homology group
51Algebraic topology — is a branch of mathematics which uses tools from abstract algebra to study topological spaces. The basic goal is to find algebraic invariants that classify topological spaces up to homeomorphism. In many situations this is too much to hope for… …
52Spectral 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… …
53Schur multiplier — In mathematical group theory, the Schur multiplier or Schur multiplicator is the second homology group of a group G. It was introduced by Issai Schur (1904) in his work on projective representations. Contents 1 Examples and properties 2 Re …
54Seifert fiber space — A Seifert fiber space is a 3 manifold together with a nice decomposition as a disjoint union of circles. In other words it is a S^1 bundle (circle bundle) over a 2 dimensional orbifold. Most small 3 manifolds are Seifert fiber spaces, and they… …
55Poincaré duality — In mathematics, the Poincaré duality theorem, named after Henri Poincaré, is a basic result on the structure of the homology and cohomology groups of manifolds. It states that if M is an n dimensional compact oriented manifold, then the k th… …
56Orientability — For orientation of vector spaces, see orientation (mathematics). For other uses, see Orientation (disambiguation). The torus is an orientable surface …
57Acyclic space — In mathematics, an acyclic space is a topological space X in which cycles are always boundaries, in the sense of homology theory. This implies that the integral homology groups in all dimensions of X are isomorphic to the corresponding homology… …
58Hurewicz theorem — In mathematics, the Hurewicz theorem is a basic result of algebraic topology, connecting homotopy theory with homology theory via a map known as the Hurewicz homomorphism. The theorem is named after Witold Hurewicz, and generalizes earlier… …
59Homotopy groups of spheres — In the mathematical field of algebraic topology, the homotopy groups of spheres describe how spheres of various dimensions can wrap around each other. They are examples of topological invariants, which reflect, in algebraic terms, the structure… …
60Size function — Size functions are shape descriptors, in a geometrical/topological sense. They are functions from the half plane to the natural numbers, counting certain connected components of a topological space. They are used in pattern recognition and… …
