Browsing by Author "Lu, Jianfeng"
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A Hybrid Globallocal Numerical Method for Multiscale PDEs
Huang, Y; Lu, Jianfeng; Ming, P (20170423)We present a new hybrid numerical method for multiscale partial differential equations, which simultaneously captures both the global macroscopic information and resolves the local microscopic events. The convergence of ... 
A Variation on the DonskerVaradhan Inequality for the Principial Eigenvalue
Lu, Jianfeng; Steinerberger, Stefan (20170423)The purpose of this short note is to give a variation on the classical DonskerVaradhan inequality, which bounds the first eigenvalue of a secondorder elliptic operator on a bounded domain $\Omega$ by the largest mean first ... 
Accelerated sampling by infinite swapping of path integral molecular dynamics with surface hopping
Lu, Jianfeng; Zhou, Zhennan (20171130)To accelerate the thermal equilibrium sampling of multilevel quantum systems, the infinite swapping limit of a recently proposed multilevel ring polymer representation is investigated. In the infinite swapping limiting, ... 
An isoperimetric problem with Coulomb repulsion and attraction to a background nucleus
Lu, Jianfeng; Otto, Felix (20170423)We study an isoperimetric problem the energy of which contains the perimeter of a set, Coulomb repulsion of the set with itself, and attraction of the set to a background nucleus as a point charge with charge $Z$. For the ... 
Bloch dynamics with second order Berry phase correction
Lu, Jianfeng; Zhang, Zihang; Zhou, Zhennan (20170423)We derive the semiclassical Bloch dynamics with the second order Berry phase correction, based on a twoscale WKB asymptotic analysis. For uniform external electric field, the bicharacteristics system after a positional ... 
Bold Diagrammatic Monte Carlo in the Lens of Stochastic Iterative Methods
Li, Yingzhou; Lu, Jianfeng (20171130)This work aims at understanding of bold diagrammatic Monte Carlo (BDMC) methods for stochastic summation of Feynman diagrams from the angle of stochastic iterative methods. The convergence enhancement trick of the BDMC is ... 
Complexity of randomized algorithms for underdamped Langevin dynamics
Cao, Yu; Lu, Jianfeng; Wang, LihanWe establish an information complexity lower bound of randomized algorithms for simulating underdamped Langevin dynamics. More specifically, we prove that the worst $L^2$ strong error is of order $\Omega(\sqrt{d}\, N^{3/2})$, ... 
Defect resonances of truncated crystal structures
Lu, Jianfeng; Marzuola, Jeremy L; Watson, Alexander BDefects in the atomic structure of crystalline materials may spawn electronic bound states, known as \emph{defect states}, which decay rapidly away from the defect. Simplified models of defect states typically assume the ... 
Efficient construction of tensor ring representations from sampling
Khoo, Yuehaw; Lu, Jianfeng; Ying, Lexing (20171130)In this note we propose an efficient method to compress a high dimensional function into a tensor ring format, based on alternating leastsquares (ALS). Since the function has size exponential in $d$ where $d$ is the number ... 
Emergence of step flow from an atomistic scheme of epitaxial growth in 1+1 dimensions.
Lu, Jianfeng; Liu, JianGuo; Margetis, Dionisios (Phys Rev E Stat Nonlin Soft Matter Phys, 201503)The BurtonCabreraFrank (BCF) model for the flow of line defects (steps) on crystal surfaces has offered useful insights into nanostructure evolution. This model has rested on phenomenological grounds. Our goal is to show ... 
Existence and computation of generalized Wannier functions for nonperiodic systems in two dimensions and higher
Stubbs, Kevin D; Watson, Alexander B; Lu, JianfengExponentiallylocalized Wannier functions (ELWFs) are a basis of the Fermi projection of a material consisting of functions which decay exponentially fast away from their maxima. When the material is insulating ... 
Fast algorithm for periodic density fitting for Bloch waves
Lu, Jianfeng; Ying, Lexing (20170423)We propose an efficient algorithm for density fitting of Bloch waves for Hamiltonian operators with periodic potential. The algorithm is based on column selection and random Fourier projection of the orbital functions. The ... 
Fractional stochastic differential equations satisfying fluctuationdissipation theorem
Li, L; Liu, JG; Lu, Jianfeng (20170423)We consider in this work stochastic differential equation (SDE) model for particles in contact with a heat bath when the memory effects are nonnegligible. As a result of the fluctuationdissipation theorem, the differential ... 
Global optimality of softmax policy gradient with single hidden layer neural networks in the meanfield regime
Agazzi, Andrea; Lu, JianfengWe study the problem of policy optimization for infinitehorizon discounted Markov Decision Processes with softmax policy and nonlinear function approximation trained with policy gradient algorithms. We concentrate ... 
Improved sampling and validation of frozen Gaussian approximation with surface hopping algorithm for nonadiabatic dynamics.
Lu, Jianfeng; Zhou, Zhennan (J Chem Phys, 20160928)In the spirit of the fewest switches surface hopping, the frozen Gaussian approximation with surface hopping (FGASH) method samples a path integral representation of the nonadiabatic dynamics in the semiclassical regime. ... 
Infinite swapping replica exchange molecular dynamics leads to a simple simulation patch using mixture potentials.
Lu, Jianfeng; VandenEijnden, Eric (J Chem Phys, 20130228)Replica exchange molecular dynamics (REMD) becomes more efficient as the frequency of swap between the temperatures is increased. Recently Plattner et al. [J. Chem. Phys. 135, 134111 (2011)] proposed a method to implement ... 
NonConvex Planar Harmonic Maps
Kovalsky, Shahar Z; Aigerman, Noam; Daubechies, Ingrid; Kazhdan, Michael; Lu, Jianfeng; Steinerberger, StefanWe formulate a novel characterization of a family of invertible maps between twodimensional domains. Our work follows two classic results: The Rad\'oKneserChoquet (RKC) theorem, which establishes the invertibility of harmonic ... 
Numerical methods for stochastic differential equations based on Gaussian mixture
Li, Lei; Lu, Jianfeng; Mattingly, Jonathan; Wang, LihanWe develop in this work a numerical method for stochastic differential equations (SDEs) with weak second order accuracy based on Gaussian mixture. Unlike the conventional higher order schemes for SDEs based on It\^oTayl... 
On discrete Wigner transforms
Cai, Zhenning; Lu, Jianfeng; Stubbs, KevinIn this work, we derive a discrete analog of the Wigner transform over the space $(\mathbb{C}^p)^{\otimes N}$ for any prime $p$ and any positive integer $N$. We show that the Wigner transform over this space can be constructed ... 
On explicit $L^2$convergence rate estimate for piecewise deterministic Markov processes
Lu, Jianfeng; Wang, LihanWe establish $L^2$exponential convergence rate for three popular piecewise deterministic Markov processes for sampling: the randomized Hamiltonian Monte Carlo method, the zigzag process, and the bouncy particle sampler. ...