The nonuniqueness of Chekanov polynomials of Legendrian knots.
The number of independent Vassiliev invariants in the Homfly and Kauffman polynomials.
The ?-orbifold Group of a Link.
The orbits of the Hurwitz action of the braid groups on the standard generators
The Hurwitz action of the n-braid group Bₙ on the n-fold direct product of the m-braid group is studied. We show that the orbit of any n- tuple of the n standard generators of consists of the (n-1)th powers of n+1 elements.
The -central extension of the Mapping Class Group of orientable surfaces
Topological Quantum Field Theories are closely related to representations of Mapping Class Groups of surfaces. Considering the case of the TQFTs derived from the Kauffman bracket, we describe the central extension coming from this representation, which is just a projective extension.
The proof of Birman's conjecture on singular braid monoids.
The QSF property for groups and spaces.
The rank of actions on -trees
The real genus of the alternating groups.
The recognition problem for topological manifolds
The reduction of quantum invariants of 4-thickenings
We study the sensibility of an invariant of 2-dimensional CW complexes in the case when it comes as a reduction (through a change of ring) of a modular invariant of 4-dimensional thickenings of such complexes: it is shown that if the Euler characteristic of the 2-complex is greater than or equal to 1, its invariant depends only on homology. To see what is happening when the Euler characteristic is smaller than 1, we use ideas of Kerler and construct, from any tortile category, an invariant of 4-thickenings...
The reflexible hypermaps of characteristic
The regular projective solution space of the figure-eight knot complement.
The representation theory and the branching graph for the family of Turaev algebras .
The representation theory of the Temperley-Lieb algebras.
The rhombic dodecahedron and semisimple actions of Aut(Fₙ) on CAT(0) spaces
We consider actions of automorphism groups of free groups by semisimple isometries on complete CAT(0) spaces. If n ≥ 4 then each of the Nielsen generators of Aut(Fₙ) has a fixed point. If n = 3 then either each of the Nielsen generators has a fixed point, or else they are hyperbolic and each Nielsen-generated ℤ⁴ ⊂ Aut(F₃) leaves invariant an isometrically embedded copy of Euclidean 3-space 𝔼³ ↪ X on which it acts as a discrete group of translations with the rhombic dodecahedron as a Dirichlet...
The Seiberg-Witten invariants and 4-manifolds with essential tori.
The Seiberg–Witten invariants of negative definite plumbed 3-manifolds
Assume that is a connected negative definite plumbing graph, and that the associated plumbed 3-manifold is a rational homology sphere. We provide two new combinatorial formulae for the Seiberg–Witten invariant of . The first one is the constant term of a ‘multivariable Hilbert polynomial’, it reflects in a conceptual way the structure of the graph , and emphasizes the subtle parallelism between these topological invariants and the analytic invariants of normal surface singularities. The second...
The Semiclassical Electron in a Magnetic Field and Lattice. Some Problems of Low Dimensional "Periodic" Topology.
The shape of a group---connections between shape theory and the homology of groups