On Zeeman's collapsibility conjecture for non-standard polyhedra
We prove that if Zeeman's collapsibility conjecture holds for standard polyhedra, then it holds in general.
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arXiv subjects
Ivan Dynnikov
Publications and source records attributed to Ivan Dynnikov.
Rectangular diagrams of foliations
A concept of a rectangular diagram of a foliation in the three-sphere is introduced. It is shown that any co-orientable finite depth foliation in the complement of a link admits a presentation by a rectangular diagram compatible with the given rectangular diagram of the link.
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An algorithm for comparing Legendrian knots
We construct an algorithm to decide whether two given Legendrian or transverse links are equivalent. In general, the complexity of the algorithm is too high for practical implementation. However, in many cases, when the symmetry group of the link is small and explicitly known, the most time-consuming part of the algorithm can be bypassed, thus allowing one to compare many pairs of Legendrian and transverse links in practice.
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Features of the motion of ultracold atoms in quasiperiodic potentials
We consider here quasiperiodic potentials on the plane, which can serve as a "transitional link" between ordered (periodic) and chaotic (random) potentials. As can be shown, in almost any family of quasiperiodic potentials depending on a certain set of parameters, it is possible to distinguish a set (in the parameter space) where, according to a certain criterion, potentials with features of ordered potentials arise, and a set where we have potentials with features of random potentials. These sets complement each other in the complete parameter space, and each of them has its own specific structure. The difference between "ordered" and "chaotic" potentials will manifest itself, in particular, in the transport properties at different energies, which we consider here in relation to systems of ultracold atoms. It should be noted here that the transport properties of particles in the considered potentials can be accompanied by the phenomena of "partial integrability" inherent in two-dimensional Hamiltonian systems.
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Dynamical systems around the Rauzy gasket and their ergodic properties
At the beggining of the 80's, H.Masur and W.Veech started the study of generic properties of interval exchange transformations proving that almost every such transformation is uniquely ergodic. About the same time, S.Novikov's school and French mathematicians independently discovered very intriguing phenomena for classes of measured foliations on surfaces and respective IETs. For instance, minimality is exceptional in these families. A precise version of this statement is a conjecture by Novikov. The French and Russian constructions are very different ones. Nevertheless, in the most simple situation (surfaces of genus three with two singularities) it was recently observed that both foliations share the same type of properties. For instance, the space of minimal parameters is the same, called the Rauzy gasket. However, the precise connection between these two series of works was rather unclear. The aim of this paper is to prove that both theories describe in different languages the same objects. This text provides an explicit dictionary between both constructions.
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Rectangular diagrams of surfaces: the basic moves
In earlier papers we introduced a representation of isotopy classes of compact surfaces embedded in the three-sphere by so called rectangular diagrams. The formalism proved useful for comparing Legendrian knots. The aim of this paper is to prove a Reidemeister type theorem for rectangular diagrams of surfaces.
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Counting intersections of normal curves
A fast algorithm for counting intersections of two normal curves on a triangulated surface is proposed. It yields a convenient way for treating mapping class groups of punctured surfaces by presenting mapping classes by matrices, and the composition by an exotic matrix multiplication. An efficient solution of the word problem for mapping class groups of punctured surfaces is proposed, with efficiency understood in a more restrictive way than the most common one.
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Multiflypes of rectangular diagrams of links
We introduce a new very large family of transformations of rectangular diagrams of links that preserve the isotopy class of the link. We provide an example when two diagrams of the same complexity are related by such a transformation and are not obtained from one another by any sequence of `simpler' moves not increasing the complexity of the diagram along the way.
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Transverse-Legendrian links
In recent joint works of the present author with M.Prasolov and V.Shastin a new technique for distinguishing Legendrian knots has been developed. In this paper the technique is extended further to provide a tool for distinguishing transverse knots. It is shown that the equivalence problem for transverse knots with trivial orientation-preserving symmetry group is algorithmically solvable. In a future paper the triviality condition for the orientation-preserving symmetry group will be dropped.
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Classification of Legendrian knots of topological type $7_6$ with maximal Thurston--Bennequin number
We classify Legendrian knots of topological type $7_6$ having maximal Thurston--Bennequin number confirming the corresponding conjectures of Chongchitmate--Ng.
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Distinguishing Legendrian knots with trivial orientation-preserving symmetry group
In a recent work of I.\,Dynnikov and M.\,Prasolov a new method of comparing Legendrian knots is proposed. In general, to apply the method requires a lot of technical work. In particular, one needs to search all rectangular diagrams of surfaces realizing certain dividing configurations. In this paper, it is shown that, in the case when the orientation-preserving symmetry group of the knot is trivial, this exhaustive search is not needed, which simplifies the procedure considerably. This allows one to distinguish Legendrian knots in certain cases when the computation of the known algebraic invariants is infeasible or is not informative. In particular, it is disproved here that when~$A\subset\mathbb R^3$ is an annulus tangent to the standard contact structure along~$\partial A$, then the two components of~$\partial A$ are always equivalent Legendrian knots. A candidate counterexample was proposed recently by I.\,Dynnikov and M.\,Prasolov, but the proof of the fact that the two components of~$\partial A$ are not Legendrian equivalent was not given. Now this work is accomplished. It is also shown here that the problem of comparing two Legendrian knots having the same topological type is algorithmically solvable provided that the orientation-preserving symmetry group of these knots is trivial.
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Rectangular diagrams of surfaces: distinguishing Legendrian knots
In an earlier paper we introduced rectangular diagrams of surfaces and showed that any isotopy class of a surface in the three-sphere can be presented by a rectangular diagram. Here we study transformations of those diagrams and introduce moves that allow transition between diagrams representing isotopic surfaces. We also introduce more general combinatorial objects called mirror diagrams and various moves for them that can be used to transform presentations of isotopic surfaces to each other. The moves can be divided into two types so that, vaguely speaking, type~I moves commute with type~II ones. This commutation is the matter of the main technical result of the paper. We use it as well as a relation of the moves to Giroux's convex surfaces to propose a new method for distinguishing Legendrian knots. We apply this method to show that two Legendrian knots having topological type $6_2$ are not equivalent. More applications of the method will be a subject of subsequent papers.
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Minimality of interval exchange transformations with restrictions
It is known since 40 years old paper by M. Keane that minimality is a generic (i.e. holding with probability one) property of an irreducible interval exchange transformation. If one puts some integral linear restrictions on the parameters of the interval exchange transformation, then minimality may become an "exotic" property. We conjecture in this paper that this occurs if and only if the linear restrictions contain a Lagrangian subspace of the first homology of the suspension surface. We partially prove it in the "only if" direction and provide a series of examples to support the converse one. We show that the unique ergodicity remains a generic property if the restrictions on the parameters do not contain a Lagrangian subspace (this result is due to Barak Weiss).
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Rectangular diagrams of surfaces: representability
We introduce a simple combinatorial way, which we call a rectangular diagram of a surface, to represent a surface in the three-sphere. It has a particularly nice relation to the standard contact structure on $\mathbb S^3$ and to rectangular diagrams of links. By using rectangular diagrams of surfaces we are going, in particular, to develop a method to distinguish Legendrian knots. This requires a lot of technical work of which the present paper addresses only the first basic question: which isotopy classes of surfaces can be represented by a rectangular diagram. Vaguely speaking the answer is this: there is no restriction on the isotopy class of the surface, but there is a restriction on the rectangular diagram of the boundary link that can arise from the presentation of the surface. The result extends to Giroux's convex surfaces for which this restriction on the boundary has a natural meaning. In a subsequent paper we are going to consider transformations of rectangular diagrams of surfaces and to study their properties. By using the formalism of rectangular diagrams of surfaces we also produce here an annulus in $\mathbb S^3$ that we expect to be a counterexample to the following conjecture: if two Legendrian knots cobound an annulus and have zero Thurston--Bennequin numbers relative to this annulus, then they are Legendrian isotopic.
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Symmetric band complexes of thin type and chaotic sections which are not quite chaotic
In a recent paper we constructed a family of foliated 2-complexes of thin type whose typical leaves have two topological ends. Here we present simpler examples of such complexes that are, in addition, symmetric with respect to an involution and have the smallest possible rank. This allows for constructing a 3-periodic surface in the three-space with a plane direction such that the surface has a central symmetry, and the plane sections of the chosen direction are chaotic and consist of infinitely many connected components. Moreover, typical connected components of the sections have an asymptotic direction, which is due to the fact that the corresponding foliation on the surface in the 3-torus is not uniquely ergodic.
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On typical leaves of a measured foliated 2-complex of thin type
It is known that all but finitely many leaves of a measured foliated 2-complex of thin type are quasi-isometric to an infinite tree with at most two topological ends. We show that if the foliation is cooriented, and the associated R-tree is self-similar, then a typical leaf has exactly one topological end. We also construct the first example of a foliated 2-complex of thin type whose typical leaf has exactly two topological ends. `Typical' means that the property holds with probability one in a natural sense.
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Bypasses for rectangular diagrams. Proof of Jones' conjecture and related questions
In the present paper a criteria for a rectangular diagram to admit a simplification is given in terms of Legendrian knots. It is shown that there are two types of simplifications which are mutually independent in a sense. A new proof of the monotonic simplification theorem for the unknot is given. It is shown that a minimal rectangular diagram maximizes the Thurston--Bennequin number for the corresponding Legendrian links. Jones' conjecture about the invariance of the algebraic number of intersections of a minimal braid representing a fixed link type is proved.
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Arc-presentations of links. Monotonic simplification
We prove that any arc-presentation of the unknot admits a monotonic simplification by elementary moves; this yields a simple algorithm for recognizing the unknot. We obtain similar results for split links and composite links.
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