309 research outputs found

    On Negative Order KdV Equations

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    In this paper, based on the regular KdV system, we study negative order KdV (NKdV) equations about their Hamiltonian structures, Lax pairs, infinitely many conservation laws, and explicit multi-soliton and multi-kink wave solutions thorough bilinear B\"{a}cklund transformations. The NKdV equations studied in our paper are differential and actually derived from the first member in the negative order KdV hierarchy. The NKdV equations are not only gauge-equivalent to the Camassa-Holm equation through some hodograph transformations, but also closely related to the Ermakov-Pinney systems, and the Kupershmidt deformation. The bi-Hamiltonian structures and a Darboux transformation of the NKdV equations are constructed with the aid of trace identity and their Lax pairs, respectively. The single and double kink wave and bell soliton solutions are given in an explicit formula through the Darboux transformation. The 1-kink wave solution is expressed in the form of tanhtanh while the 1-bell soliton is in the form of sechsech, and both forms are very standard. The collisions of 2-kink-wave and 2-bell-soliton solutions, are analyzed in details, and this singular interaction is a big difference from the regular KdV equation. Multi-dimensional binary Bell polynomials are employed to find bilinear formulation and B\"{a}cklund transformations, which produce NN-soliton solutions. A direct and unifying scheme is proposed for explicitly building up quasi-periodic wave solutions of the NKdV equations. Furthermore, the relations between quasi-periodic wave solutions and soliton solutions are clearly described. Finally, we show the quasi-periodic wave solution convergent to the soliton solution under some limit conditions.Comment: 61 pages, 4 figure

    Binary Bell polynomials approach to the integrability of nonisospectral and variable-coefficient nonlinear equations

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    Recently, Lembert, Gilson et al proposed a lucid and systematic approach to obtain bilinear B\"{a}cklund transformations and Lax pairs for constant-coefficient soliton equations based on the use of binary Bell polynomials. In this paper, we would like to further develop this method with new applications. We extend this method to systematically investigate complete integrability of nonisospectral and variable-coefficient equations. In addiction, a method is described for deriving infinite conservation laws of nonlinear evolution equations based on the use of binary Bell polynomials. All conserved density and flux are given by explicit recursion formulas. By taking variable-coefficient KdV and KP equations as illustrative examples, their bilinear formulism, bilinear B\"{a}cklund transformations, Lax pairs, Darboux covariant Lax pairs and conservation laws are obtained in a quick and natural manner. In conclusion, though the coefficient functions have influences on a variable-coefficient nonlinear equation, under certain constrains the equation turn out to be also completely integrable, which leads us to a canonical interpretation of their NN-soliton solutions in theory.Comment: 39 page

    Painlev\'e analysis for nonlinear partial differential equations

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    The Painlev\'e analysis introduced by Weiss, Tabor and Carnevale (WTC) in 1983 for nonlinear partial differential equations (PDE's) is an extension of the method initiated by Painlev\'e and Gambier at the beginning of this century for the classification of algebraic nonlinear differential equations (ODE's) without movable critical points. In these lectures we explain the WTC method in its invariant version introduced by Conte in 1989 and its application to solitonic equations in order to find algorithmically their associated B\"acklund transformation. A lot of remarkable properties are shared by these so-called ``integrable'' equations but they are generically no more valid for equations modelising physical phenomema. Belonging to this second class, some equations called ``partially integrable'' sometimes keep remnants of integrability. In that case, the singularity analysis may also be useful for building closed form analytic solutions, which necessarily % Conte agree with the singularity structure of the equations. We display the privileged role played by the Riccati equation and systems of Riccati equations which are linearisable, as well as the importance of the Weierstrass elliptic function, for building solitary waves or more elaborate solutions.Comment: 61 pages, no figure, standard Latex, to appear in The Painlev\'e property, one century later, ed. R. Conte, CRM series in mathematical physics (Springer--Verlag, Berlin, 1998) (Carg\`ese school, 3-22 June 1996

    Equivalence transformations in the study of integrability

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    We discuss how point transformations can be used for the study of integrability, in particular, for deriving classes of integrable variable-coefficient differential equations. The procedure of finding the equivalence groupoid of a class of differential equations is described and then specified for the case of evolution equations. A class of fifth-order variable-coefficient KdV-like equations is studied within the framework suggested.Comment: 14 pages; the version accepted to Physica Script

    Open problems for the superKdV equations

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    After a review of the basic results concerning the N=1,2N=1,2 supersymmetric extensions of the Korteweg-de Vries equation, with a pedagogical presentation of the superspace techniques, we discuss some basic open problems mainly in relation with the N=2 extensions.Comment: harvmac, 13 p. (b); talk presented at AARMS-CRM Workshop on Backlund and Darboux Transformations: The geometry of Soliton Theory. June 4-9, 1999 (Halifax, Nova Scotia

    Generalized Super Bell Polynomials with Applications to Superymmetric Equations

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    In this paper, we introduce a class of new generalized super Bell polynomials on a superspace, explore their properties, and show that they are a natural and effective tool to systematically investigate integrability of supersymmetric equations. The connections between the super Bell polynomials and super bilinear representation, bilinear B\"{a}cklund transformation, Lax pair and infinite conservation laws of supersymmetric equations are established. We take supersymmetric KdV equation and supersymmetric sine-Gordon equation to illustrate this procedure.Comment: 36 page

    On a method for constructing the Lax pairs for nonlinear integrable equations

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    We suggest a direct algorithm for searching the Lax pairs for nonlinear integrable equations. It is effective for both continuous and discrete models. The first operator of the Lax pair corresponding to a given nonlinear equation is found immediately, coinciding with the linearization of the considered nonlinear equation. The second one is obtained as an invariant manifold to the linearized equation. A surprisingly simple relation between the second operator of the Lax pair and the recursion operator is discussed: the recursion operator can immediately be found from the Lax pair. Examples considered in the article are convincing evidence that the found Lax pairs differ from the classical ones. The examples also show that the suggested objects are true Lax pairs which allow the construction of infinite series of conservation laws and hierarchies of higher symmetries. In the case of the hyperbolic type partial differential equation our algorithm is slightly modified; in order to construct the Lax pairs from the invariant manifolds we use the cutting off conditions for the corresponding infinite Laplace sequence. The efficiency of the method is illustrated by application to some equations given in the Svinolupov-Sokolov classification list for which the Lax pairs and the recursion operators have not been found earlier

    Discrete KP equation with self-consistent sources

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    We show that the discrete Kadomtsev-Petviashvili (KP) equation with sources obtained recently by the "source generalization" method can be incorporated into the squared eigenfunction symmetry extension procedure. Moreover, using the known correspondence between Darboux-type transformations and additional independent variables, we demonstrate that the equation with sources can be derived from Hirota's discrete KP equations but in a space of higher dimension. In this way we uncover the origin of the source terms as coming from multidimensional consistency of the Hirota system itself.Comment: 11 pages; one reference added, several typos or grammatical errors corrected (v2

    The method of Poisson pairs in the theory of nonlinear PDEs

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    The aim of these lectures is to show that the methods of classical Hamiltonian mechanics can be profitably used to solve certain classes of nonlinear partial differential equations. The prototype of these equations is the well-known Korteweg-de Vries (KdV) equation. In these lectures we touch the following subjects: i) The birth and the role of the method of Poisson pairs inside the theory of the KdV equation; ii) the theoretical basis of the method of Poisson pairs; iii) the Gel'fand-Zakharevich theory of integrable systems on bihamiltonian manifolds; iv) the Hamiltonian interpretation of the Sato picture of the KdV flows and of its linearization on an infinite-dimensional Grassmannian manifold. v)the reduction technique and its use to construct classes of solutions; iv) the role of the technique of separation of variables in the study of the reduced systems. vii) some relations intertwining the method of Poisson pairs with the method of Lax pairs.Comment: 55 pages, Latex with amsmath and amssymb. Lectures given by F. Magri at the 1999 CIME course ``Direct and Inverse Methods in Solving Nonlinear Evolution Equations '' Cetraro, (Italy) September 199

    Deriving conservation laws for ABS lattice equations from Lax pairs

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    In the paper we derive infinitely many conservation laws for the ABS lattice equations from their Lax pairs. These conservation laws can algebraically be expressed by means of some known polynomials. We also show that H1, H2, H3, Q1, Q2, Q3 and A1 equation in ABS list share a generic discrete Riccati equation.Comment: 16 page
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