Cohomology of unipotent algebraic and finite groups and the Steenrod algebra.
Cohomology rings of Artin groups
In this paper integer cohomology rings of Artin groups associated with exceptional groups are determined. Computations have been carried out by using an effective method for calculation of cup product in cellular cohomology which we introduce here. Actually, our method works in general for any finite regular complex with identifications, the regular complex being geometrically realized by a compact orientable manifold, possibly with boundary.
Cohomology rings of spaces of generic bipolynomials and extended affine Weyl groups of serie
A bipolynomial is a holomorphic mapping of a sphere onto a sphere such that some point on the target sphere has exactly two preimages. The topological invariants of spaces of bipolynomials without multiple roots are connected with characteristic classes of rational functions with two poles and generalized braid groups associated to extended affine Weyl groups of the serie . We prove that the cohomology rings of the spaces of bipolynomials of bidegree stabilize as tends to infinity and that...
Cohomology with free coefficients of the fundamental group of a graph of groups.
Coleman automorphisms of finite groups with a self-centralizing normal subgroup
Let be a finite group with a normal subgroup such that . It is shown that under some conditions, Coleman automorphisms of are inner. Interest in such automorphisms arose from the study of the normalizer problem for integral group rings.
Colimits of representable algebra-valued functors.
Collineation group as a subgroup of the symmetric group
Let ψ be the projectivization (i.e., the set of one-dimensional vector subspaces) of a vector space of dimension ≥ 3 over a field. Let H be a closed (in the pointwise convergence topology) subgroup of the permutation group of the set ψ. Suppose that H contains the projective group and an arbitrary self-bijection of ψ transforming a triple of collinear points to a non-collinear triple. It is well known from [Kantor W.M., McDonough T.P., On the maximality of PSL(d+1,q), d ≥ 2, J. London Math. Soc.,...
Collineation Groups of Finite Projective Planes Whose Sylow 2-Subgroups Contain at most Three Involutions.
Collineation groups of translation planes of small dimension.
Coloured generalised Young diagrams for affine Weyl-Coxeter groups.
Combination of convergence groups.
Combinatorial and group-theoretic compactifications of buildings
Let be a building of arbitrary type. A compactification of the set of spherical residues of is introduced. We prove that it coincides with the horofunction compactification of endowed with a natural combinatorial distance which we call the root-distance. Points of admit amenable stabilisers in and conversely, any amenable subgroup virtually fixes a point in . In addition, it is shown that, provided is transitive enough, this compactification also coincides with the group-theoretic...
Combinatorial aspects of code loops
The existence and uniqueness (up to equivalence defined below) of code loops was first established by R. Griess in [3]. Nevertheless, the explicit construction of code loops remained open until T. Hsu introduced the notion of symplectic cubic spaces and their Frattini extensions, and pointed out how the construction of code loops followed from the (purely combinatorial) result of O. Chein and E. Goodaire contained in [2]. Within this paper, we focus on their combinatorial construction and prove...
Combinatorial differential geometry and ideal Bianchi–Ricci identities II – the torsion case
This paper is a continuation of [2], dealing with a general, not-necessarily torsion-free, connection. It characterizes all possible systems of generators for vector-field valued operators that depend naturally on a set of vector fields and a linear connection, describes the size of the space of such operators and proves the existence of an ‘ideal’ basis consisting of operators with given leading terms which satisfy the (generalized) Bianchi–Ricci identities without corrections.
Combinatorial Laplacian of the matching complex.
Combinatorial mapping-torus, branched surfaces and free group automorphisms
We give a characterization of the geometric automorphisms in a certain class of (not necessarily irreducible) free group automorphisms. When the automorphism is geometric, then it is induced by a pseudo-Anosov homeomorphism without interior singularities. An outer free group automorphism is given by a -cocycle of a -complex (a standard dynamical branched surface, see [7] and [9]) the fundamental group of which is the mapping-torus group of the automorphism. A combinatorial construction elucidates...
Combinatorial Modulus on Boundary of Right-Angled Hyperbolic Buildings
In this article, we discuss the quasiconformal structure of boundaries of right-angled hyperbolic buildings using combinatorial tools. In particular, we exhibit some examples of buildings of dimension 3 and 4 whose boundaries satisfy the combinatorial Loewner property. This property is a weak version of the Loewner property. This is motivated by the fact that the quasiconformal structure of the boundary led to many results of rigidity in hyperbolic spaces since G.D.Mostow. In the case of buildings...
Combinatorial operators for Kronecker powers of representations of .
Combinatorial polarization, code loops, and codes of high level.
Combinatorial properties of products of graphs