Discrete Derivative Nonlinear Schrödinger Equations

We consider novel discrete derivative nonlinear Schrödinger equations (ddNLSs). Taking the continuum derivative nonlinear Schrödinger equation (dNLS), we use for the discretisation of the derivative the forward, backward, and central difference schemes, respectively, and term the corresponding equat...

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Main Authors: Dirk Hennig, Jesús Cuevas-Maraver
Format: Article
Language:English
Published: MDPI AG 2024-12-01
Series:Mathematics
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Online Access:https://www.mdpi.com/2227-7390/13/1/105
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author Dirk Hennig
Jesús Cuevas-Maraver
author_facet Dirk Hennig
Jesús Cuevas-Maraver
author_sort Dirk Hennig
collection DOAJ
description We consider novel discrete derivative nonlinear Schrödinger equations (ddNLSs). Taking the continuum derivative nonlinear Schrödinger equation (dNLS), we use for the discretisation of the derivative the forward, backward, and central difference schemes, respectively, and term the corresponding equations forward, backward, and central ddNLSs. We show that in contrast to the dNLS, which is completely integrable and supports soliton solutions, the forward and backward ddNLSs can be either dissipative or expansive. As a consequence, solutions of the forward and backward ddNLSs behave drastically differently compared to those of the (integrable) dNLS. For the dissipative forward ddNLS, all solutions decay asymptotically to zero, whereas for the expansive forward ddNLS all solutions grow exponentially in time, features that are not present in the dynamics of the (integrable) dNLS. In comparison, the central ddNLS is characterized by conservative dynamics. Remarkably, for the central ddNLS the total momentum is conserved, allowing the existence of solitary travelling wave (TW) solutions. In fact, we prove the existence of solitary TWs, facilitating Schauder’s fixed-point theorem. For the damped forward expansive ddNLS we demonstrate that there exists such a balance of dissipation so that solitary stationary modes exist.
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spelling doaj-art-460f06ec085e4f818ca9d58bf40173ad2025-01-10T13:18:16ZengMDPI AGMathematics2227-73902024-12-0113110510.3390/math13010105Discrete Derivative Nonlinear Schrödinger EquationsDirk Hennig0Jesús Cuevas-Maraver1Department of Mathematics, University of Thessaly, 35100 Lamia, GreeceGrupo de Física No Lineal, Departamento de Física Aplicada I, Universidad de Sevilla, Escuela Politécnica Superior, C/Virgen de África, 7, 41011 Sevilla, SpainWe consider novel discrete derivative nonlinear Schrödinger equations (ddNLSs). Taking the continuum derivative nonlinear Schrödinger equation (dNLS), we use for the discretisation of the derivative the forward, backward, and central difference schemes, respectively, and term the corresponding equations forward, backward, and central ddNLSs. We show that in contrast to the dNLS, which is completely integrable and supports soliton solutions, the forward and backward ddNLSs can be either dissipative or expansive. As a consequence, solutions of the forward and backward ddNLSs behave drastically differently compared to those of the (integrable) dNLS. For the dissipative forward ddNLS, all solutions decay asymptotically to zero, whereas for the expansive forward ddNLS all solutions grow exponentially in time, features that are not present in the dynamics of the (integrable) dNLS. In comparison, the central ddNLS is characterized by conservative dynamics. Remarkably, for the central ddNLS the total momentum is conserved, allowing the existence of solitary travelling wave (TW) solutions. In fact, we prove the existence of solitary TWs, facilitating Schauder’s fixed-point theorem. For the damped forward expansive ddNLS we demonstrate that there exists such a balance of dissipation so that solitary stationary modes exist.https://www.mdpi.com/2227-7390/13/1/105discrete derivative nonlinear Schrödinger equationssolitonsasymptotic behaviour of solutionstravelling solitary waves
spellingShingle Dirk Hennig
Jesús Cuevas-Maraver
Discrete Derivative Nonlinear Schrödinger Equations
Mathematics
discrete derivative nonlinear Schrödinger equations
solitons
asymptotic behaviour of solutions
travelling solitary waves
title Discrete Derivative Nonlinear Schrödinger Equations
title_full Discrete Derivative Nonlinear Schrödinger Equations
title_fullStr Discrete Derivative Nonlinear Schrödinger Equations
title_full_unstemmed Discrete Derivative Nonlinear Schrödinger Equations
title_short Discrete Derivative Nonlinear Schrödinger Equations
title_sort discrete derivative nonlinear schrodinger equations
topic discrete derivative nonlinear Schrödinger equations
solitons
asymptotic behaviour of solutions
travelling solitary waves
url https://www.mdpi.com/2227-7390/13/1/105
work_keys_str_mv AT dirkhennig discretederivativenonlinearschrodingerequations
AT jesuscuevasmaraver discretederivativenonlinearschrodingerequations