532 research outputs found
Chiral Symmetry Restoration in the Schwinger Model with Domain Wall Fermions
Domain Wall Fermions utilize an extra space time dimension to provide a
method for restoring the regularization induced chiral symmetry breaking in
lattice vector gauge theories even at finite lattice spacing. The breaking is
restored at an exponential rate as the size of the extra dimension increases.
Before this method can be used in dynamical simulations of lattice QCD, the
dependence of the restoration rate to the other parameters of the theory and,
in particular, the lattice spacing must be investigated. In this paper such an
investigation is carried out in the context of the two flavor lattice Schwinger
model.Comment: LaTeX, 37 pages including 18 figures. Added comments regarding power
law fitting in sect 7. Also, few changes were made to elucidate the content
in sect. 5.1 and 5.3. To appear in Phys. Rev.
Li-doped ZnO nanorods with single-crystal quality - non-classical crystallization and self-assembly into mesoporous materials
Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.The benefits and promise of nanoscale dimensions for the properties of (ceramic) semiconductors are widely known. 1-D nanostructures in particular have proven to be of extraordinary relevance due to their applicability in future electronic and optoelectronic devices. Key to successful technological implementation of semiconductor nanostructures is the control of their electronic properties via doping. Despite its tremendous importance, precise chemical doping of defined nano-objects has been addressed rarely so far. Frequent problems are the creation of secondary defects and related undesired property changes by incorporation of hetero-elements, and the difficulty in ensuring a uniform and precise positioning of the dopant in the nanocrystal lattice. Here, we present the synthesis of Li-doped zinc oxide nanorods, which possess excellent (single-crystal) quality. The method is based on a novel non-classical crystallization mechanism, comprising an unusually oriented disassembly step. Afterwards, the nanorods are incorporated into mesoporous layers using colloidal self-assembly. Proof-of-principle gas sensing measurements with these novel materials demonstrate the beneficial role of Li-doping, indicating not only better conductivity but also the occurrence of catalytic effects
Perfect Lattice Actions for Staggered Fermions
We construct a perfect lattice action for staggered fermions by blocking from
the continuum. The locality, spectrum and pressure of such perfect staggered
fermions are discussed. We also derive a consistent fixed point action for free
gauge fields and discuss its locality as well as the resulting static
quark-antiquark potential. This provides a basis for the construction of
(classically) perfect lattice actions for QCD using staggered fermions.Comment: 30 pages, LaTex, 10 figure
Exact solution (by algebraic methods) of the lattice Schwinger model in the strong-coupling regime
Using the monomer--dimer representation of the lattice Schwinger model, with
Wilson fermions in the strong--coupling regime (), we
evaluate its partition function, , exactly on finite lattices. By studying
the zeroes of in the complex plane for a large number of
small lattices, we find the zeroes closest to the real axis for infinite
stripes in temporal direction and spatial extent and 3. We find evidence
for the existence of a critical value for the hopping parameter in the
thermodynamic limit on the real axis at about . By looking at the behaviour of quantities, such as the chiral
condensate, the chiral susceptibility and the third derivative of with
respect to , close to the critical point , we find some indications
for a continuous phase transition.Comment: 22 pages (6 figures
Alternative shear reinforcement for reinforced concrete flat slabs
This paper presents the first series of validation tests for a patented shear reinforcement system for reinforced concrete flat slabs. The system, called “Shearband,” consists of elongated thin steel strips punched with holes, which undulate into the slab from the top surface. The main advantages of the new reinforcement system are structural effectiveness, flexibility, simplicity, and speed of construction. Four reinforced concrete slabs were tested in a specially designed test rig. The slabs reinforced in shear exhibited ductile behavior after achieving their full flexural potential, thus proving the effectiveness of the new reinforcement. This paper reviews briefly existing types of shear reinforcement and identifies the need for more efficient and economic solutions. Details of the experimental setup and results are given, including strain and deflection measurements as well as photographs of sections through the slabs. Finally, comparisons are made with the ACI 318 and BS8110 code predictions, which confirm that the system enabled the slabs to avoid punching shear failure and achieve their flexural potential. In addition, both codes are shown to lead to conservative estimates of flexural and punching shear capacities of reinforced concrete slabs
Staggered versus overlap fermions: a study in the Schwinger model with
We study the scalar condensate and the topological susceptibility for a
continuous range of quark masses in the Schwinger model with
dynamical flavors, using both the overlap and the staggered discretization. At
finite lattice spacing the differences between the two formulations become
rather dramatic near the chiral limit, but they get severely reduced, at the
coupling considered, after a few smearing steps.Comment: 15 pages, 7 figures, v2: 1 ref corrected, minor change
Hinführung und Rahmenbedingungen für die Entwicklung eines toolbasierten Beratungsansatzes für Seamless Learning Konzeptionen
Wie gestalte ich Seamless Learning Konzepte? Mit der Entwicklung eines toolbasierten Beratungsansatzes wurden die Materialien, Entwicklungsschritte und theoretischen Konzepte zu Seamless Learning aus den Erfahrungen des IBH-Lab Seamless Learning Basisprojekts aufbereitet und in ein Unterstützungssystem für Dozierende übersetzt. Der Beitrag beschreibt den Ansatz und die Funktionsweise des Beratungsansatzes, thematisiert die erkannten Probleme bei der Entwicklung und die technologischen Grundlagen. Im Mittelpunkt steht die Beschreibung der entwickelten Seamless Learning Plattform und die verschiedenen Unterstützungsfunktionen, die die Seamless Learning Plattform bietet. Verschiedene Nutzungsszenarien, ein Ausblick auf weitere Nutzungsformen sowie eine erste kritische Diskussion runden die Darstellung ab. Mit dem Beitrag steht den Leserinnen und Lesern eine strukturierte Einführung in den entwickelten toolbasierten Beratungsansatz zum Seamless Learning zur Verfügung
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