2-Gerbes bound by complexes of gr-stacks, and cohomology

We define 2-gerbes bound by complexes of braided group-like stacks. We prove a classification result in terms of hypercohomology groups with values in abelian crossed squares and cones of morphisms of complexes of length 3. We give an application to the geometric construction of certain elements in Hermitian Deligne cohomology groups.Comment: 70 pages, latex+amsmath+xypi

Butterflies II: Torsors for 2-group stacks

We study torsors over 2-groups and their morphisms. In particular, we study the first non-abelian cohomology group with values in a 2-group. Butterfly diagrams encode morphisms of 2-groups and we employ them to examine the functorial behavior of non-abelian cohomology under change of coefficients. We re-interpret the first non-abelian cohomology with coefficients in a 2-group in terms of gerbes bound by a crossed module. Our main result is to provide a geometric version of the change of coefficients map by lifting a gerbe along the "fraction" (weak morphism) determined by a butterfly. As a practical byproduct, we show how butterflies can be used to obtain explicit maps at the cocycle level. In addition, we discuss various commutativity conditions on cohomology induced by various degrees of commutativity on the coefficient 2-groups, as well as specific features pertaining to group extensions.Comment: 57 pages; typos fixed; some comments added. To appear in Adv. in Mathematic

Cohomologie à valeurs dans un faisceau de groupes croisés sur un site (II)

Debremaeker Raymond. Cohomologie à valeurs dans un faisceau de groupes croisés sur un site (II). In: Bulletin de la Classe des sciences, tome 63, 1977. pp. 765-772

Cohomologie à valeurs dans un faisceau de groupes croisés sur un site (I)

Debremaeker Raymond. Cohomologie à valeurs dans un faisceau de groupes croisés sur un site (I). In: Bulletin de la Classe des sciences, tome 63, 1977. pp. 758-764

The effect of quadratic transformations on degree functions

status: publishe

Luminescence control in the brittlestar Amphipholis squamata: Effect of cholinergic drugs

Potassium chloride and cholinergic drugs were rested on isolated arms of Amphipholis squamata; potassium chloride triggered a monophasic light emission; acetylcholine (10(-3) M) induced a luminescent response characterized by multiple flashes. ACh luminescence was increased in the presence of the cholinesterase inhibitor, eserine. Nicotinic antagonists, tubocurarine and hexamethonium chloride, had no inhibitory effect on the luminescence; muscarinic antagonists, atropine and benzotropine mesylate inhibited Amphipholis luminescence. These results suggest that the luminescence in A. squamata is mediated through a muscarinic cholinergic system. Copyright (C) 1996 Elsevier Science Inc