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V. E. Adler

Publications and source records attributed to V. E. Adler.

45 records · Page 3Linked to original sources
arXiv2003

Q4

One of the most fascinating and technically demanding parts of the theory of two-dimensional integrable systems constitute the models with the spectral parameter on an elliptic curve, including Landau-Lifshitz and Krichever-Novikov equations, as well as elliptic Toda and Ruijsenaars-Toda lattices, elliptic Volterra lattice and Shabat-Yamilov lattice. We explain how all these models can be unified on the basis of a single equation Q4 on a quad-graph. This discrete model plays the role of the ``master equation'' in the (sl(2) part of) 2D integrability: most of other models in this area can be obtained from this one by certain limiting procedures. More precisely, discrete versions of all of the above mentioned models appear from Q4 imposed on a multi-dimensional cubic lattice. Zero curvature representations for all models appear as a byproduct of the general construction.

nlin.SI↗
arXiv2003

Geometry of Yang--Baxter maps: pencils of conics and quadrirational mappings

Birational Yang-Baxter maps (`set-theoretical solutions of the Yang-Baxter equation') are considered. A birational map $(x,y)\mapsto(u,v)$ is called quadrirational, if its graph is also a graph of a birational map $(x,v)\mapsto(u,y)$. We obtain a classification of quadrirational maps on $\CP^1\times\CP^1$, and show that all of them satisfy the Yang-Baxter equation. These maps possess a nice geometric interpretation in terms of linear pencil of conics, the Yang-Baxter property being interpreted as a new incidence theorem of the projective geometry of conics.

math.QA↗
arXiv2002

Classification of integrable equations on quad-graphs. The consistency approach

A classification of discrete integrable systems on quad-graphs, i.e. on surface cell decompositions with quadrilateral faces, is given. The notion of integrability laid in the basis of the classification is the three-dimensional consistency. This property yields, among other features, the existence of the discrete zero curvature with a spectral parameter. For all integrable systems of the obtained exhaustive list, the so called three-leg forms are found. This establishes Lagrangian and symplectic structures for these systems, and the connection to discrete systems of the Toda type on arbitrary graphs. Generalizations of these ideas to the three-dimensional integrable systems and to the quantum context are also discussed.

nlin.SI↗
arXiv2000

On the relation between multifield and multidimensional integrable equations

The new examples are found of the constraints which link the 1+2-dimensional and multifield integrable equations and lattices. The vector and matrix generalizations of the Nonlinear Schrödinger equation and the Ablowitz-Ladik lattice are considered among the other multifield models. It is demonstrated that using of the symmetries belonging to the hierarchies of these equations leads, in particular, to the KP equation and twodimensional analogs of the dressing chain, Toda lattice and dispersive long waves equations. In these examples the multifield equation and its symmetry have meaning of the Lax pair for the corresponding twodimensional equation under some compatible constraint between field variables and eigenfunctions.

nlin.SI↗
arXiv1999

Discrete analogues of the Liouville equation

The notion of Laplace invariants is transferred to the lattices and discrete equations which are difference analogs of hyperbolic PDE's with two independent variables. The sequence of Laplace invariants satisfy the discrete analog of twodimensional Toda lattice. The terminating of this sequence by zeroes is proved to be the necessary condition for existence of the integrals of the equation under consideration. The formulae are presented for the higher symmetries of the equations possessing integrals. The general theory is illustrated by examples of difference analogs of Liouville equation.

solv-int↗
arXiv1998

Legendre transformations on the triangular lattice

The main purpose of the paper is to demonstrate that condition of invariance with respect to the Legendre transformations allows effectively isolate the class of integrable difference equations on the triangular lattice, which can be considered as discrete analogues of relativistic Toda type lattices. Some of obtained equations are new, up to the author knowledge. As an example, one of them is studied in more details, in particular, its higher continuous symmetries and zero curvature representation are found.

solv-int↗
arXiv1995

Integrable boundary conditions for the Toda lattice

The problem of construction of the boundary conditions for the Toda lattice compatible with its higher symmetries is considered. It is demonstrated that this problem is reduced to finding of the differential constraints consistent with the ZS-AKNS hierarchy. A method of their construction is offered based on the Bäcklund transformations. It is shown that the generalized Toda lattices corresponding to the non-exceptional Lie algebras of finite growth can be obtained by imposing one of the four simplest integrable boundary conditions on the both ends of the lattice. This fact allows, in particular, to solve the problem of reduction of the series $A$ Toda lattices into the series $D$ ones. Deformations of the found boundary conditions are presented which leads to the Painlevé type equations. Key words: Toda lattice, boundary conditions, integrability, Bäcklund transformation, Lie algebras, Painlevé equations

solv-int↗
arXiv1994

Integrable deformations of a polygon

The new integrable mapping with a simple geometric interpretation is presented. This mapping arise from the nonlinear superposition principle for the Bäcklund transformations of some vector evolution equation.

solv-int↗