131 research outputs found
ParIC : A Family of Parallel Incomplete Cholesky Preconditioners
A class of parallel incomplete factorization preconditionings
for the solution of large linear systems is investigated. The approach may
be regarded as a generalized domain decomposition method. Adjacent
subdomains have to communicate during the setting up of the precon
ditioner, and during the application of the preconditioner. Overlap is
not necessary to achieve high performance. Fillin levels are considered
in a global way. If necessary, the technique may be implemented as a
global reordering of the unknowns. Experimental results are reported
for twodimensional problems
SU(2) Yang-Mills Theory with extended Supersymmetry in a Background Magnetic Field
The vacuum structure of N=2 (and N=4) SUSY Yang-Mills theory is analyzed in
detail by considering the effective potential for constant background scalar-
magnetic fields within different approximations. We compare the one-loop
approximation with- or without instanton improved effective coupling with the
one-loop result in the dual desription. For N=2 we find that non-perturbative
monopole degrees of freedom remove the non-trivial minima present in the
(improved) one-loop potential in the strong-coupling regime. The combination of
Yang-Mills and dual desription leads to a self-consistent effective potential
over the full range of background fields.Comment: 15 pages, Revtex, 3 figures, References added, section two shortened,
some minor remarks and corrections adde
Four-dimensional anti-de Sitter black holes from a three-dimensional perspective: Full complexity
The dimensional reduction of black hole solutions in four-dimensional (4D)
general relativity is performed and new 3D black hole solutions are obtained.
Considering a 4D spacetime with one spacelike Killing vector, it is possible to
split the Einstein-Hilbert-Maxwell action with a cosmological term in terms of
3D quantities. Definitions of quasilocal mass and charges in 3D spacetimes are
reviewed. The analysis is then particularized to the toroidal charged rotating
anti-de Sitter black hole. The reinterpretation of the fields and charges in
terms of a three-dimensional point of view is given in each case, and the
causal structure analyzed.Comment: 26 pages, 1 figure, Uses revtex
On mutual impact of numerical linear algebra and large-scale optimization with focus on interior point methods
An Implementation of Tarjan's Algorithm for the Block Triangularization of a Matrix
An implementation of Tarj an's algorithm for symmetrically permuting a given matrix to block tmangular form is described. The discussion includes a flowchart of the algorithm, a com-plexity analysis, and a comparison with the earlier widely used algorithm of Sargent and Westerberg. T~ming results are presented from several experiments using the code developed by the authors
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