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Density matrices are powerful mathematical tools for the description of closed and open quantum systems. Recently, methods for the direct computation of density matrix elements in scalar quantum field theory were developed based on thermo…

High Energy Physics - Theory · Physics 2025-03-12 Christian Käding , Mario Pitschmann

We extend our finite difference time domain method for numerical solution of the Schrodinger equation to cases where eigenfunctions are complex-valued. Illustrative numerical results for an electron in two dimensions, subject to a confining…

Computational Physics · Physics 2008-07-05 I. Wayan Sudiarta , D. J. Wallace Geldart

Based on the real-time formalism, especially, on Thermo Field Dynamics, we derive the Schwinger-Dyson gap equation for the fermion propagator in QED and Four-Fermion model at finite-temperature and -density. We discuss some advantage of the…

High Energy Physics - Theory · Physics 2015-06-26 K. -I. Kondo , K. Yoshida

The time-dependent Dirac equation is solved using the three-dimensional Finite Difference-Time Domain (FDTD) method. The dynamics of the electron wave packet in a scalar potential is studied in the arrangements associated with the Klein…

Quantum Physics · Physics 2009-01-26 Neven Simicevic

Quantifying the effects of finite temperature and density (FTD) on particle properties is essential for understanding phenomena within and beyond the Standard Model. In this work, we present a simplified framework for calculating particle…

High Energy Physics - Phenomenology · Physics 2025-07-22 Nirmalya Brahma , Saniya Heeba , Hugo Schérer , Katelin Schutz

To enhance the scalability and performance of the traditional finite-difference time-domain (FDTD) methods, a three-dimensional summation-by-parts simultaneous approximation term (SBP-SAT) FDTD method is developed to solve complex…

Computational Engineering, Finance, and Science · Computer Science 2022-06-02 Yu Cheng , Hanhong Liu , Xinsong Wang , Guangzhi Chen , Xiang-Hua Wang , Xingqi Zhang , Shunchuan Yang , Zhizhang Chen

We extend the publicly available quantumfdtd code. It was originally intended for solving the time-independent three-dimensional Schr\"odinger equation via the finite-difference time-domain (FDTD) method and for extracting the ground,…

High Energy Physics - Phenomenology · Physics 2023-01-02 Rafael L. Delgado , Sebastian Steinbeißer , Michael Strickland , Johannes H. Weber

A Gaussian resolution method for the computation of equilibrium density matrices rho(T) for a general multidimensional quantum problem is presented. The variational principle applied to the ``imaginary time'' Schroedinger equation provides…

Quantum Physics · Physics 2009-11-10 P. Frantsuzov , A. Neumaier , V. A. Mandelshtam

A fast and stable numerical method is formulated to compute the time evolution of a wave function in a magnetic field by solving the time-dependent Schroedinger equation. This computational method is based on the finite element method in…

Computational Physics · Physics 2009-11-06 Naoki Watanabe , Masaru Tsukada

Simulation of 3D low-frequency electromagnetic fields propagating in the Earth is computationally expensive. We present a fictitious wave domain high-order finite-difference time-domain (FDTD) modelling method on nonuniform grids to compute…

Numerical Analysis · Mathematics 2023-02-13 Pengliang Yang , Rune Mittet

In this paper, we study numerical approximations of the ground states in finite temperature density functional theory. We formulate the problem with respect to the density matrices and justify the convergence of the finite dimensional…

Numerical Analysis · Mathematics 2024-05-14 Ge Xu , Huajie Chen , Xingyu Gao

We present a time domain method to solve quantum scattering by an arbitrary potential of finite range. The scattering wave function in full space can be obtained, including the near field, the mid field (i.e. Fresnel region) and the far…

Quantum Physics · Physics 2024-12-31 Kun Chen

A numerical model based on the finite-difference time-domain (FDTD) method is developed to simulate thermal noise in open cavities owing to output coupling. The absorbing boundary of the FDTD grid is treated as a blackbody, whose thermal…

Optics · Physics 2009-05-28 Jonathan Andreasen , Hui Cao , Allen Taflove , Prem Kumar , Chang-qi Cao

We give graphical rules, based on earlier work for the functional Schrodinger equation, for constructing the density matrix for scalar and gauge fields at finite temperature T. More useful is a dimensionally-reduced effective action (DREA)…

High Energy Physics - Theory · Physics 2009-11-07 C. A. A. de Carvalho , John M. Cornwall , A. J. da Silva

This paper describes a numerical formulation for calculating wave propagation with high precision in a three-dimensional system. Yee's discretization scheme is used to formulate a frequency domain method that is compatible with the…

Computational Physics · Physics 2013-02-21 Tatsuya Usuki

This paper proposes an efficient FDTD technique for determining electromagnetic fields interacting with a finite-sized 2D and 3D periodic structures. The technique combines periodic boundary conditions---modelling fields away from the edges…

Computational Engineering, Finance, and Science · Computer Science 2024-10-30 Aaron J. Kogon , Costas D. Sarris

X-ray Thomson scattering (XRTS) constitutes an essential technique for diagnosing material properties under extreme conditions, such as high pressures and intense laser heating. Time-dependent density functional theory (TDDFT) is one of the…

Ultra-fast electronic phenomena originating from finite temperature, such as nonlinear optical excitation, can be simulated with high fidelity via real-time time dependent density functional theory (rt-TDDFT) calculations with hybrid…

Materials Science · Physics 2025-01-07 Rongrong Liu , Zhuoqiang Guo , Qiuchen Sha , Tong Zhao , Haibo Li , Wei Hu , Lijun Liu , Guangming Tan , Weile Jia

A finite-difference time-domain (FDTD) modelling of finite-size zero thickness space-time modulated Huygens' metasurfaces based on Generalized Sheet Transition Conditions (GSTCs), is proposed and numerically demonstrated. A typical…

Optics · Physics 2017-01-06 Scott A. Stewart , Tom J. Smy , Shulabh Gupta

This paper establishes a far-reaching connection between the Finite-Difference Time-Domain method (FDTD) and the theory of dissipative systems. The FDTD equations for a rectangular region are written as a dynamical system having the…

Computational Engineering, Finance, and Science · Computer Science 2017-04-05 Fadime Bekmambetova , Xinyue Zhang , Piero Triverio