Cauchy Matrix Approach Research Articles

A discrete negative AKNS equation: generalized Cauchy matrix approach

Generalized Cauchy matrix approach is used to investigate a discrete negative Ablowitz–Kaup–Newell–Segur (AKNS) equation. Several kinds of solutions more than multi-soliton solutions to this equation are derived by solving determining equation set. Furthermore, applying an appropriate continuum limit we obtain a semidiscrete negative AKNS equation and after a second continuum limit we derive the nonlinear negative AKNS equation. The reductions to discrete, semi-discrete and continuous sine-Gordon equations are also discussed.

The Sylvester equation and integrable equations: I. The Korteweg-de Vries system and sine-Gordon equation

The paper is to reveal the direct links between the well known Sylvester equation in matrix theory and some integrable systems. Using the Sylvester equation KM + MK = r sT we introduce a scalar function S(i, j) = sT Kj (I + M)−1Kir which is defined as same as in discrete case. S(i, j) satisfy some recurrence relations which can be viewed as discrete equations and play indispensable roles in deriving continuous integrable equations. By imposing dispersion relations on r and s, we find the Korteweg-de Vries equation, modified Korteweg-de Vries equation, Schwarzian Korteweg-de Vries equation and sine-Gordon equation can be expressed by some discrete equations of S(i, j) defined on certain points. Some special matrices are used to solve the Sylvester equation and prove symmetry property S(i, j) = S(j,i). The solution M provides t function by t = ∣I + M∣. We hope our results can not only unify the Cauchy matrix approach in both continuous and discrete cases, but also bring more links for integrable systems and variety of areas where the Sylvester equation appears frequently.

Solutions to ABS Lattice Equations via Generalized Cauchy Matrix Approach

The usual Cauchy matrix approach starts from a known plain wave factor vector and known dressed Cauchy matrix . In this paper, we start from a determining matrix equation set with undetermined and . From the determining equation set we can build shift relations for some defined scalar functions and then derive lattice equations. The determining equation set admits more choices for and and in the paper we give explicit formulae for all possible and . As applications, we get more solutions than usual multisoliton solutions for many lattice equations including the lattice potential KdV equation, the lattice potential modified KdV equation, the lattice Schwarzian KdV equation, NQC equation, and some lattice equations in ABS list.

Generalized Cauchy matrix approach for lattice KP-type equations

In this paper we generalize Cauchy matrix approach to study the lattice KP-type equations, including lattice potential KP equation, lattice potential mKP equation, lattice Schwarzian KP equation and lattice KP-type NQC equation. By solving the condition equation set, we give explicit formulae for all possible r, ts and M. Consequently, we get more solutions than usual multi-soliton solutions for these lattice KP-type equations.

Multidimensional inverse scattering of integrable lattice equations

We present a discrete inverse scattering transform for all ABS equations excluding Q4. The nonlinear partial difference equations presented in the ABS hierarchy represent a comprehensive class of scalar affine-linear lattice equations which possess the multidimensional consistency property. Due to this property it is natural to consider these equations living in an N-dimensional lattice, where the solutions depend on N distinct independent variables and associated parameters. The direct scattering procedure, which is one-dimensional, is carried out along a staircase within this multidimensional lattice. The solutions obtained are dependent on all N lattice variables and parameters. We further show that the soliton solutions derived from the Cauchy matrix approach are exactly the solutions obtained from reflectionless potentials, and we give a short discussion on solutions of some previously known lattice equations, such as the lattice KdV equation.

Generalized Cauchy matrix approach for lattice Boussinesq-type equations

The authors generalize the Cauchy matrix approach to get exact solutions to the lattice Boussinesq-type equations: lattice Boussinesq equation, lattice modified Boussinesq equation and lattice Schwarzian Boussinesq equation. Some kinds of solutions including soliton solutions, Jordan block solutions and mixed solutions are obtained.

EXACT SOLUTIONS TO LATTICE BOUSSINESQ-TYPE EQUATIONS

In this paper several kinds of exact solutions to lattice Boussinesq-type equations are constructed by means of generalized Cauchy matrix approach, including soliton solutions and mixed solutions. The introduction of the general condition equation set yields that all solutions contain two kinds of plane-wave factors.

Soliton solutions for ABS lattice equations: I. Cauchy matrix approach

In recent years there have been new insights into the integrability of quadrilateral lattice equations, i.e. partial difference equations which are the natural discrete analogues of integrable partial differential equations in 1+1 dimensions. In the scalar (i.e. single-field) case, there now exist classification results by Adler, Bobenko and Suris (ABS) leading to some new examples in addition to the lattice equations ‘of KdV type’ that were known since the late 1970s and early 1980s. In this paper, we review the construction of soliton solutions for the KdV-type lattice equations and use those results to construct N-soliton solutions for all lattice equations in the ABS list except for the elliptic case of Q4, which is left to a separate treatment.