One-dimensional Schrödinger equation and its “exact” representation on a discrete lattice

Е. А. Соловьев, E. Yankovsky

N. M. Bogoliubov, V. E. Korepin

Liu Xiao-juan, Yi Xiao, Wenhua Hai

The Hamiltonian of one-dimensional chain of n-level atoms is represented in terms of Boson operators by using the Dyson-Maleev transformation and it is shown that the finite-ladder effect disappears when n tends toward infinity. In this way, it is found that the Heisenberg equation of motion of this system is exactly described in the coherent state representation by the dark discrete nonlinear Schrödinger (DNLS) equation. It is also briefly shown that the DNLS equation has some general soliton solutions. This indicates that this simple system has richness of nonlinear waves.

Mashrab E. Akramov, Jambul R. Yusupov, Matthias Ehrhardt +1 more

We construct exact transparent boundary conditions (TBCs) for a time-continuous, spatially discrete Schrödinger equation that models a one-dimensional quantum lattice. Using a recently developed exact solution for the discrete system, we derive the Dirichlet-to-Neumann maps analytically via Laplace transforms. This yields a convolution-type boundary condition governed by Bessel functions. We rigorously demonstrate the consistency of this discrete formulation with its continuous counterpart in the continuum limit. Additionally, we present an efficient time-discretization scheme based on the trapezoidal rule for practical implementation. Numerical experiments using a Crank-Nicolson solver verify that our proposed TBCs eliminate spurious backscattering entirely and preserve reflectionless propagation of a Gaussian wave packet exiting the computational domain

Anadijiban Das, Sourav Haldar

The discrete phase space representation of quantum mechanics involving a characteristic length is investigated. The continuous (1 + 1)-dimensional phase space is first discussed for the sake of simplicity. It is discretized into denumerable infinite number of concentric circles. These circles, endowed with “unit area”, are degenerate phase cells resembling closed strings.Next, Schrödinger wave equation for one particle in the three dimensional space under the influence of a static potential is studied in the discrete phase space representation of wave mechanics. The Schrödinger equation in the arena of discrete phase space is a partial difference equation. The energy eigenvalue problem for a three dimensional oscillator is exactly solved.Next, relativistic wave equations in the scenario of three dimensional discrete phase space and continuous time are explored. Specially, the partial finite difference-differential equation for a scalar field is investigated for the sake of simplicity. The exact relativistic invariance of the partial finite difference-differential version of the Klein-Gordon equation is rigorously proved. Moreover, it is shown that all nine important Green’s functions of the partial finite difference-differential wave equation for the scalar field are non-singular.In the appendix, a possible physical interpretation for the discrete orbits in the phase space as degenerate, string-like phase cells is provided in a mathematically rigorous way.

Jerry Goodisman