Seminormal graded rings and weakly normal projective varieties.
Smash products for -sets, Clifford theory and duality theorems.
Smash products, group actions and group graded rings.
Smooth invariants and -graded modules over
It is shown that every -graded module over is a direct sum of cyclics. The invariants for such modules are exactly the smooth invariants of valuated abelian -groups.
Some algebraic applications of graded categorical group theory.
Some graded radicals of graded rings.
Some remarks on normal property of graded subalgebras of polynomial rings.
s-rings and modular representations.
Stable Clifford theory for divisorially graded rings.
Strongly graded left FTF rings.
An associated ring R with identity is said to be a left FTF ring when the class of the submodules of flat left R-modules is closed under injective hulls and direct products. We prove (Theorem 3.5) that a strongly graded ring R by a locally finite group G is FTF if and only if Re is left FTF, where e is a neutral element of G. This provides new examples of left FTF rings. Some consequences of this Theorem are given.
Strongly groupoid graded rings and cohomology
We interpret the collection of invertible bimodules as a groupoid and call it the Picard groupoid. We use this groupoid to generalize the classical construction of crossed products to what we call groupoid crossed products, and show that these coincide with the class of strongly groupoid graded rings. We then use groupoid crossed products to obtain a generalization from the group graded situation to the groupoid graded case of the bijection from a second cohomology group, defined by the grading...
Superlinear algebra or two-graded algebraic structures.
Sur certaines algèbres de Lie de dérivations
Il est démontré que toute a.d.g.c. ayant un modèle minimal de Sullivan de type fini peut être représentée par une certaine algèbre de Lie différentielle graduée de dérivations. En particulier on peut ainsi représenter le type d’homotopie rationnelle d’un espace topologique.
Symmetric Functions, Conjugacy Classes and the Flag Variety.
Systèmes dynamiques contraints : l'approche homologique
On décrit une approche homologique des systèmes dynamiques contraints. Cette approche, directement inspirée des travaux de D. McMullan et de M. Henneaux concernant le formalisme de Batalin, Fradkin et Vilkovisky, contient une interprétation des fantômes et de leurs conjugués. Dans le cadre des systèmes dans l’espace des phases, la construction se fait en deux étapes. La première étape consiste à construire une algèbre différentielle graduée dont la cohomologie en degré zéro est l’espace des observables...