The Experts below are selected from a list of 1356 Experts worldwide ranked by ideXlab platform
Thomas Gasenzer - One of the best experts on this subject based on the ideXlab platform.
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buildup of the kondo effect from real time effective action for the anderson impurity model
Physical Review B, 2016Co-Authors: Sebastian Bock, Alexander Liluashvili, Thomas GasenzerAbstract:The nonequilibrium time evolution of a quantum dot is studied by means of dynamic equations for timedependent Greens Functions derived from a two-particle-irreducible (2PI) e ective action for the Anderson impurity model. Coupling the dot between two leads at di erent voltages, the dynamics of the current through the dot is investigated. We show that the 2PI approach is capable to describe the dynamical build-up of the Kondo e ect, which shows up as a sharp resonance in the spectral function, with a width exponentially suppressed in the electron self coupling on the dot. An external voltage applied to the dot is found to deteriorate the Kondo e ect at the hybridization scale. The dynamic equations are evaluated within di erent nonperturbative resummation schemes, within the direct, particle-particle, and particle-hole channels, as well as their combination, and the results compared with that from other methods.
Karthik Duraisamy - One of the best experts on this subject based on the ideXlab platform.
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variational multiscale closures for finite element discretizations using the mori zwanzig approach
arXiv: Computational Physics, 2019Co-Authors: Aniruddhe Pradhan, Karthik DuraisamyAbstract:Simulation of multiscale problems remains a challenge due to the disparate range of spatial and temporal scales and the complex interaction between the resolved and unresolved scales. This work develops a coarse-grained modeling approach for the Continuous Galerkin discretizations by combining the Variational Multiscale decomposition and the Mori-Zwanzig (M-Z) formalism. An appeal of the M-Z formalism is that - akin to Greens Functions for linear problems - the impact of unresolved dynamics on resolved scales can be formally represented as a convolution (or memory) integral in a non-linear setting. To ensure tractable and efficient models, Markovian closures are developed for the M-Z memory integral. The resulting sub-scale model has some similarities to adjoint stabilization and orthogonal subscale models. The model is made parameter free by adaptively determining the memory length during the simulation. To illustrate the generalizablity of this model, it is employed in coarse-grained simulations for the one-dimensional Burgers equation and in incompressible turbulence problems.
Vinod K. Tewary - One of the best experts on this subject based on the ideXlab platform.
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Greens Functions for boundary element analysis of anisotropic bimaterials
Engineering Analysis With Boundary Elements, 2001Co-Authors: John Berger, Vinod K. TewaryAbstract:We present several Greens Functions for anisotropic bimaterials for two-dimensional elasticity and steady-state heat transfer problems. The details of the various Greens Functions for perfect, slipping, and cracked interfaces are given for mechanical loading conditions. Previously reported formulations for cubic materials are extended to materials with general anisotropy in which plane strain deformations can exist. We also give the steady-state Greens function for thermal loading of a bimaterial with a perfectly bonded interface. The Greens Functions are incorporated in boundary integral formulations and method of fundamental solutions formulations for analysis of finite solids under general boundary conditions.
Sebastian Bock - One of the best experts on this subject based on the ideXlab platform.
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buildup of the kondo effect from real time effective action for the anderson impurity model
Physical Review B, 2016Co-Authors: Sebastian Bock, Alexander Liluashvili, Thomas GasenzerAbstract:The nonequilibrium time evolution of a quantum dot is studied by means of dynamic equations for timedependent Greens Functions derived from a two-particle-irreducible (2PI) e ective action for the Anderson impurity model. Coupling the dot between two leads at di erent voltages, the dynamics of the current through the dot is investigated. We show that the 2PI approach is capable to describe the dynamical build-up of the Kondo e ect, which shows up as a sharp resonance in the spectral function, with a width exponentially suppressed in the electron self coupling on the dot. An external voltage applied to the dot is found to deteriorate the Kondo e ect at the hybridization scale. The dynamic equations are evaluated within di erent nonperturbative resummation schemes, within the direct, particle-particle, and particle-hole channels, as well as their combination, and the results compared with that from other methods.
Aniruddhe Pradhan - One of the best experts on this subject based on the ideXlab platform.
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variational multiscale closures for finite element discretizations using the mori zwanzig approach
arXiv: Computational Physics, 2019Co-Authors: Aniruddhe Pradhan, Karthik DuraisamyAbstract:Simulation of multiscale problems remains a challenge due to the disparate range of spatial and temporal scales and the complex interaction between the resolved and unresolved scales. This work develops a coarse-grained modeling approach for the Continuous Galerkin discretizations by combining the Variational Multiscale decomposition and the Mori-Zwanzig (M-Z) formalism. An appeal of the M-Z formalism is that - akin to Greens Functions for linear problems - the impact of unresolved dynamics on resolved scales can be formally represented as a convolution (or memory) integral in a non-linear setting. To ensure tractable and efficient models, Markovian closures are developed for the M-Z memory integral. The resulting sub-scale model has some similarities to adjoint stabilization and orthogonal subscale models. The model is made parameter free by adaptively determining the memory length during the simulation. To illustrate the generalizablity of this model, it is employed in coarse-grained simulations for the one-dimensional Burgers equation and in incompressible turbulence problems.
