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Cohomotopy Groups
In mathematics, particularly algebraic topology, cohomotopy sets are particular contravariant functors from the category of pointed topological spaces and basepoint-preserving continuous maps to the category of sets and functions. They are dual to the homotopy groups, but less studied. Overview The ''p''-th cohomotopy set of a pointed topological space ''X'' is defined by :\pi^p(X) = ,S^p/math> the set of pointed homotopy classes of continuous mappings from X to the ''p''-sphere S^p. For ''p'' = 1 this set has an abelian group structure, and, provided X is a CW-complex, is isomorphic to the first cohomology group H^1(X), since the circle S^1 is an Eilenberg–MacLane space of type K(\mathbb,1). In fact, it is a theorem of Heinz Hopf that if X is a CW-complex of dimension at most ''p'', then ,S^p/math> is in bijection with the ''p''-th cohomology group H^p(X). The set ,S^p/math> also has a natural group structure if X is a suspension \Sigma Y, such as a sphere S^q f ... [...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 t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
