Search results for " Geometria"

A note on relative isoclinism classes of compact groups

2009

On some recent investigations of probability in group theory

2010

We describe some recent contributions on the probability of commuting pairs, introduced by P. Erdos, W. Gustafson and P. Turan around 1968 and 1973. Both combinatorial methods and character theory have significant application in this context and we illustrate some standard techniques and strategies, once generalizations of the probability of commuting pairs want to be studied. The importance of the subject is emphasized in some remarks and open questions, which reformulate some classical conjectures in group theory via a probabilistic approach.

The generalized commutativity degree in a finite group

2009

Conjugately dense subgroups in generalized $FC$-groups

2009

The ziqqurath of exact sequences of n-groupoids

2011

In this work we study exactness in the sesqui-category of n-groupoids. Using homotopy pullbacks, we construct a six term sequence of (n-1)-groupoids from an n-functor between pointed n-groupoids. We show that the sequence is exact in a suitable sense, which generalizes the usual notions of exactness for groups and categorical groups. Moreover, iterating the process, we get a ziqqurath of exact sequences of increasing length and decreasing dimension. For n = 1 we recover a classical result due to R. Brown and, for n = 2 its generalizations due to Hardie, Kamps and Kieboom and to Duskin, Kieboom and Vitale.

On a result of L.-C. Kappe and M. Newell

2009

There is a long line of research investigating upper central series of a group. The interest comes from the information which these series can give on the structure of a group. Baer (1952) extended the usual notion of center of a group, introducing that of p-centre, where p is a prime. Almost 40 years later, Kappe and Newell (1989) were able to embed the p-centre of a metabelian p-group in the p-th term of the upper central series. This was possible because of the growing knowledge on Engel groups of the 60s years. Here we extend the result of Kappe and Newell (1989) to wider classes of groups.

A note about additive designs

2008

Topologie à l'infini et variétés à géométrie bornée

2013

We give a quick review on the asymptotic topology and the geometry of manifolds with bounded geometry, by quoting also some results obtained by the authors.

A counterexample to a conjecture on linear systems on ℙ3

2004

In this paper [1] Ciliberto proposes a conjecture in order to characterize special linear systems of IPn through multiple base points. In this note we give a counterexample to this conjecture by showing that there is a substantial difference between the speciality of linear systems on IP 2 and those of IP3.

The action of the unitary group associated with a quadratic extension of fields

1999

Given a quadratic extension L/k of fields of characteristic different from 2 and a unitary space (V, f) of finite dimension over L, we give a representation, as simple as possible, of the form which f induces by restriction on a k-substructure of V. This, in turn, allows one to study the orbits of the unitary group U(V, f) in the set of k-substructures of V of a given dimension.