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Zig-zag Lemma
In mathematics, particularly homological algebra, the zig-zag lemma asserts the existence of a particular long exact sequence in the homology groups of certain chain complexes. The result is valid in every abelian category. Statement In an abelian category (such as the category of abelian groups or the category of vector spaces over a given field), let (\mathcal,\partial_), (\mathcal,\partial_') and (\mathcal,\partial_'') be chain complexes that fit into the following short exact sequence: : 0 \longrightarrow \mathcal \mathrel \mathcal \mathrel \mathcal\longrightarrow 0 Such a sequence is shorthand for the following commutative diagram: commutative diagram representation of a short exact sequence of chain complexes where the rows are exact sequences and each column is a chain complex. The zig-zag lemma asserts that there is a collection of boundary maps : \delta_n : H_n(\mathcal) \longrightarrow H_(\mathcal), that makes the following sequence exact: long exact seque ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mathematics
Mathematics is an area of knowledge that includes the topics of numbers, formulas and related structures, shapes and the spaces in which they are contained, and quantities and their changes. These topics are represented in modern mathematics with the major subdisciplines of number theory, algebra, geometry, and analysis, respectively. There is no general consensus among mathematicians about a common definition for their academic discipline. Most mathematical activity involves the discovery of properties of abstract objects and the use of pure reason to prove them. These objects consist of either abstractions from nature orin modern mathematicsentities that are stipulated to have certain properties, called axioms. A ''proof'' consists of a succession of applications of deductive rules to already established results. These results include previously proved theorems, axioms, andin case of abstraction from naturesome basic properties that are considered true starting points of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
