Stalk (sheaf)The stalk of a sheaf is a mathematical construction capturing the behaviour of a sheaf around a given point. Sheaves are defined on open sets, but the underlying topological space consists of points. It is reasonable to attempt to isolate the behavior of a sheaf at a single fixed point of . Conceptually speaking, we do this by looking at small neighborhoods of the point. If we look at a sufficiently small neighborhood of , the behavior of the sheaf on that small neighborhood should be the same as the behavior of at that point.
Constant sheafIn mathematics, the constant sheaf on a topological space associated to a set is a sheaf of sets on whose stalks are all equal to . It is denoted by or . The constant presheaf with value is the presheaf that assigns to each non-empty open subset of the value , and all of whose restriction maps are the identity map . The constant sheaf associated to is the sheafification of the constant presheaf associated to . This sheaf identifies with the sheaf of locally constant -valued functions on .
Cohomologie de ČechLa cohomologie de Čech est une théorie cohomologique, développée à l'origine par le mathématicien Eduard Čech en faisant jouer au nerf d'un recouvrement sur un espace topologique le rôle des simplexes en homologie simpliciale. On peut définir une cohomologie de Čech pour les faisceaux, ou plus généralement pour les objets d'un site, en particulier une catégorie de schémas munie de la topologie de Zariski.
Morphism of algebraic varietiesIn algebraic geometry, a morphism between algebraic varieties is a function between the varieties that is given locally by polynomials. It is also called a regular map. A morphism from an algebraic variety to the affine line is also called a regular function. A regular map whose inverse is also regular is called biregular, and the biregular maps are the isomorphisms of algebraic varieties.
Leray spectral sequenceIn mathematics, the Leray spectral sequence was a pioneering example in homological algebra, introduced in 1946 by Jean Leray. It is usually seen nowadays as a special case of the Grothendieck spectral sequence. Let be a continuous map of topological spaces, which in particular gives a functor from sheaves of abelian groups on to sheaves of abelian groups on .
Filtered categoryIn , filtered categories generalize the notion of directed set understood as a category (hence called a directed category; while some use directed category as a synonym for a filtered category). There is a dual notion of cofiltered category, which will be recalled below. A is filtered when it is not empty, for every two objects and in there exists an object and two arrows and in , for every two parallel arrows in , there exists an object and an arrow such that . A filtered colimit is a colimit of a functor where is a filtered category.
Battle of Sept-ÎlesThe Battle of Sept-Îles was a naval action fought on the night of 22/23 October 1943 during World War II as part of the Atlantic campaign. The battle took place off the Sept-Îles near the French coast in the English Channel between a light cruiser and six destroyers of the British Royal Navy hoping to intercept, a German blockade runner, which was accompanied by German torpedo-boat destroyers flotillas of the German Kriegsmarine.
Sept-ÎlesSept-Îles ( ; en innu-aimun : Uashat mak Mani-utenam) est une ville de la municipalité régionale de comté de Sept-Rivières, dans la région administrative de la Côte-Nord, au Québec. La ville de Sept-Îles se trouve juste au-dessus du , sur le littoral nord du golfe du Saint-Laurent, approximativement à à l'est de Baie-Comeau. À la suite d'une fusion le 12 février 2003, la ville actuelle de Sept-Îles rassemble les anciennes municipalités de Gallix et de Moisie.
Arthur Verhaegenthumb|Vue sur le nouveau Grand béguinage de Gand, dernier béguinage en activité construit en Europe de 1872 à 1875 et dessiné par Arthur Verhaegen en collaboration avec Jean-Baptiste Bethune. Arthur Verhaegen, né le à Bruxelles et mort le à Ixelles, est un ingénieur, architecte, décorateur, homme politique, écrivain et résistant belge. Arthur Verhaegen est le fils ainé de l’avocat Jean Baptiste François Eugène Verhaegen (1820-1878) et de Marie Florentine Caroline Joséphine Nève (1832-1903).
EftelingEfteling est un parc d'attractions et complexe de loisirs néerlandais situé dans le village de Kaatsheuvel, dans le Brabant-Septentrional. Ayant pour thème les contes et légendes, il est l'un des plus anciens parcs de loisirs en activité puisque ses racines remontent en 1935 lorsque deux clercs locaux fondent un terrain de jeux. Officiellement inauguré le avec le Bois des Contes de fées, il est remarqué par l'unité de son style : celui de l’illustrateur de contes pour enfants Anton Pieck (1895-1987).
Elections in VenetoThis page gathers the results of elections in Veneto. Veneto has always been characterised by the big role played by the Catholic Church and centrist politics, but was also an early stronghold of the Radical Party and the Italian Socialist Party. In 1919, in the first election with male universal suffrage, the Catholic-inspired Italian People's Party won 42.6% of the vote and the Italian Socialist Party 36.2%.
Mahnaz ShiraliMahnaz Shirali, née en 1965 à Téhéran, est une sociologue et politologue iranienne. Elle est directrice d'études à l'Institut de science et de théologie des religions de Paris, directrice d'études à l'Institut catholique de Paris (ICP) et enseignante à Science Po Paris. Elle est spécialiste de l'Iran. Elle est auteure de plusieurs livres sur l'Iran et s'intéresse de manière profonde à l'Islam et aux régimes islamiques. Mahnaz Shirali est née à Téhéran, en Iran.
