529,716 research outputs found
Application of the Exact Muffin-Tin Orbitals Theory: the Spherical Cell Approximation
We present a self-consistent electronic structure calculation method based on
the {\it Exact Muffin-Tin Orbitals} (EMTO) Theory developed by O. K. Andersen,
O. Jepsen and G. Krier (in {\it Lectures on Methods of Electronic Structure
Calculations}, Ed. by V. Kumar, O.K. Andersen, A. Mookerjee, Word Scientific,
1994 pp. 63-124) and O. K. Andersen, C. Arcangeli, R. W. Tank, T.
Saha-Dasgupta, G. Krier, O. Jepsen, and I. Dasgupta, (in {\it Mat. Res. Soc.
Symp. Proc.} {\bf 491}, 1998 pp. 3-34). The EMTO Theory can be considered as an
{\it improved screened} KKR (Korringa-Kohn-Rostoker) method which is able to
treat large overlapping potential spheres. Within the present implementation of
the EMTO Theory the one electron equations are solved exactly using the Green's
function formalism, and the Poisson's equation is solved within the {\it
Spherical Cell Approximation} (SCA). To demonstrate the accuracy of the
SCA-EMTO method test calculations have been carried out.Comment: 20 pages, 10 figure
Optical conductivity in A3C60 (A=K, Rb)
We study the optical conductivity in A3C60 (A =K, Rb). The effects of the
electron-phonon interaction is included to lowest order in the coupling
strength lambda. It is shown that this leads to a narrowing of the Drude peak
by a factor 1+lambda and a transfer of weight to a mid-infrared peak at
somewhat larger energies than the phonon energy. Although this goes in the
right direction, it is not sufficient to describe experiment.Comment: 5 pages, revtex, 2 figures more information at
http://librix.mpi-stuttgart.mpg.de/docs/ANDERSEN/fullerene
Pauli susceptibility of A3C60 (A=K, Rb)
The Pauli paramagnetic susceptibility of A3C60 (A= K, Rb) compounds is
calculated. A lattice quantum Monte Carlo method is applied to a multi-band
Hubbard model, including the on-site Coulomb interaction U. It is found that
the many-body enhancement of the susceptibility is of the order of a factor of
three. This reconciles estimates of the density of states from the
susceptibility with other estimates. The enhancement is an example of a
substantial many-body effect in the doped fullerenes.Comment: 4 pages, revtex, 2 figures, submitted to Phys. Rev. B more
information at http://www.mpi-stuttgart.mpg.de/dokumente/andersen/fullerene
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An inwardly rectifying K+ channel is required for patterning.
Mutations that disrupt function of the human inwardly rectifying potassium channel KIR2.1 are associated with the craniofacial and digital defects of Andersen-Tawil Syndrome, but the contribution of Kir channels to development is undefined. Deletion of mouse Kir2.1 also causes cleft palate and digital defects. These defects are strikingly similar to phenotypes that result from disrupted TGFβ/BMP signaling. We use Drosophila melanogaster to show that a Kir2.1 homolog, Irk2, affects development by disrupting BMP signaling. Phenotypes of irk2 deficient lines, a mutant irk2 allele, irk2 siRNA and expression of a dominant-negative Irk2 subunit (Irk2DN) all demonstrate that Irk2 function is necessary for development of the adult wing. Compromised Irk2 function causes wing-patterning defects similar to those found when signaling through a Drosophila BMP homolog, Decapentaplegic (Dpp), is disrupted. To determine whether Irk2 plays a role in the Dpp pathway, we generated flies in which both Irk2 and Dpp functions are reduced. Irk2DN phenotypes are enhanced by decreased Dpp signaling. In wild-type flies, Dpp signaling can be detected in stripes along the anterior/posterior boundary of the larval imaginal wing disc. Reducing function of Irk2 with siRNA, an irk2 deletion, or expression of Irk2DN reduces the Dpp signal in the wing disc. As Irk channels contribute to Dpp signaling in flies, a similar role for Kir2.1 in BMP signaling may explain the morphological defects of Andersen-Tawil Syndrome and the Kir2.1 knockout mouse
A Letter from the ATE-K President
A letter from the ATE-K President, Dr. Gary Andersen
On the Fourier transform of Schwartz functions on Riemannian Symmetric Spaces
Consider the (Helgason-) Fourier transform on a Riemannian symmetric space
G/K. We give a simple proof of the L^p-Schwartz space isomorphism theorem (0 <p
\le 2) for K-finite functions. The proof is a generalization of J.-Ph. Anker's
proof for K-invariant functions
Static triplet correlations in glass-forming liquids: A molecular dynamics study
We present a numerical evaluation of the three-point static correlations
functions of the Kob-Andersen Lennard-Jones binary mixture and of its purely
repulsive, Weeks-Chandler-Andersen variant. In the glassy regime, the two
models possess a similar pair structure, yet their dynamics differ markedly.
The static triplet correlation functions S^(3) indicate that the local ordering
is more pronounced in the Lennard-Jones model, an observation consistent with
its slower dynamics. A comparison of the direct triplet correlation functions
c^(3) reveals that these structural differences are due, to a good extent, to
an amplification of the small discrepancies observed at the pair level. We
demonstrate the existence of a broad, positive peak at small wave-vectors and
angles in c^(3). In this portion of k-space, slight, systematic differences
between the models are observed, revealing "genuine" three-body contributions
to the triplet structure. The possible role of the low-k features of c^(3) and
the implications of our results for dynamic theories of the glass transition
are discussed.Comment: 9 pages, 8 figures, contribution to the JCP Special Issue on the
Glass Transitio
Finding the K shortest hyperpaths using reoptimization
The shortest hyperpath problem is an extension of the classical shortest path problem and has applications in many different areas. Recently, algorithms for finding the K shortest hyperpaths in a directed hypergraph have been developed by Andersen, Nielsen and Pretolani. In this paper we improve the worst-case computational complexity of an algorithm for finding the K shortest hyperpaths in an acyclic hypergraph. This result is obtained by applying new reoptimization techniques for shortest hyperpaths. The algorithm turns out to be quite effective in practice and has already been successfully applied in the context of stochastic time-dependent networks, for finding the K best strategies and for solving bicriterion problems.Network programming; Directed hypergraphs; K shortest hyperpaths; K shortest paths
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