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# Elements of the theory of solitons

2022/2023
Учебный год
ENG
Обучение ведется на английском языке
6
Кредиты

#### Преподаватель

Спирова Светлана Николаевна

### Course Syllabus

#### Abstract

Solitons – structurally stable wave objects in nonlinear dynamical systems — were discovered in the 1970s in a series of basic nonlinear equations of physics; the class of soliton-like solutions of integrable and non-integrable equations continues to broaden. Solitons are essential or even dominant parts of wave solutions in practically important problems of physics (for example, the data transmission by optical pulses, internal waves and rogue waves in the ocean, non-destructive diagnostics of composite materials) and much beyond. The elaboration of the theory of solitons and of the theory of integrable systems has yielded the appearance and ongoing development of the corresponding mathematical techniques, and also broadening of the field of practical applications. The course will give an introduction to the theory of solitons – as a part of nonlinear dynamics. The distinctive features of these structures among nonlinear waves, the variety of their manifestations (solitons, envelope solitons, breathers) will be shown. The key elements of the Inverse Scattering Technique, and also the basic examples will be discussed. On the basis of multisoliton solutions, the features of the nonlinear wave interaction and focusing will be considered. Actual problems of the scientific research in the fields of nonlinear optics and hydrodynamics will be emphasized.

#### Learning Objectives

• familiarization with solutions of nonlinear partial differential equations of the soliton type, the study of their characteristic properties and typical dynamics, in contrast to linear and nonlinear dispersive waves
• formation of the basic knowledge and skills applied to the research of properties of soliton-type waves
• awareness of the Inverse Scattering Transform as a nonlinear spectral method for studying wave dynamics
• familiarization with actual scientific problems related to the dynamics of soliton-type waves

#### Expected Learning Outcomes

• Aware of the basic properties of the KdV equation, can derive the first integrals of the equation, familiar with the properties of the solitons and their collisions, have a broader view on the KdV-type integrable equations and their soliton-type solutions
• Aware of the basic properties of the NLS equation, of the exact solutions bright/gray/dark solutions and breathers, rogue waves, familiar with the concept of the complex amplitude.
• Aware of the main equations of the wave type, able to recognize nonlinear equations and linear equations with dispersion, can write the dispersion relation for a given linear equation with dispersion, can derive the soliton solution as the localized stationary solution
• Has general understanding of the Inverse Scattering Transform, its similarity and difference from the Fourier method, understands the relation between isolated solutions, discrete eigenspectrum of the associated scattering problem and reflectionless potentials.

#### Course Contents

• Wave equations: linear, nonlinear, with soliton solutions
• Korteweg-de Vries equation and its generalizations
• Nonlinear Schrödinger equation
• Nonlinear spectral analysis
• Generalization and repetition

#### Assessment Elements

• Home Works and Short Classworks
• Activity during the seminars
• Written examination

#### Interim Assessment

• 2022/2023 4th module
0.2 * Home Works and Short Classworks + 0.4 * Written examination + 0.1 * Activity during the seminars

#### Recommended Core Bibliography

• Guo, B., Pang, X.-F., Wang, Y.-F., & Liu, N. (2018). Solitons. Berlin: De Gruyter. Retrieved from http://search.ebscohost.com/login.aspx?direct=true&site=eds-live&db=edsebk&AN=1746464
• Shilnikov L.P., Shilnikov A.L., Turaev D.V., Chua L.O. Methods Of Qualitative Theory In Nonlinear Dynamics (Part II). World Sci //Singapore, New Jersey, London, Hong Kong. – 2001.