one-electron spectral functions and phonon spectra close to the metal insulator transitions.Comment: contribution to the SCES04 conferenc

Single particle spectrum of the flux phase in the FM Kondo Model

We investigate the 2D ferromagnetic Kondo lattice model for manganites with classical corespins at Hund's rule coupling J_H=6, with antiferromagnetic superexchange 0.03 < J' < 0.05. We employ canonical and grand canonical unbiased Monte Carlo simulations and find paramagnetism, weak ferromagnetism and the Flux phase, depending on doping and on J'. The observed single particle spectrum in the flux phase differs from the idealized infinite lattice case, but agrees well with an idealized finite lattice case with thermal fluctuations.Comment: contribution to the SCES04 conferenc

Outsourcing and Employment: A Decomposition Approach

In this paper we study the employment effects of changes in the levels and patterns of outsourcing in the Austrian economy over the periods 1995-2000 and 2000-2003. Based on an input-output framework we apply a hierarchical decomposition analysis to disentangle the employment effects of changes in labour productivity, technical input coefficients and final demand components. Outsourcing is modelled as changes in the shares of domestically produced intermediates. For this some further details can be derived by distinguishing between intermediate imports of energy, material and service products or according to educational intensities of the imported intermediate products. Following this approach first allows to study the direct and indirect effects of changes in the levels and structures of outsourcing.Second, the framework takes account of all 60 sectors (products) of the economy and thus also includes employment effects of service offshoring. Third, we also calculate the employment effects for three employment groups distinguished by educational attainment levels. This paper thus provides a comprehensive picture of employment effects of outsourcing in the Austrian economy.Foreign Direct Investment, outsourcing, offshoring, employment effects, hierarchical decomposition, input-output modelling

Automatic Classification of Text Databases through Query Probing

Many text databases on the web are "hidden" behind search interfaces, and their documents are only accessible through querying. Search engines typically ignore the contents of such search-only databases. Recently, Yahoo-like directories have started to manually organize these databases into categories that users can browse to find these valuable resources. We propose a novel strategy to automate the classification of search-only text databases. Our technique starts by training a rule-based document classifier, and then uses the classifier's rules to generate probing queries. The queries are sent to the text databases, which are then classified based on the number of matches that they produce for each query. We report some initial exploratory experiments that show that our approach is promising to automatically characterize the contents of text databases accessible on the web.Comment: 7 pages, 1 figur

Outsourcing in cattle ectoparasite control - a promising opportunity.

Records of the occurrence of resistant populations of cattle parasites are becoming increasingly frequent in different regions of the country. These reports refer in general to the horn fly, Haematobia irritans.Edição dos trabalhos do:7th International conference on urban pests. Updates on urban pest control. Ouro Preto, 2011

Adult Female Spruce Bedworm, \u3ci\u3eChoristoneura Fumiferana\u3c/i\u3e (Lepidoptera: Tortricidae), Dry Weight in Relationship to Pupal Fresh Weight and Case Diameter

(excerpt) The weights of adult insects are often measured in production and population studies in order to estimate such variables as growth rates, food conversion efficiencies, fecundity, and others. For the eastern spruce budworm, Choristoneura fumiferana (Clemens), both pupal fresh weights and pupal case diameters have been measured as indicators of adult fecundity and adult dry weights (Miller 1957). However, there are no reports explicitly showing the relationship between these metric pupal variables and adult dry weights. This is the goal of this note

First- and Second Order Phase Transitions in the Holstein-Hubbard Model

We investigate metal-insulator transitions in the Holstein-Hubbard model as a function of the on-site electron-electron interaction U and the electron-phonon coupling g. We use several different numerical methods to calculate the phase diagram, the results of which are in excellent agreement. When the electron-electron interaction U is dominant the transition is to a Mott-insulator; when the electron-phonon interaction dominates, the transition is to a localised bipolaronic state. In the former case, the transition is always found to be second order. This is in contrast to the transition to the bipolaronic state, which is clearly first order for larger values of U. We also present results for the quasiparticle weight and the double-occupancy as function of U and g.Comment: 6 pages, 5 figure

Phase diagram for the one-dimensional Hubbard-Holstein model: A density-matrix renormalization group study

Phase diagram of the Hubbard-Holstein model in the coexistence of electron-electron and electron-phonon interactions has been theoretically obtained with the density-matrix renormalization group method for one-dimensional (1D) systems, where an improved warm-up (the recursive sweep) procedure has enabled us to calculate various correlation functions. We have examined the cases of (i) the systems half-filled by electrons for the full parameter space spanned by the electron-electron and electron-phonon coupling constants and the phonon frequency, (ii) non-half-filled system, and (iii) trestle lattice. For (i), we have detected a region where both the charge and on-site pairing correlations decay with power-laws in real space, which suggests a metallic behavior. While pairing correlations are not dominant in (i), we have found that they become dominant as the system is doped in (ii), or as the electronic band structure is modified (with a broken electron-hole symmetry) in (iii) in certain parameter regions.Comment: 12 pages, 14 figures, submitted to Phys. Rev.

Impulsive traits and 5-HT2A receptor promoter polymorphism in alcohol dependents: Possible association but no influence of personality disorders

Objective: Impulsive behavior in alcoholics puts them at serious risk of severer course of disease and has been related to the serotonergic neurotransmission dysfunction. The aim of this study is to investigate the association between impulsive aggression in alcohol dependents with regard to the G-1438A polymorphism in the promoter region of the 5-HT2A receptor gene. Furthermore, we investigated the statistical interaction between 5-HT2A alleles, antisocial personality disorder (APD) and impulsive aggression in alcohol dependents. Alcohol dependents were investigated because these personality disorders and impulsive behavior are very frequent in alcohol dependence anf of clinical relevance. Methods: One hundred and thirty-five patients of German descent meeting DSM-IV criteria of alcohol dependence were recruited. Blood samples were taken from alcohol dependents to determine 5-HT2A promoter polymorphisms using PCR (polymerase chain reaction) of lymphocyte DNA. Impulsive aggression was assessed using a German version of the Barratt Impulsiveness Scale which was translated and backtranslated. Alcohol dependents were subdivided into low- or high-impulsivity groups using a median split of the Barratt score. APD and borderline personality disorder (BPD) were assessed using the SCID-II interview. Results: The low-impulsivity group was slightly older and showed a later age at alcoholism onset than the highly impulsive group. Alcohol dependents with high impulsive traits showed a significant association with 5-HT2A 1438 A alleles. After excluding alcohol dependents with APD or BPD from the analysis, this association remained significant. Furthermore, no association between APD, BPD and 5-HT2A alleles was noted. Conclusions: Inpatient alcohol dependents showed a significant association between 5-HT2A A alleles and impulsive traits, independent of the presence of APD or BPD. No association was noted between personality disorders and the polymorphism. This is the first report about an association of 5-HT2A promoter polymorphism and impulsive behavior in alcohol dependents. This finding may refer only to impulsive traits and may be independent of personality disorders in this sample. These results have to be confirmed in larger samples and in healthy control subjects to determine whether this association is of general validity. Copyright (C) 2001 S. Karger AG, Basel