Simple elliptic singularities: A note on their g-function

This is a survey article about the study of the links of some complex hypersurface singularities in ℂ3 . We study the links of simple singularities, simple elliptic singularities and cusp singularities, and the canonical contact structures on them. It is known that each singularity link is diffeomorphic to a compact quotient of a 3-dimensional Lie group SU (2), Nil3 or Sol3 , respectively. Moreover, the canonical contact structure is equivalent to the contact structure invariant under the action of each Lie group. We show a new proof of this fact using the moment polytope of S5 . Our proof gives a new aspect to the relation between simple elliptic singularities and cusp singularities, and visualizes how the singularity links are embedded in S5 as codimension two contact submanifolds.

A simple elliptic singularity can be described in terms of a marginal deformation of an invertible polynomial. The choice of the polynomials and its marginal deformation are not unique. In this paper, following the earlier work of Krawitz-Shen and Milanov-Ruan, we investigate the global mirror symmetry phenomenon for simple elliptic singularities. We prove that the mirror symmetry for each family is governed by a certain system of hypergeometric equations. We conjecture that the Saito-Givental theory of the family at any special limit is mirror to either the Gromov-Witten theory of an elliptic orbifold projective line or the Fan-Jarvis-Ruan-Witten theory of an invertible polynomial, and the limits are classified by the Milnor number of the singularity and the j-invariant at the special limit. We prove the conjecture holds at all special limits of the Fermat polynomials and at the Gepner points in all other cases.

For a finitely generated group G, we study deformation spaces of metric G-trees, which are analogues of the Teichmuller spaces of surfaces for group actions on trees. Deformation spaces of metric G-trees generalize Culler-Vogtmann’s Outer space, the deformation space of free actions on trees, which has proven to be immensely useful in the study of Out(Fn), the outer automorphism group of the free group of rank n ≥ 2. Let D be a deformation space of metric G-trees. The group of positive real numbers R>0 acts on D by scaling the metrics on the trees and we define the projectivized deformation space as the quotient PD = D/R>0. The outer auto- morphism group Out(G) contains a certain subgroup OutD(G) that acts on D and PD by precomposing the G-actions on the trees. In Chapter 1, we present a complete argument that under certain assumptions the projectivized deformation space PD is a model for the classifying space of OutD(G) for a family of subgroups. In Chapter 2, we introduce an asymmetric pseudometric on PD that generalizes the asymmetric Lipschitz metric on Outer space and is an analogue of the Thurston metric on Teichmuller space. Making use of the Lipschitz metric on PD, we prove existence of train track representatives for irreducible automorphisms of virtually free groups and nonelementary generalized Baumslag-Solitar groups that contain no solvable Baumslag-Solitar group BS(1, n) with n ≥ 2. In Chapter 3, we define the higher holomorphs Aut(G, k), k ∈ N, which are “higher-pointed” variants of the automorphism group Aut(G). Following the construction of the spine of Outer space, we construct a family of simplicial complexes S(PD, k), k ∈ N on which certain subgroups AutD(G, k) ≤ Aut(G, k) act and we show that these complexes are always contractible.

G-Frobenius manifolds

Proof of a conjecture on the genus two free energy associated to the [formula omitted] singularity

We give a geometric proof of a formula, due to Segal and Wilson, which describes the order of vanishing of the Riemann theta function in the direction which corresponds to the direction of the tangent space of a Riemann surface at a marked point. While this formula appears in the work of Segal and Wilson as a by-product of some nontrivial constructions from the theory of integrable systems (loop groups, infinite-dimensional Grassmannians, tau functions, Schur polynomials, etc.) our proof only uses the classical theory of linear systems on Riemann surfaces.

This paper focuses on the relevance of a certain class of left-invariant Hamiltonians (affine-quadratic) on a reductive semi-simple Lie algebra g for the theory of integrable systems and the equations of applied mathematics.Any semi-simple Lie group G that contains a closed subgroup K is reductive, in the sense, that the orthogonal complement p in g of the Lie algebra k of K , relative to the Killing form, satisfies [k, p] p.This implies that K acts (by adjoint action) on p and therefore induces the semi-direct product p K .Consequently, g , as a vector space, carries two Lie algebra structures: semi-simple, and semi-direct.Hence, the dual g * carries two Poisson structures as well.Any affine-quadratic function H on g can be simultaneously viewed as a Hamiltonian for either Poisson structure.We will show that certain coadjoint orbits relative to the semi-direct action are the cotangent bundles of SO(n).This implies that the equations of an n -dimensional top can be represented on such coadjoint orbits.In this situation there is a canonical affine-quadratic Hamiltonian whose Hamiltonian equations on these coadjoint orbits coincide with the equations of the top.This implies that the integrable cases of the top correspond to the the integrable cases of the overseeing affine Hamiltonian.More generally, we will identify a subclass of affine-quadratic Hamiltonians, called isospectral, that provides new insights into the theory of integrable systems based on the contributions of S. V. Manakov, A. T. Fomenko, A. S. Mischenko and O. Bogoyavlensky listed in the references.

The classification of real singularities using Singular Part I: Splitting Lemma and simple singularities

We identify the canonical contact structure on the link of a simple elliptic or cusp singularity by drawing a Legendrian handlebody diagram of one of its Stein fillings. We also show that the canonical contact structure on the link of a numerically Gorenstein surface singularity is trivial considered as a real plane bundle.

In this paper we develop a general approach to dimer models analogous to Krichever’s scheme in the theory of integrable systems. We start with a Riemann surface and the simplest generic meromorphic functions on it and demonstrate how to obtain integrable dimer models. These are dimer models on doubly periodic bipartite graphs with quasi-periodic positive weights. Dimer models with periodic weights and Harnack curves are recovered as a special case. This generalization from Harnack curves to general M-curves leads to transparent algebro-geometric structures. In particular explicit formulas for the Ronkin function and surface tension as integrals of meromorphic differentials on M-curves are obtained. Furthermore we describe the variational principle for the height function in the quasi-periodic case. Based on Schottky uniformizations of Riemann surfaces we present concrete computational results including computing the weights and sampling dimer configurations with them. The computational results are in complete agreement with the theoretical predictions.

Haantjes algebras and diagonalization

A general scheme of construction of Drinfeldians and Yangians from quantum non-twisted affine Kac-Moody algebras is presented. Explicit description of Drinfeldians and Yangians for all Lie algebras of the classical series A, B, C, D is given in terms of a Chevalley basis. Rational and trigonometric deformations of a universal enveloping algebra U(g(u)) (g is a finite-dimensional complex simple Lie algebra) - Yangian Yη(g) and a quantum (q-deformed) affine algebraUq(g(u)) - are playing increasingly a role in the theory of integrable systems and the quantum field theory. For applications it is useful to know various realizations (or bases) of these deformations. Among various realizations the Chevalley basis plays a special role due to its compactness and simplicity. In the case of the quantum affine algebras the Chevalley basis was originally introduced in the defining relations while the Yangians were initially de- fined in terms of a finite Cartesian basis (the first Drinfeld realization (2)) as well as in terms of a special infinite basis (the second Drinfeld realization (3)). It was not clear whether does exist a Chevalley basis for the Yangians. Recently in (12, 13) it was shown that the Yangian can be realized in terms of Chevalley basis and, moreover, there was found a simple connection of this realization with the corresponding quantum affine algebra (also see (14, 15)). This connection allows to introduce a new Hopf algebra called Drinfeldian which depends on two deformation parameters q and η. The Drinfeldian Dqη(g) can be considered as quantization of U(g(u)) in the direction of a classical r-matrix which is a sum of simplest rational and trigonometric r-matrices. When the parameter q goes to 1 we obtain the Yangian Yη(g) in terms of the Chevalley basis. In this paper we remind once more the procedure of construction of the Drin- feldian Dqη(g) and the Yangian Yη(g) in terms of the Chevalley basis starting from

At present there can be no doubt to say that the quantum group theory has been one of the most important, modern and rapidly developing directions of mathematics and mathematical physics in the end of the twentieth century. Although initially (in the early 1980’s) the quantum group theory was formulated for solving problems in the theory of integrable systems and statistical physics, later the surprising connection of this theory with many branches of mathematics, and the theoretical and mathematical physics was discovered. Today the quantum group theory is connected with such mathematical fields as special functions (especially, with (q-orthogonal polynomials and basic hypergeometric series), the theory of difference and differential equations, combinatorial analysis and representation theory, matrix and operator algebras, noncommutative geometry, knot theory, topology, category theory and so on. From point of view of the mathematical physics there exists interconnection of the quantum group theory with the quantum inverse scattering method, conformai and quantum fields theory and so on. It is expected that the quantum groups will provide deeper understanding of concept of symmetry in physics.KeywordsQuantum GroupSimple RootBasic Hypergeometric SeriesReduction ChainGeneral Projection OperatorThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Pseudo differential operators and integrable systems in AXIOM

Exploring surfaces through methods from the theory of integrable systems: The Bonnet problem