The Experts below are selected from a list of 110142 Experts worldwide ranked by ideXlab platform
Herbert Weigel - One of the best experts on this subject based on the ideXlab platform.
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Weak Isospin Symmetry and the Vacuum Polarization Energy of Cosmic Strings
Proceedings, 2018Co-Authors: Herbert WeigelAbstract:The vacuum Polarization Energy is the leading quantum correction to the Energy of a localized field configuration. [...]
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Vacuum Polarization Energy of the Shifman–Voloshin soliton
Physics Letters B, 2018Co-Authors: Herbert Weigel, Noah GrahamAbstract:Abstract We compute the vacuum Polarization Energy of soliton configurations in a model with two scalar fields in one space dimension using spectral methods. The second field represents an extension of the conventional ϕ 4 kink soliton model. We find that the vacuum Polarization Energy destabilizes the soliton except when the fields have identical masses. In that case the model is equivalent to two independent ϕ 4 models.
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emerging translational variance vacuum Polarization Energy of the kink
Advances in High Energy Physics, 2017Co-Authors: Herbert WeigelAbstract:We propose an efficient method to compute the vacuum Polarization Energy of static field configurations that do not allow decomposition into symmetric and antisymmetric channels in one space dimension. In particular, we compute the vacuum Polarization Energy of the kink soliton in the model. We link the dependence of this Energy on the position of the center of the soliton to the different masses of the quantum fluctuations at negative and positive spatial infinity.
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Vacuum Polarization Energy of the $\mathbf{\phi^6}$ kink
arXiv: High Energy Physics - Theory, 2017Co-Authors: Herbert WeigelAbstract:We propose an efficient method to compute the vacuum Polarization Energy of static field configurations that do not allow a decomposition into symmetric and anti-symmetric channels in one space dimension. In particular we compute the vacuum Polarization Energy of the kink soliton in the $\phi^6$ model. We link the dependence of this Energy on the position of the center of the soliton to the different masses of the quantum fluctuations at negative and positive spatial infinity.
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emerging translational variance vacuum Polarization Energy of the mathbf phi 6 kink
arXiv: High Energy Physics - Theory, 2017Co-Authors: Herbert WeigelAbstract:We propose an efficient method to compute the vacuum Polarization Energy of static field configurations that do not allow a decomposition into symmetric and anti-symmetric channels in one space dimension. In particular we compute the vacuum Polarization Energy of the kink soliton in the $\phi^6$ model. We link the dependence of this Energy on the position of the center of the soliton to the different masses of the quantum fluctuations at negative and positive spatial infinity.
De-fu Hou - One of the best experts on this subject based on the ideXlab platform.
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Polarization Energy loss in hot viscous quark–gluon plasma
Journal of Physics G: Nuclear and Particle Physics, 2015Co-Authors: Bing-feng Jiang, De-fu HouAbstract:The gluon Polarization tensor for quark–gluon plasma with shear viscosity is derived with the viscous chromohydrodynamics. The longitudinal and transverse dielectric functions are evaluated from the gluon Polarization tensor, through which the Polarization Energy loss suffered by a fast quark traveling through the viscous quark–gluon plasma is investigated. The numerical analysis indicates that shear viscosity significantly reduces the Polarization Energy loss.
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Polarization Energy loss in hot viscous quark-gluon plasma
arXiv: High Energy Physics - Phenomenology, 2014Co-Authors: Bing-feng Jiang, De-fu HouAbstract:The gluon Polarization tensor for the quark-gluon plasma with shear viscosity is derived with the viscous chromohydrodynamics. The longitudinal and transverse dielectric functions are evaluated from the gluon Polarization tensor, through which the Polarization Energy loss suffered by a fast quark traveling through the viscous quark-gluon plasma is investigated. The numerical analysis indicates that shear viscosity significantly reduces the Polarization Energy loss.
Noah Graham - One of the best experts on this subject based on the ideXlab platform.
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Vacuum Polarization Energy of the Shifman–Voloshin soliton
Physics Letters B, 2018Co-Authors: Herbert Weigel, Noah GrahamAbstract:Abstract We compute the vacuum Polarization Energy of soliton configurations in a model with two scalar fields in one space dimension using spectral methods. The second field represents an extension of the conventional ϕ 4 kink soliton model. We find that the vacuum Polarization Energy destabilizes the soliton except when the fields have identical masses. In that case the model is equivalent to two independent ϕ 4 models.
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Isospin Invariance and the Vacuum Polarization Energy of Cosmic Strings
Physical Review D, 2016Co-Authors: Herbert Weigel, Markus Quandt, Noah GrahamAbstract:We corroborate the previously applied spectral approach to compute the vacuum Polarization Energy of string configurations in models similar to the standard model of particle physics. The central observation underlying this corroboration is the existence of a particular global isospin transformation of the string configuration. Under this transformation the single particle energies of the quantum fluctuations are invariant, while the inevitable implementation of regularization and renormalization requires operations that are not invariant. We verify numerically that all such variances eventually cancel, and that the vacuum Polarization Energy obtained in the spectral approach is indeed gauge invariant.
Bing-feng Jiang - One of the best experts on this subject based on the ideXlab platform.
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Polarization Energy loss in hot viscous quark–gluon plasma
Journal of Physics G: Nuclear and Particle Physics, 2015Co-Authors: Bing-feng Jiang, De-fu HouAbstract:The gluon Polarization tensor for quark–gluon plasma with shear viscosity is derived with the viscous chromohydrodynamics. The longitudinal and transverse dielectric functions are evaluated from the gluon Polarization tensor, through which the Polarization Energy loss suffered by a fast quark traveling through the viscous quark–gluon plasma is investigated. The numerical analysis indicates that shear viscosity significantly reduces the Polarization Energy loss.
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Polarization Energy loss in hot viscous quark-gluon plasma
arXiv: High Energy Physics - Phenomenology, 2014Co-Authors: Bing-feng Jiang, De-fu HouAbstract:The gluon Polarization tensor for the quark-gluon plasma with shear viscosity is derived with the viscous chromohydrodynamics. The longitudinal and transverse dielectric functions are evaluated from the gluon Polarization tensor, through which the Polarization Energy loss suffered by a fast quark traveling through the viscous quark-gluon plasma is investigated. The numerical analysis indicates that shear viscosity significantly reduces the Polarization Energy loss.
Jean-philip Piquemal - One of the best experts on this subject based on the ideXlab platform.
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Truncated Conjugate Gradient (TCG): an optimal strategy for the analytical evaluation of the many-body Polarization Energy and forces in molecular simulations
Journal of Chemical Theory and Computation, 2017Co-Authors: Félix Aviat, Louis Lagardère, Benjamin Stamm, Pengyu Ren, Yvon Maday, Antoine Levitt, Jay W. Ponder, Jean-philip PiquemalAbstract:We introduce a new class of methods, denoted as Truncated Conjugate Gradient (TCG) methods, to solve the many-body Polarization Energy and its associated forces in molecular simulations encountered in molecular dynamics (MD) and Monte-Carlo techniques. The method consists of a fixed number of Conjugate Gradient (CG) iterations. TCG approaches provide a scalable solution to the Polarization problem at a user-chosen cost and a corresponding optimal accuracy and complexity. The optimality of the CG-method guarantees that the number of the required matrix-vector products are reduced to a minimum compared to other iterative methods. This family of methods is non empirical, fully adaptive and provides analytical gradients, avoiding therefore any Energy drift in MD as compared to popular iterative solvers. Besides speed, one great advantage of this class of approximate methods is that their accuracy is systematically improvable. Indeed, as the CG-method is a Krylov subspace method, the associated error is monotonically reduced at each iteration. On top of that, two improvements can be proposed at virtually no cost: (i) the use of preconditioners can be employed, which leads to the Truncated Preconditioned Conjugate Gradient (TPCG); (ii) since the residual of the final step of the CG-method is available, one additional Picard fixed point iteration ("peek"), equivalent to one step of Jacobi Over Relaxation (JOR) with relaxation parameter omega, can be made at almost no cost. This method is denoted by TCG-n(omega). Black box adaptive methods to find omega are provided and discussed. Results show that TPCG-3(omega) is converged to high accuracy for various types of systems including proteins and highly charged systems at the fixed cost of 4 matrix-vector products: (3 CG iterations+the initial CG descent direction) whereas T(P)CG-2(omega) provides robust results at a reduced cost (3 matrix-vector products) and offers new perspectives for long polarizable MD as a production algorithm. The T(P)CG-1(omega) level provides less accurate solutions for inhomogeneous systems, but its applicability to well-conditioned problems such as water is remarkable, with only two matrix-vector product evaluations.
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Truncated Conjugate Gradient: An Optimal Strategy for the Analytical Evaluation of the Many-Body Polarization Energy and Forces in Molecular Simulations.
Journal of chemical theory and computation, 2016Co-Authors: Félix Aviat, Louis Lagardère, Benjamin Stamm, Pengyu Ren, Yvon Maday, Antoine Levitt, Jay W. Ponder, Jean-philip PiquemalAbstract:We introduce a new class of methods, denoted as Truncated Conjugate Gradient(TCG), to solve the many-body Polarization Energy and its associated forces in molecular simulations (i.e. molecular dynamics (MD) and Monte Carlo). The method consists in a fixed number of Conjugate Gradient (CG) iterations. TCG approaches provide a scalable solution to the Polarization problem at a user-chosen cost and a corresponding optimal accuracy. The optimality of the CG-method guarantees that the number of the required matrix-vector products are reduced to a minimum compared to other iterative methods. This family of methods is non-empirical, fully adaptive, and provides analytical gradients, avoiding therefore any Energy drift in MD as compared to popular iterative solvers. Besides speed, one great advantage of this class of approximate methods is that their accuracy is systematically improvable. Indeed, as the CG-method is a Krylov subspace method, the associated error is monotonically reduced at each iteration. On top ...
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Scalable Evaluation of Polarization Energy and Associated Forces in Polarizable Molecular Dynamics: I. Toward Massively Parallel Direct Space Computations
Journal of chemical theory and computation, 2014Co-Authors: Filippo Lipparini, Louis Lagardère, Benjamin Stamm, Eric Cancès, Michael J. Schnieders, Pengyu Ren, Yvon Maday, Jean-philip PiquemalAbstract:In this paper, we investigate various numerical strategies to compute the direct space Polarization Energy and associated forces in the context of the point dipole approximation (including damping) used in polarizable molecular dynamics. We present a careful mathematical analysis of the algorithms that have been implemented in popular production packages and applied to large test systems. We show that the classical Jacobi Over-Relaxation method (JOR) should not be used as its convergence requires a proper value of the relaxation parameter, whereas other strategies should be preferred. On a single node, Preconditioned Conjugate Gradient methods (PCG) and Jacobi algorithm coupled with the Direct Inversion in the Iterative Subspace (JI/DIIS) provide reliable stability/convergence and are roughly twice as fast as JOR. Moreover, both algorithms are suitable for massively parallel implementations. The lower requirements in terms of processes communications make JI/DIIS the method of choice for MPI and hybrid Op...
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Key Role of the Polarization Anisotropy of Water in Modeling Classical Polarizable Force Fields
The journal of physical chemistry. A, 2007Co-Authors: Jean-philip Piquemal, Riccardo Chelli, Piero Procacci, Nohad GreshAbstract:We have evaluated the extent to which classical polarizable force fields, based either on the chemical potential equalization principle or on distributed polarizabilities in the framework of the Sum of Interactions Between Fragments Ab initio computed (SIBFA), can reproduce the ab initio Polarization Energy and the dipole moment of three distinct water oligomers: bifurcated chains, transverse hydrogen-bonded chains, and longitudinal hydrogen-bonded chains of helical shape. To analyze the many-body Polarization effect, chains of different size, i.e., from 2 to 12 water monomers, have been considered. Although the dipole moment is a well-defined quantity in both classical polarizable models and quantum mechanical methods, Polarization Energy can be defined unequivocally only in the former type of approaches. In this study we have used the Kitaura-Morokuma (KM) procedure. Although the KM approach is on the one hand known to overestimate the Polarization Energy for strongly interacting molecules, on the other hand it can account for the many-body Polarization effectively, whereas some other procedures do not. Our data show that, if off-centered lone pair polarizabilities are explicitly represented, classical polarizable force fields can afford a close agreement with the ab initio results, both in terms of Polarization Energy and in terms of dipole moment.