Protomodularity, descent, and semidirect products.
Q-perfect groups and universal Q-central extensions.
Using results of Ellis-Rodríguez Fernández, an explicit description by generators and relations is given of the mod q Schur multiplier, and this is shown to be the kernel of a universal q-central extension in the case of a q-perfect group, i.e. one which is generated by commutators and q-th powers. These results generalise earlier work [by] K. Dennis and Brown-Loday.
Quillen Stratification for Modules.
Rational and Generic Cohomology
Rational Representations of Finite Groups and Their Euler Class.
Realizing maps between modules over Tate cohomology rings.
Reedy categories which encode the notion of category actions
We study a certain type of action of categories on categories and on operads. Using the structure of the categories Δ and Ω governing category and operad structures, respectively, we define categories which instead encode the structure of a category acting on a category, or a category acting on an operad. We prove that the former has the structure of an elegant Reedy category, whereas the latter has the structure of a generalized Reedy category. In particular, this approach gives a new way to regard...
Relation modules of finite groups and related topics.
Relations among certain number knots
Relative cohomolgy of groups.
Relative cyclic homology and the Bass conjecture.
Relative derived functors and the homology of groups
Remarks on free Bieberbach Groups.
Remarks on the Mal'cev completion of torsion-free locally nilpotent groups
Representations linearies et compactification profinie des groupes discrets.
Resolutions of moduli spaces and homological stability
We describe partial semi-simplicial resolutions of moduli spaces of surfaces with tangential structure. This allows us to prove a homological stability theorem for these moduli spaces, which often improves the known stability ranges and gives explicit stability ranges in many new cases. In each of these cases the stable homology can be identified using the methods of Galatius, Madsen, Tillmann and Weiss.
Salvetti complex, spectral sequences and cohomology of Artin groups
The aim of this short survey is to give a quick introduction to the Salvetti complex as a tool for the study of the cohomology of Artin groups. In particular we show how a spectral sequence induced by a filtration on the complex provides a very natural and useful method to study recursively the cohomology of Artin groups, simplifying many computations. In the last section some examples of applications are presented.
Schur multipliers of p-groups.
Séries de compositions de modules instables et injectivité de la cohomologie du groupe Z/2.
Simplicial crossed modules and mapping cones.