1,900 research outputs found
Nuclear Structure in the Framework of the Unitary Correlation Operator Method
Correlations play a crucial role in the nuclear many-body problem. We give an
overview of recent developments in nuclear structure theory aiming at the
description of these interaction-induced correlations by unitary
transformations. We focus on the Unitary Correlation Operator Method (UCOM),
which offers a very intuitive, universal and robust approach for the treatment
of short-range correlations. We discuss the UCOM formalism in detail and
highlight the connections to other methods for the description of short-range
correlations and the construction of effective interactions. In particular, we
juxtapose UCOM with the Similarity Renormalization Group (SRG) approach, which
implements the unitary transformation of the Hamiltonian through a very
flexible flow-equation formulation. The UCOM- and SRG-transformed interactions
are compared on the level of matrix elements and in many-body calculations
within the no-core shell model and with Hartree-Fock plus perturbation theory
for a variety of nuclei and observables. These calculations provide a detailed
picture of the similarities and differences as well as the advantages and
limitations of unitary transformation methods.Comment: 72 pages, 31 figure
Nuclear Structure - "ab initio"
An ab-initio description of atomic nuclei that solves the nuclear many-body
problem for realistic nuclear forces is expected to possess a high degree of
predictive power. In this contribution we treat the main obstacle, namely the
short-ranged repulsive and tensor correlations induced by the realistic
nucleon-nucleon interaction, by means of a unitary correlation operator. This
correlator applied to uncorrelated many-body states imprints short-ranged
correlations that cannot be described by product states. When applied to an
observable it induces the correlations into the operator, creating for example
a correlated Hamiltonian suited for Slater determinants. Adding to the
correlated realistic interaction a correction for three-body effects,
consisting of a momentum-dependent central and spin-orbit two-body potential we
obtain an effective interaction that is successfully used for all nuclei up to
mass 60. Various results are shown.Comment: 9 pages, Invited talk and poster at the international symposium "A
New Era of Nuclear Structure Physics" (NENS03), Niigata, Japan, Nov. 19-22,
200
Influence of polarizability on metal oxide properties studied by molecular dynamics simulations
We have studied the dependence of metal oxide properties in molecular
dynamics (MD) simulations on the polarizability of oxygen ions. We present
studies of both liquid and crystalline structures of silica (SiO2), magnesia
(MgO) and alumina (Al2O3). For each of the three oxides, two separately
optimized sets of force fields were used: (i) Long-range Coulomb interactions
between oxide and metal ions combined with a short-range pair potential. (ii)
Extension of force field (i) by adding polarizability to the oxygen ions. We
show that while an effective potential of type (i) without polarizable oxygen
ions can describe radial distributions and lattice constants reasonably well,
potentials of type (ii) are required to obtain correct values for bond angles
and the equation of state. The importance of polarizability for metal oxide
properties decreases with increasing temperature.Comment: 8 pages, 7 figure
Immigració i escola: experiències d’integració a Hamburg
L’article tracta, en primer lloc, el sistema escolar a l’Estat Federal d’Hamburg (República Federal d’Alemanya) i les mesures adoptades per a la integració de l’alumnat immigrant. Tot seguit, s’explica fil per randa l’experiència de l’escola Wielandstraße i la seva organització de classes de transició al sistema escolar regular. Es detallen els procediments per aconseguir el màxim èxit en els processos d’integració i es fa una valoració crítica de l’experiència. Finalment es fa una anàlisi i es presenten propostes de la didàctica de la d’educació física des d’una perspectiva intercultural
Sedex - eine praxistaugliche Methodik zur Beurteilung der Feststofflieferung in Wildbächen. SEDEX - A practical tool to estimate sediment deliveries in mountain torrents
Inmigración y escuela: experiencias de integración en Hamburgo
El artículo trata, en primer lugar, el sistema escolar en el Estado Federal de Hamburgo (República Federal de Alemania) y las medidas adoptadas para la integración del alumnado inmigrante. A continuación, se explica en detalle la experiencia de la escuela Wielandstraße y su organización de clases de transición al sistema escolar regular. Se detallan los procedimientos para lograr el máximo éxito en los procesos de integración y se hace una valoración crítica de la experiencia. Por último, se analiza y se presentan propuestas de la didáctica de la de Educación Física desde una perspectiva intercultural
The Swedish Sámi Parliament: A challenged recognition?
Work Package 4: National Case Studies of Challenges to Tolerance in Political LifeThe ACCEPT PLURALISM project (2010-2013) is funded by the European Commission under the Seventh Framework Programme, Socio-economic Sciences and Humanities. (Call FP7-SSH-2009-A, Grant Agreement no: 243837). Coordinator: Prof. Anna Triandafyllidou, Robert Schuman Centre for Advanced Studies, European University Institute
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