Quasiparticle Self-Consistent GW Theory

In past decades the scientific community has been looking for a reliable first-principles method to predict the electronic structure of solids with high accuracy. Here we present an approach which we call the quasiparticle self-consistent GW approximation (QpscGW). It is based on a kind of self-consistent perturbation theory, where the self-consistency is constructed to minimize the perturbation. We apply it to selections from different classes of materials, including alkali metals, semiconductors, wide band gap insulators, transition metals, transition metal oxides, magnetic insulators, and rare earth compounds. Apart some mild exceptions, the properties are very well described, particularly in weakly correlated cases. Self-consistency dramatically improves agreement with experiment, and is sometimes essential. Discrepancies with experiment are systematic, and can be explained in terms of approximations made.Comment: 12 pages, 3 figure

Deformable self-propelled particles

A theory of self-propelled particles is developed in two dimensions assuming that the particles can be deformed from a circular shape when the propagating velocity is increased. A coupled set of equations in terms of the velocity and a tensor variable to represent the deformation is introduced to show that there is a bifurcation from a straight motion to a circular motion of a single particle. Dynamics of assembly of the particles is studied numerically where there is a global interaction such that the particles tend to cause an orientational order.Comment: 4pages, 4figure

Adequacy of Approximations in GW Theory

We use an all-electron implementation of the GW approximation to analyze several possible sources of error in the theory and its implementation. Among these are convergence in the polarization and Green's functions, the dependence of QP levels on choice of basis sets, and differing approximations for dealing with core levels. In all GW calculations presented here, G and W are generated from the local-density approximation (LDA), which we denote as the \GLDA\WLDA approximation. To test its range of validity, the \GLDA\WLDA approximation is applied to a variety of materials systems. We show that for simple sp semiconductors, \GLDA\WLDA always underestimates bandgaps; however, better agreement with experiment is obtained when the self-energy is not renormalized, and we propose a justification for it. Some calculations for Si are compared to pseudopotential-based \GLDA\WLDA calculations, and some aspects of the suitability of pseudopotentials for GW calculations are discussed.Comment: 38 pages,6 figures. Minor Revision

Spin wave dispersion based on the quasiparticle self-consistent GWGW method: NiO, MnO and α\alpha-MnAs

We present spin wave dispersions in MnO, NiO, and $\alpha$-MnAs based on the quasiparticle self-consistent $GW$ method (\qsgw), which determines an optimum quasiparticle picture. For MnO and NiO, \qsgw results are in rather good agreement with experiments, in contrast to the LDA and LDA+U description. For $\alpha$-MnAs, we find a collinear ferromagnetic ground state in \qsgw, while this phase is unstable in the LDA.Comment: V2: add another figure for SW life time. Formalism is detaile

The Fermi surface of CeCoIn5: dHvA

Measurements of the de Haas - van Alphen effect in the normal state of the heavy Fermion superconductor CeCoIn5 have been carried out using a torque cantilever at temperatures ranging from 20 to 500 mK and in fields up to 18 tesla. Angular dependent measurements of the extremal Fermi surface areas reveal a more extreme two dimensional sheet than is found in either CeRhIn5 or CeIrIn5. The effective masses of the measured frequencies range from 9 to 20 m*/m0.Comment: 4 pages, 2 figures, submitted to PRB Rapid

Alternative formalism to the slave particle mean field theory of the t-J model without deconfinement

An alternative formalism that does not require the assumption of the deconfinement phase of a U(1) gauge field is proposed for the slave particle mean field theory. Starting form the spin-fermion model, a spinon field, which is either fermion or boson, is introduced to represent the localized spin moment. We find a d-wave superconductive state in the mean field theory in the case of the fermion representation of the localized spin moment that corresponds to the slave boson mean field theory of the t-J model, whereas the d-wave superconductive state is absent in case of the Schwinger boson representation of the localized spin moments.Comment: 8 page

Availability, attitudes and costs of selected dental services in a low-income country

ABSTRACT The aim of this study was to determine the availability of selected dental services, attitudes towards such services and economic factors associated with their utilization in a low-income country. Data utilized for this study was collected in two phases. Phase I was a survey of all dental facilities in four selected regions in Tanzania. The survey was administered to officers-in-charge of dental facilities and other dental practitioners working within these facilities. Phase II was a series of cross-sectional studies conducted among outpatients attending four selected regional hospitals in Tanzania. Data was collected using self-administered questionnaires. Dental materials and equipment were inconsistently available and only 3/28 studied dental facilities had all the seven investigated equipment fully functional and in use. The self-rated competency among dental practitioners ranged from 6.4 to 9.8 for all six procedures questioned, but equal scores between cadres were only for tooth extractions (9.7 vs. 9.1 respectively). Competencies for placing restorations were all rated lower by other cadres (p varied from <. 05 to < .001). Most of the patients had a negative overall attitude (-1.99) towards tooth filling treatment although those with previous tooth filling experience had positive attitudes (1.00). The mean willingness-to-pay (WTP) values for tooth filling (7,398 and 7,726 Tshs for anterior and posterior teeth, respectively) were higher (p < 0.001) than for tooth extraction irrespective of tooth type (5,448 and 6,188 Tshs, respectively). Being 45+ years increased the likelihood to offer lower WTP values. More than half (55%) of the patients would experience significant financial impacts as a result of their utilization of dental services. The findings clearly suggest that there are a multitude of factors that influence the observed dental treatment patterns being predominated by tooth extractions in Tanzania. Keywords: Willingness-to-pay, costs, dental services, attitudes, TanzaniaTIIVISTELMÄ Valikoitujen hammashoitopalvelujen saatavuus, niihin liittyvät asenteet ja käytön kustannukset vähävaraisessa maassa Tutkimus selvitti valikoitujen hammashoitopalveluiden saatavuutta sekä niihin liittyviä asenteita ja käyttöön liittyviä taloudellisia tekijöitä vähävaraisessa maassa. Ensin tehtiin kyselytutkimus kaikissa hammashoitopalveluja tarjoavissa yksiköissä neljällä valitulla tansanialaisella hallintoalueella näiden yksiköiden johtajien ja hammashoitoa antavien työntekijöiden keskuudessa. Toiseksi toteutettiin sarja poikkileikkaustutkimuksia kyselyin näiden neljän hallintoalueen avohoitopotilaiden keskuudessa. Kyselyissä selvitettiin valikoitujen hammashoitopalvelujen kustannuksia, hammashoitomateriaalien ja -laitteiden saatavuutta, hammashoidon työntekijöiden kokemia valmiuksia, potilaiden asenteita ja maksuhalukkuutta paikkaushoitoon sekä potilaille hammashoidosta aiheutuviin kustannuksia. Materiaaleja ja laitteita oli vaihtelevasti saatavilla. Vain kolmessa tutkitusta 28 hoitolasta kaikki seitsemän tutkimuksessa tarkasteltua laitetta olivat käytössä ja toimintakunnossa. Hammaslääkärien kokemat valmiudet toimenpiteisiin vaihtelivat (6,4–9,8) ja olivat saman tasoisia muiden ammattiryhmien kanssa vain poistoissa (9,7 vs. 9,1). Paikkausvalmiudet olivat alempia muilla ammattiryhmillä (p <0,05–<0,001). Useimmilla potilailla oli negatiivinen kokonaisasenne (-1,99) paikkaushoitoon. Heillä, joilla oli aiempaa kokemusta paikkaushoidosta, oli positiivinen asenne (1,00). Paikkaushoidon maksuhalukkuuden keskiarvot olivat huomattavasti korkeammat (7398 Tansanian shillinkiä (Tshs) etualueella ja 7726 Tshs taka-alueella) kuin hammaspoistojen maksuhalukkuuden (5448 Tshs etualueella ja 6188 Tshs taka-alueella, p<0,001). Hammashoitopalvelujen käyttö aiheutti yli puolelle (55 %) tutkituista potilaista merkittäviä taloudellisia vaikutuksia. Tulokset osoittavat selvästi, että Tansaniassa monet tekijät vaikuttavat hammashoitopalvelujen tuotantoon, jota hallitsevat hampaiden poistot. Avainsanat: Maksuhalukkuus, kustannukset, hammashoitopalvelut, asenteet, Tansani

The sixth Painleve equation arising from D_4^{(1)} hierarchy

The sixth Painleve equation arises from a Drinfel'd-Sokolov hierarchy associated with the affine Lie algebra of type D_4 by similarity reduction.Comment: 14 page

Notes on Matter in Horava-Lifshitz Gravity

We investigate the dynamics of a scalar field governed by the Lifshitz-type action which should appear naturally in Horava-Lifshitz gravity. The wave of the scalar field may propagate with any speed without an upper bound. To preserve the causality, the action cannot have a generic form. Due to the superluminal propagation, a formation of a singularity may cause the breakdown of the predictability of the theory. To check whether such a catastrophe could occur in Horava-Lifshitz gravity, we investigate the dynamics of a dust. It turns out that the dust does not collapse completely to form a singularity in a generic situation, but expands again after it attains a maximum energy density.Comment: 14 pages, references adde