82,025 research outputs found
Numerical iterative methods for Markovian dependability and performability models: new results and a comparison
In this paper we deal with iterative numerical methods to solve linear systems arising in continuous-time Markov chain (CTMC) models. We develop an algorithm to dynamically tune the relaxation parameter of the successive over-relaxation method. We give a sufficient condition for the Gauss-Seidel method to converge when computing the steady-state probability vector of a finite irreducible CTMC, an a suffient condition for the Generalized Minimal Residual
projection method not to converge to the trivial solution 0 when computing that vector. Finally, we compare several splitting-based iterative methods an a variant of the Generalized Minimal Residual projection method.Postprint (published version
Generalized Forward-Backward Splitting
This paper introduces the generalized forward-backward splitting algorithm
for minimizing convex functions of the form , where
has a Lipschitz-continuous gradient and the 's are simple in the sense
that their Moreau proximity operators are easy to compute. While the
forward-backward algorithm cannot deal with more than non-smooth
function, our method generalizes it to the case of arbitrary . Our method
makes an explicit use of the regularity of in the forward step, and the
proximity operators of the 's are applied in parallel in the backward
step. This allows the generalized forward backward to efficiently address an
important class of convex problems. We prove its convergence in infinite
dimension, and its robustness to errors on the computation of the proximity
operators and of the gradient of . Examples on inverse problems in imaging
demonstrate the advantage of the proposed methods in comparison to other
splitting algorithms.Comment: 24 pages, 4 figure
The Grover algorithm with large nuclear spins in semiconductors
We show a possible way to implement the Grover algorithm in large nuclear
spins 1/2<I<9/2 in semiconductors. The Grover sequence is performed by means of
multiphoton transitions that distribute the spin amplitude between the nuclear
spin states. They are distinguishable due to the quadrupolar splitting, which
makes the nuclear spin levels non-equidistant. We introduce a generalized
rotating frame for an effective Hamiltonian that governs the non-perturbative
time evolution of the nuclear spin states for arbitrary spin lengths I. The
larger the quadrupolar splitting, the better the agreement between our
approximative method using the generalized rotating frame and exact numerical
calculations.Comment: 11 pages, 18 EPS figures, REVTe
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