2,875 research outputs found
Frobenius manifolds from regular classical -algebras
We obtain polynomial Frobenius manifolds from classical -algebras
associated to regular nilpotent elements in simple Lie algebras using the
related opposite Cartan subalgebras
Frobenius Manifolds and Central Invariants for the Drinfeld - Sokolov Bihamiltonian Structures
The Drinfeld - Sokolov construction associates a hierarchy of bihamiltonian
integrable systems with every untwisted affine Lie algebra. We compute the
complete set of invariants of the related bihamiltonian structures with respect
to the group of Miura type transformations.Comment: 73 pages, no figure
Virasoro Symmetries of the Extended Toda Hierarchy
We prove that the extended Toda hierarchy of \cite{CDZ} admits nonabelian Lie
algebra of infinitesimal symmetries isomorphic to the half of the Virasoro
algebra. The generators , of the Lie algebra act by linear
differential operators onto the tau function of the hierarchy. We also prove
that the tau function of a generic solution to the extended Toda hierarchy is
annihilated by a combination of the Virasoro operators and the flows of the
hierarchy. As an application we show that the validity of the Virasoro
constraints for the Gromov-Witten invariants and their descendents
implies that their generating function is the logarithm of a particular tau
function of the extended Toda hierarchy.Comment: A remark at the end of Section 5 is added; more detailed explanations
in Appendix; references adde
The twistor theory of Whitham hierarchy
We have established a 1-1 correspondence between a solution of the universal
Whitham hierarchy and a twistor space. The twistor space consists of a complex
surface and a family of complex curves together with a meromorphic 2-form. The
solution of the Whitham hierarchy is given by deforming the curve in the
surface. By treating the family of algebraic curves in as a
twistor space, we were able to express the deformations of the isomonodromic
spectral curve in terms of the deformations generated by the Whitham hierarchy.Comment: 27 page
On universality of critical behaviour in Hamiltonian PDEs
Our main goal is the comparative study of singularities of solutions to the
systems of first order quasilinear PDEs and their perturbations containing
higher derivatives. The study is focused on the subclass of Hamiltonian PDEs
with one spatial dimension. For the systems of order one or two we describe the
local structure of singularities of a generic solution to the unperturbed
system near the point of "gradient catastrophe" in terms of standard objects of
the classical singularity theory; we argue that their perturbed companions must
be given by certain special solutions of Painleve' equations and their
generalizations.Comment: 59 pages, 2 figures. Amer. Math. Soc. Transl., to appea
From Darboux-Egorov system to bi-flat -manifolds
Motivated by the theory of integrable PDEs of hydrodynamic type and by the
generalization of Dubrovin's duality in the framework of -manifolds due to
Manin [22], we consider a special class of -manifolds, called bi-flat
-manifolds. A bi-flat -manifold is given by the following data , where is an -manifold, is
the identity of the product , is a flat connection compatible
with and satisfying , while is an eventual identity
giving rise to the dual product *, and is a flat connection
compatible with * and satisfying . Moreover, the two connections
and are required to be hydrodynamically almost equivalent
in the sense specified in [2].
First we show that, similarly to the way in which Frobenius manifolds are
constructed starting from Darboux-Egorov systems, also bi-flat -manifolds
can be built from solutions of suitably augmented Darboux-Egorov systems,
essentially dropping the requirement that the rotation coefficients are
symmetric.
Although any Frobenius manifold possesses automatically the structure of a
bi-flat -manifold, we show that the latter is a strictly larger class. In
particular we study in some detail bi-flat -manifolds in dimensions n=2, 3.
For instance, we show that in dimension 3 bi-flat -manifolds are
parametrized by solutions of a two parameters Painlev\'e VI equation, admitting
among its solutions hypergeometric functions. Finally we comment on some open
problems of wide scope related to bi-flat -manifolds.Comment: 32 pages, eliminated a remark at the end of proof of Theorem 6.
Flat pencils of metrics and Frobenius manifolds
This paper is based on the author's talk at 1997 Taniguchi Symposium
``Integrable Systems and Algebraic Geometry''. We consider an approach to the
theory of Frobenius manifolds based on the geometry of flat pencils of
contravariant metrics. It is shown that, under certain homogeneity assumptions,
these two objects are identical. The flat pencils of contravariant metrics on a
manifold appear naturally in the classification of bihamiltonian structures
of hydrodynamics type on the loop space . This elucidates the relations
between Frobenius manifolds and integrable hierarchies.Comment: 25 pages, no figures, plain Te
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