Symmetries and Integrability of Difference Equations

A special issue of Symmetry (ISSN 2073-8994). This special issue belongs to the section "Mathematics".

Deadline for manuscript submissions: closed (31 July 2019) | Viewed by 4478

Special Issue Editors


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Guest Editor
Istituto Nazionale di Fisica Nucleare, Sezione Roma Tre,Via della Vasca Navale, 84, 00146 Roma, Italy
Interests: mathematical physics; integrable nonlinear systems; theories of groups and symmetries

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Guest Editor
School of Mathematics and Statistics, University of Sydney, Sydney, Australia
Interests: continuous and discrete integrable systems; algebraic entropy for quad-equations and for differential-difference equations; higher-order maps

Special Issue Information

Dear Colleagues,

The concept of integrability was introduced in classical mechanics in the 19th century for finite dimensional continuous Hamiltonian systems. It was extended to certain classes of nonlinear differential equations in the second half of the 20th century with the discovery of the inverse scattering transform and the birth of soliton theory. Additionally at the end of the 19th century, Lie group theory was invented as a powerful tool for obtaining exact analytical solutions of large classes of differential equations. Together, Lie group theory and integrability theory in its most general sense provide the main tools for solving nonlinear differential equations. Like differential equations, difference equations play an important role in physics and other sciences. They occur very naturally in the description of phenomena that are genuinely discrete. Indeed, they may actually be more fundamental than differential equations if space-time is actually discrete at very short distances. On the other hand, even when treating continuous phenomena described by differential equations it is very often necessary to resort to numerical methods. This involves a discretization of the differential equation, i.e., a replacement of the differential equation by a difference one. Given the well-developed and understood techniques of symmetry and integrability for differential equations a natural question to ask is whether it is possible to develop similar techniques for difference equations. The aim is, on one hand, to obtain powerful methods for solving integrable difference equations and to establish practical integrability criteria, telling us when the methods are applicable. On the other hand, Lie group methods can be adapted to solve difference equations analytically. Finally, integrability and symmetry methods can be combined with numerical methods to obtain improved numerical solutions of differential equations.

Prof. Decio Levi
Dr. Giorgio Gubbiotti
Guest Editors

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Keywords

  • Discrete, continuous and ultra-discrete Painlevé equations
  • Orthogonal polynomials, special functions and their relation to discrete integrable systems
  • Integrability criteria for single and multivariable difference equations and differential difference equations
  • Discrete differential geometry
  • Discrete integrable systems and isomonodromy transformations
  • Yang-Baxter maps and quantum discrete integrable systems
  • Continuous symmetries of discrete equations
  • Structure preserving dis-cretization of differential equations and numerical methods
  • Cluster algebras and discrete integrable systems
  • Dynamics on graphs and combinatorics
  • Difference Galois theory
  • Lattices and Symmetries in Physical Applications

Published Papers (2 papers)

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Research

11 pages, 758 KiB  
Article
Hirota Difference Equation and Darboux System: Mutual Symmetry
by Andrei Pogrebkov
Symmetry 2019, 11(3), 436; https://doi.org/10.3390/sym11030436 - 25 Mar 2019
Cited by 2 | Viewed by 2060
Abstract
We considered the relation between two famous integrable equations: The Hirota difference equation (HDE) and the Darboux system that describes conjugate curvilinear systems of coordinates in R 3 . We demonstrated that specific properties of solutions of the HDE with respect to independent [...] Read more.
We considered the relation between two famous integrable equations: The Hirota difference equation (HDE) and the Darboux system that describes conjugate curvilinear systems of coordinates in R 3 . We demonstrated that specific properties of solutions of the HDE with respect to independent variables enabled introduction of an infinite set of discrete symmetries. We showed that degeneracy of the HDE with respect to parameters of these discrete symmetries led to the introduction of continuous symmetries by means of a specific limiting procedure. This enabled consideration of these symmetries on equal terms with the original HDE independent variables. In particular, the Darboux system appeared as an integrable equation where continuous symmetries of the HDE served as independent variables. We considered some cases of intermediate choice of independent variables, as well as the relation of these results with direct and inverse problems. Full article
(This article belongs to the Special Issue Symmetries and Integrability of Difference Equations)
24 pages, 421 KiB  
Article
Algebraic Entropy of a Class of Five-Point Differential-Difference Equations
by Giorgio Gubbiotti
Symmetry 2019, 11(3), 432; https://doi.org/10.3390/sym11030432 - 22 Mar 2019
Cited by 3 | Viewed by 2013
Abstract
We compute the algebraic entropy of a class of integrable Volterra-like five-point differential-difference equations recently classified using the generalised symmetry method. We show that, when applicable, the results of the algebraic entropy agrees with the result of the generalised symmetry method, as all [...] Read more.
We compute the algebraic entropy of a class of integrable Volterra-like five-point differential-difference equations recently classified using the generalised symmetry method. We show that, when applicable, the results of the algebraic entropy agrees with the result of the generalised symmetry method, as all the equations in this class have vanishing entropy. Full article
(This article belongs to the Special Issue Symmetries and Integrability of Difference Equations)
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