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48 results for rack invariants

We study Coxeter racks over Zn\mathbb{Z}_n and the knot and link invariants they define. We exploit the module structure of these racks to enhance the rack counting invariants and give examples showing that these enhanced invariants are stronger than the unenhanced rack counting invariants.

2008-08-11abs ↗pdf ↗

Study rack invariants for links in lens space L(p,1)L(p,1).

problem Applying classical rack invariants to links in L(p,1)L(p,1).
method Presented augmented fundamental rack, applied counting rack invariants, included information about π1(L(p,1))π_{1}(L(p,1)) action.
result Counting rack invariants provide information about π1(L(p,1))π_{1}(L(p,1)) action on links in L(p,1)L(p,1).

A rack shadow is a set X with a rack action by a rack R, analogous to a vector space over a field. We use shadow colorings of classical link diagrams to define enhanced rack counting invariants and show that the enhanced invariants are stronger than unenhanced counting invariants.

2009-10-15abs ↗pdf ↗

We introduce a modified rack algebra Z[X] for racks X with finite rack rank N. We use representations of Z[X] into rings, known as rack modules, to define enhancements of the rack counting invariant for classical and virtual knots and links. We provide computations and examples to show that the new invariants are stric…

2010-07-31abs ↗pdf ↗

We define ambient isotopy invariants of oriented knots and links using the counting invariants of framed links defined by finite racks. These invariants reduce to the usual quandle counting invariant when the rack in question is a quandle. We are able to further enhance these counting invariants with 2-cocycles from th…

2008-07-31abs ↗pdf ↗

This paper characterizes extensions of augmented racks and constructs invariants for surfaces.

problem Characterizing extensions of augmented racks and constructing invariants for surfaces.
method Characterization of rack extensions through fibrant and additive cohomology, construction of invariants using cocycles.
result Characterization of extensions of augmented racks and construction of surface invariants.

We study rack polynomials and the link invariants they define. We show that constant action racks are classified by their generalized rack polynomials and show that nsatans^at^a-quandles are not classified by their generalized quandle polynomials. We use subrack polynomials to define enhanced rack counting invariants, gen…

2008-09-29abs ↗pdf ↗

A (t,s)-rack is a rack structure defined on a module over the ring Λ¨=Z[t±1,s]/(s2(1t)s)\ddotΛ=\mathbb{Z}[t^{\pm 1},s]/(s^2-(1-t)s). We identify necessary and sufficient conditions for two (t,s)(t,s)-racks to be isomorphic. We define enhancements of the rack counting invariant using the structure of (t,s)-racks and give some computations an…

2010-11-24abs ↗pdf ↗

Racks do not give us invariants of surface-knots in general. For example, if a surface-knot diagram has branch points (and a rack which we use satisfies some mild condition), then it admits no rack colorings. In this paper, we investigate rack colorings for surface-knot diagrams without branch points and prove that rac…

2014-06-13abs ↗pdf ↗

The homology and cohomology of quandles and racks are used in knot theory: given a finite quandle and a cocycle, we can construct a knot invariant. This is a quick introductory survey to the invariants of knots derived from quandles and racks.

2002-11-05abs ↗pdf ↗

The aim of this paper is to define a homology theory for racks with finite rank N and use it to define invariants of knots generalizing the CJKLS 2-cocycle invariants related to the invariants defined in [15]. For this purpose, we prove that N -degenerate chains form a sub-complex of the classical complex defining rack…

2010-07-21abs ↗pdf ↗

Link invariants defined from finite crossed modules and Reidemeister pairs.

problem Defining link invariants from finite categorical groups.
method Definition of tangle and framed tangle invariants using finite crossed modules and Reidemeister pairs.
result Includes all rack and quandle cohomology (framed) link invariants and the Eisermann invariant of knots.

A birack is an algebraic structure with axioms encoding the blackboard-framed Reidemeister moves, incorporating quandles, racks, strong biquandles and semiquandles as special cases. In this paper we extend the counting invariant for finite racks to the case of finite biracks. We introduce a family of biracks generalizi…

2010-02-19abs ↗pdf ↗

Analytic Lie rack structures on Leibniz algebras are characterized and rigid Lie algebras are identified.

problem Characterizing and identifying rigid Lie algebras with analytic Lie rack structures.
method Analytic Lie rack structures are defined and characterized using multilinear equations and cohomological interpretations.
result Simple Lie algebras are conjectured to be rigid as left Leibniz algebras.

We introduce augmented biracks and define a (co)homology theory associated to augmented biracks. The new homology theory extends the previously studied Yang-Baxter homology with a combinatorial formulation for the boundary map and specializes to NN-reduced rack homology when the birack is a rack. We introduce augmente…

2013-09-06abs ↗pdf ↗

New racks defined; properties of rack representations explored.

problem Characterizing and studying rack representations.
method Definition of finitely stable racks, characterization of Alexander quandles, study of twisted rack dynamical systems, construction of cross-products, representation theory of racks and quandles.
result Definition and properties of Pontryagin dual of racks.

A rack of order nn is a binary operation $\rack$ on a set XX of cardinality nn, such that right multiplication is an automorphism. More precisely, $(X,\rack)$ is a rack provided that the map $x\mapsto x\rack y$ is a bijection for all yXy\in X, and $(x\rack y)\rack z=(x\rack z)\rack (y\rack z)$ for all x,y,zXx,y,z\in X. …

2012-03-29abs ↗pdf ↗

We give a foundational account on topological racks and quandles. Specifically, we define the notions of ideals, kernels, units, and inner automorphism group in the context of topological racks. Further, we investigate topological rack modules and principal rack bundles. Central extensions of topological racks are then…

2015-05-30abs ↗pdf ↗

Paper constructs infinitely many pairs of Seifert surfaces for each link.

problem Constructing infinitely many pairs of Seifert surfaces for each link.
method Using a multiple group rack (MGR) to construct invariants and distinguishing surfaces using these invariants.
result Presented infinitely many pairs of Seifert surfaces for each link, satisfying specific conditions.

The theory of rack and quandle modules is developed - in particular a tensor product is defined, and shown to satisfy an appropriate adjointness condition. Notions of free rack and quandle modules are introduced, and used to define an enveloping object (the `rack algebra' or `wring') for a given rack or quandle. These …

2004-11-02abs ↗pdf ↗

Quandle homology was defined from rack homology as the quotient by a subcomplex corresponding to the idempotency, for invariance under the type I Reidemeister move. Similar subcomplexes have been considered for various identities of racks and moves on diagrams. We observe common aspects of these identities and subcompl…

2016-02-27abs ↗pdf ↗

Classifies good involutions in conjugation subquandles and racks.

problem Classifying quandles with good involutions for applications in surface-knot theory.
method Study of subquandles of conjugation quandles, including core quandles; analysis of good involutions of faithful racks.
result Sharp bounds on the number of good involutions of racks in these families.

The main result of this paper is a new classification theorem for links (smooth embeddings in codimension 2). The classifying space is the rack space (defined in [Trunks and classifying spaces, Applied Categorical Structures, 3 (1995) 321--356]) and the classifying bundle is the first James bundle (defined in "James bu…

2003-04-16abs ↗pdf ↗

Defines fundamental racks for braid spaces of complex reflection groups.

problem Understanding fundamental racks for braid spaces of complex reflection groups.
method Defines an augmented rack associated to the orbifold fundamental group.
result Yields representations of the orbifold fundamental group on the cohomology of the rack space.

The paper constructs Yang-Baxter solutions using categorical augmented racks.

problem Solutions to the Yang-Baxter equation in knot theory.
method Interpreting augmented racks in tensor categories and constructing solutions using quantum heaps and Hopf algebra modules.
result Explicit constructions and infinite families of Yang-Baxter solutions are provided.

We extend the rack algebra Z[X] defined by Andruskiewitsch and Grana to the case of biracks, enabling a notion of birack modules. We use these birack modules to define an enhancement of the birack counting invariant generalizing the birack module counting invariant in [8]. We provide examples demonstrating that the enh…

2011-03-01abs ↗pdf ↗