Ext-groups

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• Ext functor — In mathematics, the Ext functors of homological algebra are derived functors of Hom functors. They were first used in algebraic topology, but are common in many areas of mathematics. Definition and computation Let R be a ring and let mathrm{Mod}… …   Wikipedia

• International Organizations and Groups — Note: The Socialist Federal Republic of Yugoslavia (SFRY) has dissolved and ceases to exist. None of the successor states of the former Yugoslavia, including Serbia and Montenegro, have been permitted to participate solely on the basis of the… …   Universalium

• Group cohomology — This article is about homology and cohomology of a group. For homology or cohomology groups of a space or other object, see Homology (mathematics). In abstract algebra, homological algebra, algebraic topology and algebraic number theory, as well… …   Wikipedia

• Kazhdan–Lusztig polynomial — In representation theory, a Kazhdan–Lusztig polynomial P y,w ( q ) is a member of a family of integral polynomials introduced in work of David Kazhdan and George Lusztig Harv|Kazhdan|Lusztig|1979. They are indexed by pairs of elements y , w of a… …   Wikipedia

• Spectral sequence — In the area of mathematics known as homological algebra, especially in algebraic topology and group cohomology, a spectral sequence is a means of computing homology groups by taking successive approximations. Spectral sequences are a… …   Wikipedia

• Sheaf extension — In Sheaf theory (a branch of the mathematics area of algebraic geometry), a sheaf extension is a way of describing a sheaf in terms of a subsheaf and a quotient sheaf, analogous to a how a group extension describes a group in terms of a subgroup …   Wikipedia

• Floer homology — is a mathematical tool used in the study of symplectic geometry and low dimensional topology. First introduced by Andreas Floer in his proof of the Arnold conjecture in symplectic geometry, Floer homology is a novel homology theory arising as an… …   Wikipedia

• Adams spectral sequence — In mathematics, the Adams spectral sequence is a spectral sequence introduced by Adams (1958). Like all spectral sequences, it is a computational tool; it relates homology theory to what is now called stable homotopy theory. It is a… …   Wikipedia

• Doomsday conjecture — In algebraic topology, the doomsday conjecture was a conjecture about Ext groups over the Steenrod algebra made by Joel Cohen, named by Michael Barratt, published by Milgram (1971, conjecture 73) and disproved by Mahowald (1977). Minami (1995)… …   Wikipedia

• Model category — In mathematics, particularly in homotopy theory, a model category is a category with distinguished classes of morphisms ( arrows ) called weak equivalences , fibrations and cofibrations . These abstract from a conventional homotopy category, of… …   Wikipedia

• Uwe Jannsen — (* 11. März 1954) ist ein deutscher Mathematiker, der sich mit Algebra, algebraischer Zahlentheorie und algebraischer Geometrie beschäftigt. Jannsen in Oberwolfach 2009 Inhaltsverzeichnis 1 …   Deutsch Wikipedia