11 documentos corresponden a la consulta.
Palabras contadas: algebra: 69, matrix: 116
Bochicchio, R.C. - Rial, D.
J Chem Phys 2012;137(22)
2012
Descripción: A novel appropriate definition for the density matrix for an interacting Coulombic driven atomic or molecular system with non-integer number of particles is given. Our approach leads to a direct derivation of the proposal reported by Perdew [Phys. Rev. Lett. 49, 1691 (1982)]10.1103/PhysRevLett.49.1691 and points out its suitability and perspective advances. © 2012 American Institute of Physics.
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Milaszewicz, J.P.
Comput Math Appl 1995;30(1):79-90
1995
Temas: Discretized Newton method - Functional elimination - Nonlinear systems - Order convex functions - Approximation theory - Boundary value problems - Convergence of numerical methods - Differentiation (calculus) - Function evaluation - Iterative methods
Descripción: The improvement in convergence by means of accurate functional elimination in the context of the monotone Newton theorem is further analyzed and extended to discrete approximations of the Newton method. © 1995.
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Alcoba, D.R. - Lain, L. - Torre, A. - Bochicchio, R.C.
J Chem Phys 2005;123(14)
2005
Temas: Atomic domains - Density matrix - Electron system - Spatial decomposition - Atoms - Chemical bonds - Eigenvalues and eigenfunctions - Electrons - Matrix algebra - Molecules
Descripción: This work describes a simple spatial decomposition of the first-order reduced density matrix corresponding to an N -electron system into first-order density matrices, each of them associated to an atomic domain defined in the theory of atoms in molecules. A study of the representability of the density matrices arisen from this decomposition is reported and analyzed. An appropriate treatment of the eigenvectors of the matrices defined over atomic domains or over unions of these domains allows one to describe satisfactorily molecular properties and chemical bondings within a determined molecule and among its fragments. Numerical determinations, performed in selected molecules, confirm the reliability of our proposal. © 2005 American Institute of Physics.
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Bergero, P. - Peruani, F. - Solovey, G. - Irurzun, I.M. - Vicente, J.L. - Mola, E.E.
Phys. Rev. E Stat. Nonlinear Soft Matter Phys. 2004;69(1 2):161231-161236
2004
Temas: Dielectric materials - Electric breakdown - Electric conductors - Electric field effects - Electric insulators - Electrodes - Fractals - Interfaces (materials) - Matrix algebra - Particle size analysis
Descripción: The dielectric breakdown model to describe the dielectric breakdown patterns in both conductor-loaded and insulator-loaded composites was generalized. With a variable concentration p, particles were distributed at random in a matrix. According to particle characteristics, the generalized model assigned different probabilities to breakdown channel formation. The fractal dimension D and the parameters of the Weibull distribution was used to characterize the dielectric breakdown patterns.
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Bochicchio, R.C. - Torre, A. - Lain, L.
J Chem Phys 2005;122(8)
2005
Temas: Condensed matter - Cumulants - Molecular systems - Quantum fields - Computational methods - Correlation methods - Electrons - Functions - Mathematical models - Matrix algebra
Descripción: This paper describes a matrix formulation for the correlated hole theory within the framework of the domain-averaged model in many electron systems (atoms, molecules, condensed matter, etc.). General relationships between this quantity and one-particle reduced density matrices for any independent particle or correlated state functions are presented. This formulation turns out to be suitable for computational purposes due to the straightforward introduction of cumulants of two-particle reduced density matrices within the quantum field structure. Numerical calculations in selected simple molecular systems have been performed in order to determine preliminary correlated values for such a quantity.
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Cohen, D. - Wisniacki, D.A.
Phys. Rev. E Stat. Nonlinear Soft Matter Phys. 2003;67(2 2):262061-2620614
2003
Temas: Hamiltonians - Kinetic energy - Matrix algebra - Perturbation techniques - Energy distribution - Quantum theory
Descripción: The evolution of the energy distribution was studied for a stadium with moving balls. A one period driving cycle was considered, which was characterized by an amplitude A and a wall velocity V. The spreading mechanism was dominated by transitions between neighboring levels for an extremely slow wall velocity V, while for larger velocities, the spreading mechanism had both perturbative and nonperturbative features.
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Landoni, M. - Duschak, V.G. - Erra-Balsells, R. - Couto, A.S.
J. Am. Soc. Mass Spectrom. 2008;19(7):923-926
2008
Temas: Amides - Computer networks - Desorption - Lipids - Mass spectrometers - Mass spectrometry - Matrix algebra - Microfluidics - Network protocols - Pulsed laser deposition
Descripción: Each day, advances in the instrumentation and operating protocols bring new applications and insights into the molecular processes of ultra violet-matrix assisted laser desorption/ionization-mass spectrometry (UV-MALDI MS), increasing its potential use. We report here an approach in which mass spectrometry analysis of sphingolipids has been performed using a fluorescent tag (nitrobenz-2-oxa-1, 3-diazole, NBD) covalently linked to the sphingoid base as matrix. Thus, different labeled-sphingolipids were analyzed: ceramide, dihydroceramide, acetylceramide, glucosylceramide, galactosylceramide, galactosyldihydroceramide. In addition an extract of glycosphingolipids obtained from epimastigote forms of Trypanosoma cruzi metabolically labeled with NBD-ceramide was analyzed. The goal of this work is to show that no matrix needs to be added for the mass spectrometry analysis as the same tag used to label the lipids may generate efficiently analyte ions to obtain high quality signals. © 2008 American Society for Mass Spectrometry.
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Melo, J.I. - Ruiz de Azua, M.C. - Giribet, C.G. - Aucar, G.A. - Romero, R.H.
J Chem Phys 2003;118(2):471-486
2003
Temas: Approximation theory - Differential equations - Eigenvalues and eigenfunctions - Ground state - Hamiltonians - Magnetic shielding - Matrix algebra - State space methods - Tensors - Coulomb and Breit two-body interaction operators
Descripción: A two-component theory for shielding calculations starting from a four-component Rayleigh-Schrodinger perturbation theory (RSPT) formalism is presented. Thus, a set of operators entering the RSPT expressions in terms of the Schrodinger molecular spectrum are derived by expanding such four-component expression as a power series in c-1. All formal expressions are retained, without neglecting any terms in the intermediate steps of the derivation.
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De Leo, M. - Dratman, E. - Matera, G.
J. Complexity 2005;21(4):502-531
2005
Temas: Complexity - Conditioning - Homotopy algorithms - Polynomial system solving - Semi-linear parabolic problems - Stationary solutions - Algorithms - Boundary value problems - Mathematical models - Matrix algebra
Descripción: We consider a family of polynomial systems which arises in the analysis of the stationary solutions of a standard discretization of certain semi-linear second-order parabolic partial differential equations. We prove that this family is well-conditioned from the numeric point of view, and ill-conditioned from the symbolic point of view. We exhibit a polynomial-time numeric algorithm solving any member of this family, which significantly contrasts the exponential behavior of all known symbolic algorithms solving a generic instance of this family of systems. © 2005 Elsevier Inc. All rights reserved.
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Bank, B. - Giusti, M. - Heintz, J. - Pardo, L.M.
J. Complexity 2005;21(4):377-412
2005
Temas: Arithmetic circuit - Arithmetic network - Complexity - Elimination procedure - Geometric degree - Geometry of polar varieties and its generalizations - Real polynomial equation solving - Algorithms - Computational complexity - Digital arithmetic
Descripción: Let V be a closed algebraic subvariety of the n-dimensional projective space over the complex or real numbers and suppose that V is non-empty and equidimensional. The classic notion of a polar variety of V associated with a given linear subvariety of the ambient space of V was generalized and motivated in Bank et al. (Kybernetika 40 (2004), to appear). As particular instances of this notion of a generalized polar variety one reobtains the classic one and an alternative type of a polar variety, called dual. As main result of the present paper we show that for a generic choice of their parameters the generalized polar varieties of V are empty or equidimensional and smooth in any regular point of V. In the case that the variety V is affine and smooth and has a complete intersection ideal of definition, we are able, for a generic parameter choice, to describe locally the generalized polar varieties of V by explicit equations. Finally, we indicate how this description may be used in order to design in the context of algorithmic elimination theory a highly efficient, probabilistic elimination procedure for the following task: In case, that the variety V is ℚ-definable and affine, having a complete intersection ideal of definition, and that the real trace of V is non-empty and smooth, find for each connected component of the real trace of V an algebraic sample point. © 2005 Elsevier Inc. All rights reserved.
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Braberman, V. - Olivero, A. - Schapachnik, F.
Electron. Notes Theor. Comput. Sci. 2002;68(4):503-522
2002
Temas: Automata theory - Computation theory - Computer architecture - Computer software - Graph theory - Mathematical models - Matrix algebra - Problem solving - Program processors - Real time systems
Descripción: In this work we present Zeus, a Distributed Model-Checker that evolves from the tool Kronos [8] and that currently can handle backwards computation of TCTL-reachability properties [1] over timed-automata [2]. Zeus was developed following a software architecture centric approach. It introduces some interesting features such as a priori graph partitioning, a sophisticated machinery to reach optimum performance (communication piggybacking and delayed messaging) and dead-time utilization, where every processor uses time intervals of inactivity to perform auxiliary, time-consuming tasks that will later speed up the rest of the computation. Although some good results have been obtained, early experiments pinpointed the difficulties of getting speedups using a parallel asynchronous version. We also propose some paths to overcome those obstacles. We would like to thank Sergio Yovine for making Kronos libraries available to us. © 2002 Published by Elsevier Science B.V.
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