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A. Shabat

Publications and source records attributed to A. Shabat.

5 recordsLinked to original sources
arXiv2005

Computable Integrability. Chapter 2: Riccati equation

In this Chapter, using Riccati equation as our main example, we tried to demonstrate at least some of the ideas and notions introduced in Chapter 1 - integrability in quadratures, conservation laws, etc. Regarding transformation group and singularities of solutions for RE, we constructed some equivalent forms of Riccati equation. We also compared three different approaches to the solutions of Riccati equation and its equivalent forms. The classical form of RE allowed us to construct easily asymptotic solutions represented by formal series. Linear equation of the second order turned out to be more convenient to describe finite-gap potentials for exact solitonic solutions which would be a much more complicated task for a RE itself while generalization of soliton-like potentials to finite-gap potentials demanded modified Schwarzian equation.

math-ph↗
arXiv2005

Computable Integrability. Chapter 5: Factorization of LPDOs

Different definitions of integrability, as a rule, use linearization of initial equation and/or expansion on some basic functions which are themselves solutions of some linear differential equation. Important fact here is that linearization of some differential equation is its simplification but not solving yet. For instance, in case of linear Schroedinger equation, we are not able to find its solutions explicitly but only to name them Jost functions and to exploit their useful properties (see previous Chapters). On the other hand, well-known fact is that for LODE with constant coefficients operator itself can always be factorized into first-order factors and thus the problem is reduced to the solving of a few first-order LODEs which are solvable in quadratures. In case of differential operators with variable coefficients factorization is not always possible but for the great number of operators BK-factorization gives factorization conditions explicitly which we are going to demonstrate in this Chapter. BK factorization is used to construct set of invariants for LPDO of arbitrary order; interconnections of these new invariants with classic Laplace invariants for second order hyperbolic LPDOs are discussed.

math-ph↗
arXiv2005

Elementary Darboux transformations and factorization

A general theorem on factorization of matrices with polynomial entries is proven and it is used to reduce polynomial Darboux matrices to linear ones. Some new examples of linear Darboux matrices are discussed.

nlin.SI↗
arXiv2003

A new class of linearizable equations

Using the symmetry approach, we find a class of integrable nonlinear PDEs with dispersion law $ω(k)=k^{\frac32}$. All these equations turn out to be linearizable by means of a differential parametrization.

nlin.SI↗