Search results for "lattice [space-time]"
showing 10 items of 692 documents
B-K-parameter from N-f=2 twisted mass lattice QCD
2011
We present an unquenched N-f = 2 lattice computation of the B-K parameter which controls K-0 - (K) over bar (0) oscillations. A partially quenched setup is employed with two maximally twisted dynamical (sea) light Wilson quarks, and valence quarks of both the maximally twisted and the Osterwalder-Seiler variety. Suitable combinations of these two kinds of valence quarks lead to a lattice definition of the B-K parameter which is both multiplicatively renormalizable and O(a) improved. Employing the nonperturbative RI-MOM scheme, in the continuum limit and at the physical value of the pion mass we get B-K(RGI) = 0.729 +/- 0.030, a number well in line with the existing quenched and unquenched d…
Representation of Autonomous Automata
2001
An autonomous automaton is a finite automaton with output in which the input alphabet has cardinality one when special reduced. We define the transition from automata to semigroups via a representation successful if given two incomparable automata (neither simulate the other), the semigroups representing the automata are distinct. We show that representation by the transition semigroup is not successful. We then consider a representation of automata by semigroups of partial transformations. We show that in general transition from automata to semigroups by this representation is not successful either. In fact, the only successful transition presented is the transiton to this semigroup of par…
Eu3+ ion distribution in oxyfluoride glass nanocomposites
2019
The authors are grateful to Dr. Andris Fedotovs for photography of the samples. This research is funded by the Latvian Council of Science, project “Novel transparent nanocomposite oxyfluoride materials for optical applications”, project No. LZP-2018/1-0335.
Search for the H-Dibaryon in two flavor Lattice QCD
2016
Parikshit Junnarkar∗, Anthony Francis, Jeremy Green, Chuan Miao, Thomas Rae, Hartmut Wittig Helmholtz-Institut Mainz, Institut fur Kernphysik, and PRISMA Cluster of Excellence, Johannes Gutenberg-Universitat Mainz, Germany Department of Physics and Astronomy, York University, Toronto Canada Bergische Universitat Wuppertal, Germany E-mail: junnarka@kph.uni-mainz.de, afranc@yorku.ca, green@kph.uni-mainz.de, chuan@kph.uni-mainz.de, thrae@uni-wuppertal.de, wittig@kph.uni-mainz.de
Opale: Photonische Kristalle
2007
Opale sind selbstorganisierte, kubisch dichtest gepackte Kolloidkristalle mit Kolloid-Durchmessern im Nanometer- und Submikrometerbereich. Aufgrund der periodisch modulierten Dielektrizitatskonstante bilden sich photonische Bandlucken aus, so dass die Ausbreitung von Licht mit Wellenlangen in der Grosenordnung der Gitterkonstanten unterdruckt wird. Dies erklart u.a. den brillianten Farbeindruck. Opale konnen synthetisch aus Polymer- oder Metalloxidkolloiden in einem Bottom-up-Prozess hergestellt und auf vielfaltige Weise chemisch funktionalisiert, strukturiert oder als Template fur ihre invertierten Strukturen verwendet werden. Anwendungsgebiete reichen von optischen Chips, Farbdisplays und…
Änderungen der Gitterstruktur hochpolymerer Einkristalle durch Bestrahlung im Elektronenmikroskop
1965
Die durch Bestrahlung mit Elektronen von 40 bis 80 kV hervorgerufenen Anderungen der Gitterstruktur von Polyathylen(PA)- und Polyoxymethylen(POM)-Einkristallen wurden unterrsucht. Dazu wurden Lage, Intensitat und Linienbreite der Reflexe im Elektronenbeugungsdiagramm in Abhangigkeit von der Bestrahlungsdosis gemessen. Vergleichende Untersuchungen wurden an einem Paraffin (C28H58) durchgefuhrt. Aus den Anderungen der Linienbreite konnte geschlossen werden, das im Falle des PA durch die Vernetzung zwischen benachbarten Ketten Gitterstorungen II. Art (parakristalline Storungen) hervorgerufen werden. Sie fuhren auch zu einer betrachtlichen Aufewitung des Gitters. Im Falle des Paraffins dagegen …
DFT study of a singleF center in cubic SrTiO3 perovskite
2006
Various properties of a cubic phase of SrTiO3 perovskite containing single F centers (neutral oxygen vacancies), including energies of their formation and migration, were simulated using different formalisms of density functional theory (DFT) as implemented into CRYSTAL-2003 and VASP computer codes. The lattice relaxation around the F center was found to be sensitive to both shape and size of supercells used. The larger the supercell, the closer the defect energy level in the bandgap lies to the conduction band bottom. It approaches the optical ionization energy of 0.49 eV for 270- and 320-atom supercells, where the distance between neighboring defects increases up to four lattice constants…
Dynamics of BF 4 - anion reorientation in the spin-crossover compound [Fe(1-n-propyl-1H-tetrazole) 6 ](BF 4 ) 2 and in its Zn II analogue
1999
19 F and 11 B spin-lattice relaxation times were measured in [ Zn ( ptz ) 6 ] ( BF 4 ) 2 and in the spin-crossover compound [ Fe ( ptz ) 6 ] ( BF 4 ) 2 . For both compounds BF 4 - anion reorientation is active above 50 K. For [ Zn ( ptz ) 6 ] ( BF 4 ) 2 , the anion-reorientation dynamics is different in the temperature regions of 50-90 K, 90-120 K, and above 150 K; between 120 and 150 K it changes rapidly reflecting a structural change. In [ Fe ( ptz ) 6 ] ( BF 4 ) 2 the mechanism for the paramagnetic relaxation involving the 19 F nuclei is found to be of the diffusion-limited type according to the theory of Lowe and Tse. The present results prove that the spin-crossover takes place in a dy…
Synthesis, crystal structure, optical, thermal and magnetic studies of a new organic-inorganic hybrid based on tetrachloroferrate (III)
2021
Abstract A new organic metal halide hybrid, benzyltrimethylammonium tetrachloroferrate (III), 1, ((BzMe3N)FeCl4) was synthesized by slow evaporation. The single crystal X-ray diffraction reveals that 1, crystallizes in the P-1 triclinic space group with the parameters a = 7.158 (5), b = 8.814 (8), c = 12.922 (4) A, α = 82.44 (5), β = 86.14 (4), γ = 87.13 (7)°, V = 805.7 (10) A3 and Z = 2. The structure packing exhibits a cationic and anionic layers alternation linked by means of C─H⋯Cl hydrogen interactions. The Hirshfeld surface and the lattice energy of 1 were calculated. The material purity was verified using X-ray powder diffraction and Rietveld refinements. The TG-DTA a…
Atomic scale DFT simulations of point defects in uranium nitride
2007
Atomic scale density functional calculations are used to predict the behaviour of defects in uranium mononitride (UN). Two different density functional codes (VASP and CASTEP) were employed with supercells containing from 8 to 250 atoms (providing a significant range of defect concentrations). Schottky and nitrogen Frenkel point defect formation energies, local lattice relaxations and overall lattice parameter change, as well as the defect induced electronic density redistribution, are discussed.