Darboux transformations for linear operators on regular two dimensional lattices are reviewed. The six point scheme is considered as the master linear problem, whose various specifications, reductions, and their sublattice combinations lead to other linear operators together with the corresponding Darboux transformations. The second part of the review deals with multidimensional aspects of (bas...

Abstract Isothermic surfaces are which allow a conformal curvature line parametrisation. They form an integrable system, and Darboux transforms of isothermic obey Bianchi permutability: for two distinct spectral parameters, the corresponding have common transform can be computed algebraically. In this paper, we discuss two-step with same parameter, show that these obtained by Sym-type construct...

We study differential-difference equation of the form d dx t(n+ 1, x) = f(t(n, x), t(n + 1, x), d dx t(n, x)) with unknown t(n, x) depending on continuous and discrete variables x and n. Equation of such kind is called Darboux integrable, if there exist two functions F and I of a finite number of arguments x, {t(n ± k, x)}k=−∞, { d dxk t(n, x) }∞ k=1 , such that DxF = 0 and DI = I, where Dx is ...

We analyze a certain class of integral equations associated with Marchenko equations and Gel’fand-Levitan equations. Such integral equations arise through a Fourier transformation on various ordinary differential equations involving a spectral parameter. When the integral operator is perturbed by a finite-rank perturbation, we explicitly evaluate the change in the solution in terms of the unper...

In this paper, we study the special tube surfaces generated by rectifying curves with respect to Darboux frame in terms of geodesic curvature, normal curvature and torsion Galilean 3-space. During establish some definite results geodesics on specific help Clairaut’s theorem detail compute Gaussian mean frame. After that, considering conditions curvatures surface, give theorems for $v$-parameter...

In this paper we consider the problems connected with the continuity of Darboux transformations and the monotonicity of the restrictions of these transformations. We show that it becomes possible to give answers to many questions concerning these problems if our considerations are confined to the family of c-functions which is defined in the paper. In paper [DG] (1875), the first example of a d...

To decide when a differential system is integrable or not is one of the hardest problems of the theory of differential equations. The existence and the calculus of first integrals are in general a difficult problem. Many techniques have been applied in order to construct first integrals, such as Lie symmetries, Noether symmetries, the Painlevé analysis, the use of Lax pairs, the Darboux method,...

Unifying hierarchies of integrable equations are discussed. They are constructed via generalized Hirota identity. It is shown that the Combescure transformations, known for a long time for the Darboux system and having a simple geometrical meaning, are in fact the symmetry transformations of generalized integrable hierarchies. Generalized equation written in terms of invariants of Combescure tr...

The technique of Darboux transformation is applied to nonlocal partner of two–dimensional periodic A n−1 Toda lattice. This system is shown to admit a representation as the compatibility conditions of direct and dual overdetermined linear systems with quantized spectral parameter. The generalization of the Darboux transformation technique on linear equations of such a kind is given. The solutio...

A version of the iterated Bäcklund-Darboux transformation, where Darboux matrix takes a form of the transfer matrix function from the system theory, is constructed for the discrete canonical system and Non-Abelian Toda lattice. Results on the transformations of the Weyl functions, insertion of the eigenvalues, and construction of the bound states are obtained. A wide class of the explicit solut...