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In this paper, we provide the necessary and sufficient conditions for the connected sum of knots in $S^3$ to be Legendrian simple.

Geometric Topology · Mathematics 2021-01-11 Byung Hee An

This is the third installment in a series of papers on the subject of derived contact structures. In this paper, we formally introduce the notion of a Legendrian structure in the derived context and provide natural constructions. We then…

Symplectic Geometry · Mathematics 2025-07-01 Kadri İlker Berktav

For any Legendrian knot or link in $\mathbb{R}^3$, we construct an $L_\infty$ algebra that can be viewed as an extension of the Chekanov-Eliashberg differential graded algebra. The $L_\infty$ structure incorporates information from rational…

Symplectic Geometry · Mathematics 2025-07-21 Lenhard Ng

In this paper, we determine the group of contact transformations modulo contact isotopies for Legendrian circle bundles over closed surfaces of nonpositive Euler characteristic. These results extend and correct those presented by the first…

Geometric Topology · Mathematics 2019-02-20 Emmanuel Giroux , Patrick Massot

Partial connections are (singular) differential systems generalizing classical connections on principal bundles, yielding analogous decompositions for manifolds with nonfree group actions. Connection forms are interpreted as maps…

Differential Geometry · Mathematics 2007-05-23 Debra Lewis , Nilima Nigam , Peter Olver

We define and study multiplicative connections in the tangent bundle of a Lie groupoid. Multiplicative connections are linear connections satisfying an appropriate compatibility with the groupoid structure. Our definition is natural in the…

Differential Geometry · Mathematics 2021-10-12 Fabrizio Pugliese , Giovanni Sparano , Luca Vitagliano

We define an invariant of Legendrian links in the double-point enhanced grid homology of a link, and prove that it obstructs decomposable Lagrangian cobordisms in the symplectization of the standard contact structure on $\mathbb R^3$.

Geometric Topology · Mathematics 2025-05-13 Ashton Lewis , Zachary Ojakli , Ina Petkova , Benjamin Shapiro

The description of point defects in chiral liquid crystals via topological methods requires the introduction of singular contact structures, a generalisation of regular contact structures where the plane field may have singularities at…

Symplectic Geometry · Mathematics 2019-11-25 Joseph Pollard , Gareth P. Alexander

This is an introduction to Legendrian contact homology and the Chekanov-Eliashberg differential graded algebra, with a focus on the setting of Legendrian knots in $\mathbb{R}^3$. This is the published version of the paper, but with a…

Symplectic Geometry · Mathematics 2023-04-21 John B. Etnyre , Lenhard L. Ng

The set N of all null geodesics of a globally hyperbolic (d+1)-dimensional spacetime (M,g) is naturally a smooth (2d-1)-dimensional contact manifold. The sky of an event is the subset of N defined by all null geodesics through that event,…

General Relativity and Quantum Cosmology · Physics 2012-07-15 Jose Natario , Paul Tod

We present new families of examples of non-simple prime Legendrian and transversal knots in tight Lens spaces, which demonstrate that the botany of Legendrians in Lens space is rich. In fact, there are more non-isotopic Legendrians that are…

Geometric Topology · Mathematics 2025-12-29 Ipsita Datta , Tanushree Shah

We present classification results for exceptional Legendrian realisations of torus knots. These are the first results of that kind for non-trivial topological knot types. Enumeration results of Ding-Li-Zhang concerning tight contact…

Symplectic Geometry · Mathematics 2021-01-05 Hansjörg Geiges , Sinem Onaran

We present two different constructions of invariants for Legendrian knots in the standard contact space $\R^3$. These invariants are defined combinatorially, in terms of certain planar projections, and are useful in distinguishing…

Geometric Topology · Mathematics 2007-05-23 Yuri Chekanov

In this paper we show that the singular locus of a Legendrian foliation as defined in [Hua13] is a compact submanifold whose connected components are of codimension at most two. As a consequence, given any closed $(n+1)$-dimensional…

Symplectic Geometry · Mathematics 2014-11-24 Yang Huang

We classify Legendrian torus knots and figure eight knots in the tight contact structure on the 3-sphere up to Legendrian isotopy. As a corollary to this we also obtain the classification of transversal torus knots and figure eight knots up…

Geometric Topology · Mathematics 2007-05-23 John B. Etnyre , Ko Honda

The Thurston-Bennequin invariant provides one notion of self-linking for any homologically-trivial Legendrian curve in a contact three-manifold. Here we discuss related analytic notions of self-linking for Legendrian knots in Euclidean…

Symplectic Geometry · Mathematics 2018-08-22 Chris Beasley , Brendan McLellan , Ruoran Zhang

The aim of this paper is to define certain algebraic structures coming from generalized Reidemeister moves of singular knot theory. We give examples, show that the set of colorings by these algebraic structures is an invariant of singular…

Geometric Topology · Mathematics 2018-06-21 Indu R. U. Churchill , M. Elhamdadi , M. Hajij , Sam Nelson

In this note, we first classify all topological torus knots lying on the Heegaard torus in lens spaces, and then we study Legendrian representatives of these knots. We classify oriented positive Legendrian torus knots in the universally…

Geometric Topology · Mathematics 2017-10-02 Sinem Onaran

Many interesting spaces --- including all positroid strata and wild character varieties --- are moduli of constructible sheaves on a surface with microsupport in a Legendrian link. We show that the existence of cluster structures on these…

Symplectic Geometry · Mathematics 2019-12-19 Vivek Shende , David Treumann , Harold Williams , Eric Zaslow

We construct new unbounded invariant distances on the universal cover of certain Legendrian isotopy classes. This is the first instance where unboundedness of an invariant distance is obtained without assuming the existence of a positive…

Symplectic Geometry · Mathematics 2025-07-28 Pierre-Alexandre Arlove