The Experts below are selected from a list of 273 Experts worldwide ranked by ideXlab platform
Daniel Neuhauser - One of the best experts on this subject based on the ideXlab platform.
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Simple Eigenvalue-self-consistent Δ¯GW0.
The Journal of chemical physics, 2018Co-Authors: Vojtěch Vlček, Roi Baer, Eran Rabani, Daniel NeuhauserAbstract:We show that a rigid scissors-like GW self-consistency approach, labeled here Δ¯GW0, can be trivially implemented at zero additional cost for large scale one-shot G0W0 calculations. The method significantly improves one-shot G0W0 and for large systems is very accurate. Δ¯GW0 is similar in spirit to evGW0 where the self-consistency is only applied on the Eigenvalues entering Green’s function, while both W and the eigenvectors of Green’s function are held fixed. Δ¯GW0 further assumes that the shift of the Eigenvalues is rigid scissors-like so that all occupied states are shifted by the same amount and analogously for all the unoccupied states. We show that this results in a trivial modification of the time-dependent G0W0 self-energy, enabling an a posteriori self-consistency cycle. The method is applicable for our recent stochastic-GW approach, thereby enabling self-consistent calculations for giant systems with thousands of electrons. The accuracy of Δ¯GW0 increases with the system size. For molecules, it is up to 0.4-0.5 eV away from coupled-cluster single double triple (CCSD(T)), but for tetracene and hexacene, it matches the ionization energies from both CCSD(T) and evGW0 to better than 0.05 eV. For solids, as exemplified here by periodic supercells of semiconductors and insulators with 6192 valence electrons, the method matches evGW0 quite well and both methods are in good agreement with the experiment.We show that a rigid scissors-like GW self-consistency approach, labeled here Δ¯GW0, can be trivially implemented at zero additional cost for large scale one-shot G0W0 calculations. The method significantly improves one-shot G0W0 and for large systems is very accurate. Δ¯GW0 is similar in spirit to evGW0 where the self-consistency is only applied on the Eigenvalues entering Green’s function, while both W and the eigenvectors of Green’s function are held fixed. Δ¯GW0 further assumes that the shift of the Eigenvalues is rigid scissors-like so that all occupied states are shifted by the same amount and analogously for all the unoccupied states. We show that this results in a trivial modification of the time-dependent G0W0 self-energy, enabling an a posteriori self-consistency cycle. The method is applicable for our recent stochastic-GW approach, thereby enabling self-consistent calculations for giant systems with thousands of electrons. The accuracy of Δ¯GW0 increases with the system size. For molecules, it ...
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Simple Eigenvalue self consistent δ gw0
Journal of Chemical Physics, 2018Co-Authors: Vojtěch Vlček, Roi Baer, Eran Rabani, Daniel NeuhauserAbstract:We show that a rigid scissors-like GW self-consistency approach, labeled here Δ¯GW0, can be trivially implemented at zero additional cost for large scale one-shot G0W0 calculations. The method significantly improves one-shot G0W0 and for large systems is very accurate. Δ¯GW0 is similar in spirit to evGW0 where the self-consistency is only applied on the Eigenvalues entering Green’s function, while both W and the eigenvectors of Green’s function are held fixed. Δ¯GW0 further assumes that the shift of the Eigenvalues is rigid scissors-like so that all occupied states are shifted by the same amount and analogously for all the unoccupied states. We show that this results in a trivial modification of the time-dependent G0W0 self-energy, enabling an a posteriori self-consistency cycle. The method is applicable for our recent stochastic-GW approach, thereby enabling self-consistent calculations for giant systems with thousands of electrons. The accuracy of Δ¯GW0 increases with the system size. For molecules, it is up to 0.4-0.5 eV away from coupled-cluster single double triple (CCSD(T)), but for tetracene and hexacene, it matches the ionization energies from both CCSD(T) and evGW0 to better than 0.05 eV. For solids, as exemplified here by periodic supercells of semiconductors and insulators with 6192 valence electrons, the method matches evGW0 quite well and both methods are in good agreement with the experiment.We show that a rigid scissors-like GW self-consistency approach, labeled here Δ¯GW0, can be trivially implemented at zero additional cost for large scale one-shot G0W0 calculations. The method significantly improves one-shot G0W0 and for large systems is very accurate. Δ¯GW0 is similar in spirit to evGW0 where the self-consistency is only applied on the Eigenvalues entering Green’s function, while both W and the eigenvectors of Green’s function are held fixed. Δ¯GW0 further assumes that the shift of the Eigenvalues is rigid scissors-like so that all occupied states are shifted by the same amount and analogously for all the unoccupied states. We show that this results in a trivial modification of the time-dependent G0W0 self-energy, enabling an a posteriori self-consistency cycle. The method is applicable for our recent stochastic-GW approach, thereby enabling self-consistent calculations for giant systems with thousands of electrons. The accuracy of Δ¯GW0 increases with the system size. For molecules, it ...
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Simple Eigenvalue self consistent bar delta gw_ 0
arXiv: Chemical Physics, 2017Co-Authors: Vojtěch Vlček, Roi Baer, Eran Rabani, Daniel NeuhauserAbstract:We derive a general form of Eigenvalue self-consistency for $GW_{0}$ in the time domain and use it to obtain a simplified postprocessing Eigenvalue self-consistency, which we label $\bar{\Delta}GW_{0}$. The method costs the same as a one-shot $G_{0}W_{0}$ when the latter gives the full frequency-domain (or time-domain) matrix element of the self-energy. The accuracy of $\bar{\Delta}GW_{0}$ increases with system size, as demonstrated here by comparison to other $GW$ self-consistency results and to CCSD(T) predictions. When combined with the large-scale stochastic $G_{0}W_{0}$ formulation $\bar{\Delta}GW_{0}$ is applicable to very large systems, as exemplified by periodic supercells of semiconductors and insulators with 2048 valence electrons. For molecules the error of our eventual partially self-consistent approach starts at about 0.2eV for small molecules and decreases to 0.05eV for large ones, while for the periodic solids studied here the mean-absolute-error is only 0.03eV.
Giovanni P Galdi - One of the best experts on this subject based on the ideXlab platform.
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on the problem of steady bifurcation of a falling sphere in a navier stokes liquid
Journal of Mathematical Physics, 2020Co-Authors: Giovanni P GaldiAbstract:We study steady bifurcation for the coupled system body-liquid consisting of a sphere freely falling in a Navier–Stokes liquid under the action of gravity. In particular, we show that, under the assumption that for the bifurcating solution, the translational velocity of the sphere is parallel to the gravity, bifurcation takes place, provided that 1 is a Simple Eigenvalue of a suitable linear operator and the transversality property holds. Moreover, we also give sufficient conditions for symmetry breaking.
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on the problem of steady bifurcation of a falling sphere in a navier stokes liquid
arXiv: Analysis of PDEs, 2020Co-Authors: Giovanni P GaldiAbstract:We study steady bifurcation for the coupled system body-liquid consisting of a sphere freely falling in a Navier-Stokes liquid under the action of gravity. In particular we show that, under the assumption that for the bifurcating solution the translational velocity of the sphere is parallel to the gravity, bifurcation takes place provided 1 is a Simple Eigenvalue of a suitable linear operator and the transversality property holds.
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on bifurcating time periodic flow of a navier stokes liquid past a cylinder
arXiv: Analysis of PDEs, 2015Co-Authors: Giovanni P GaldiAbstract:We provide general sufficient conditions for branching out of a time-periodic family of solutions from steady-state solutions to the two-dimensional Navier-Stokes equations in the exterior of a cylinder. To this end, we first show that the problem can be formulated as a coupled elliptic-parabolic nonlinear system in appropriate function spaces. This is obtained by separating the time-independent averaged component of the velocity field from its "purely periodic" one. We then prove that time-periodic bifurcation occurs, provided the linearized time-independent operator of the parabolic problem possess a Simple Eigenvalue that crosses the imaginary axis when the Reynolds number passes through a (suitably defined) critical value. We also show that only supercritical or subcritical bifurcation may occur. Our approach is different and, we believe, more direct than those used by previous authors in similar, but distinct, context.
Ho Woo Lee - One of the best experts on this subject based on the ideXlab platform.
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a Simple Eigenvalue method for low order d bmap g 1 queues
Applied Mathematical Modelling, 2005Co-Authors: Ho Woo Lee, Jong Min Moon, Byung Kyu Kim, Jong Geun Park, Se Won LeeAbstract:This paper is aimed at those engineers and practitioners who need a Simple and understandable non-matrix-analytic procedure to compute the performance measures of the discrete-time BMAP/G/1 queueing system when the order of parameter matrices is very low. We develop a set of system equations and derive the vector generating function of the queue length. Starting from the generating function, we propose a Eigenvalue approach that can be implemented by those who have basic knowledge on M/G/1 queues and Eigenvalue algebra.
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A Simple Eigenvalue method for low-order D-BMAP/G/1 queues
Applied Mathematical Modelling, 2005Co-Authors: Ho Woo Lee, Jong Min Moon, Byung Kyu Kim, Jong Geun Park, Won LeeAbstract:This paper is aimed at those engineers and practitioners who need a Simple and understandable non-matrix-analytic procedure to compute the performance measures of the discrete-time BMAP/G/1 queueing system when the order of parameter matrices is very low. We develop a set of system equations and derive the vector generating function of the queue length. Starting from the generating function, we propose a Eigenvalue approach that can be implemented by those who have basic knowledge on M/G/1 queues and Eigenvalue algebra.
Yuwen Wang - One of the best experts on this subject based on the ideXlab platform.
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Bifurcation from a degenerate Simple Eigenvalue
Journal of Functional Analysis, 2013Co-Authors: Ping Liu, Junping Shi, Yuwen WangAbstract:It is proved that a symmetry-breaking bifurcation occurs at a Simple Eigenvalue despite the usual transversality condition fails, and this bifurcation from a degenerate Simple Eigenvalue result complements the classical one with the transversality condition. The new result is applied to an imperfect pitchfork bifurcation, in which a forward transcritical bifurcation changes to a backward one when the perturbation parameter changes. Several applications in ecological and genetics models are shown.
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Imperfect transcritical and pitchfork bifurcations
Journal of Functional Analysis, 2007Co-Authors: Yuwen WangAbstract:Imperfect bifurcation phenomena are formulated in framework of analytical bifurcation theory on Banach spaces. In particular the perturbations of transcritical and pitchfork bifurcations at a Simple Eigenvalue are examined, and two-parameter unfoldings of singularities are rigorously established. Applications include semilinear elliptic equations, imperfect Euler buckling beam problem and perturbed diffusive logistic equation.
Balmohan V. Limaye - One of the best experts on this subject based on the ideXlab platform.
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ACCELERATED SPECTRAL REFINEMENT PART II: CLUSTER OF EigenvalueS
Anziam Journal, 2000Co-Authors: Rafikul Alam, Rekha P. Kulkarni, Balmohan V. LimayeAbstract:The framework for accelerated spectral refinement for a Simple Eigenvalue developed in Part I of this paper is employed to treat the general case of a cluster of Eigenvalues whose total algebraic multiplicity is finite. Numerical examples concerning the largest and the second largest multiple Eigenvalues of an integral operator are given.
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ACCELERATED SPECTRAL REFINEMENT PART I: Simple Eigenvalue
The Journal of The Australian Mathematical Society. Series B. Applied Mathematics, 2000Co-Authors: Rafikul Alam, Rekha P. Kulkarni, Balmohan V. LimayeAbstract:A general framework is developed for constructing higher order spectral refinement schemes for a Simple Eigenvalue. Well-known techniques for ordinary spectral refinement are carried over to higher order spectral refinement yielding faster rates of convergence. Numerical examples are given by considering an integral operator.
