This is a **list of algebraic topology topics**, by Wikipedia page. See also:

- Homotopy
- Path (topology)
- Fundamental group
- Homotopy group
- Seifert–van Kampen theorem
- Pointed space
- Winding number
- Simply connected
- Monodromy
- Homotopy lifting property
- Mapping cylinder
- Mapping cone (topology)
- Wedge sum
- Smash product
- Adjunction space
- Cohomotopy
- Cohomotopy group
- Brown's representability theorem
- Eilenberg–MacLane space
- Fibre bundle
- Cofibration
- Homotopy groups of spheres
- Plus construction
- Whitehead theorem
- Weak equivalence
- Hurewicz theorem
- H-space

- Künneth theorem
- De Rham cohomology
- Obstruction theory
- Characteristic class
- Poincaré conjecture
- Cohomology operation
- Bott periodicity theorem
- K-theory
- Cobordism
- Thom space
- Suspension functor
- Stable homotopy theory
- Spectrum (homotopy theory)
- Morava K-theory
- Hodge conjecture
- Weil conjectures
- Directed algebraic topology

Example: DE-9IM

**Algebraic topology** is a branch of mathematics that uses tools from abstract algebra to study topological spaces. The basic goal is to find algebraic invariants that classify topological spaces up to homeomorphism, though usually most classify up to homotopy equivalence.

In mathematics, **homology** is a general way of associating a sequence of algebraic objects such as abelian groups or modules to other mathematical objects such as topological spaces. Homology groups were originally defined in algebraic topology. Similar constructions are available in a wide variety of other contexts, such as abstract algebra, groups, Lie algebras, Galois theory, and algebraic geometry.

In mathematics, specifically in homology theory and algebraic topology, **cohomology** is a general term for a sequence of abelian groups associated to a topological space, often defined from a cochain complex. Cohomology can be viewed as a method of assigning richer algebraic invariants to a space than homology. Some versions of cohomology arise by dualizing the construction of homology. In other words, cochains are functions on the group of chains in homology theory.

In mathematics, the **Hodge conjecture** is a major unsolved problem in the field of algebraic geometry that relates the algebraic topology of a non-singular complex algebraic variety to its subvarieties. More specifically, the conjecture states that certain de Rham cohomology classes are algebraic; that is, they are sums of Poincaré duals of the homology classes of subvarieties. It was formulated by the Scottish mathematician William Vallance Douglas Hodge as a result of a work in between 1930 and 1940 to enrich the description of de Rham cohomology to include extra structure that is present in the case of complex algebraic varieties. It received little attention before Hodge presented it in an address during the 1950 International Congress of Mathematicians, held in Cambridge, Massachusetts. The Hodge conjecture is one of the Clay Mathematics Institute's Millennium Prize Problems, with a prize of $1,000,000 for whoever can prove or disprove the Hodge conjecture.

In mathematics, a **sheaf** is a tool for systematically tracking locally defined data attached to the open sets of a topological space. The data can be restricted to smaller open sets, and the data assigned to an open set is equivalent to all collections of compatible data assigned to collections of smaller open sets covering the original one. For example, such data can consist of the rings of continuous or smooth real-valued functions defined on each open set. Sheaves are by design quite general and abstract objects, and their correct definition is rather technical. They are variously defined, for example, as sheaves of sets or sheaves of rings, depending on the type of data assigned to open sets.

In mathematics, a **line bundle** expresses the concept of a line that varies from point to point of a space. For example a curve in the plane having a tangent line at each point determines a varying line: the tangent bundle is a way of organising these. More formally, in algebraic topology and differential topology a line bundle is defined as a vector bundle of rank 1.

In mathematics, a **characteristic class** is a way of associating to each principal bundle of *X* a cohomology class of *X*. The cohomology class measures the extent the bundle is "twisted" — and whether it possesses sections. Characteristic classes are global invariants that measure the deviation of a local product structure from a global product structure. They are one of the unifying geometric concepts in algebraic topology, differential geometry, and algebraic geometry.

**Algebraic K-theory** is a subject area in mathematics with connections to geometry, topology, ring theory, and number theory. Geometric, algebraic, and arithmetic objects are assigned objects called

In mathematics, in the subfield of geometric topology, the **mapping class group** is an important algebraic invariant of a topological space. Briefly, the mapping class group is a certain discrete group corresponding to symmetries of the space.

In algebraic topology, a branch of mathematics, a **spectrum** is an object representing a generalized cohomology theory. There are several different categories of spectra, but they all determine the same homotopy category, known as the **stable homotopy category**.

In mathematics, **sheaf cohomology** is the application of homological algebra to analyze the global sections of a sheaf on a topological space. Broadly speaking, sheaf cohomology describes the obstructions to solving a geometric problem globally when it can be solved locally. The central work for the study of sheaf cohomology is Grothendieck's 1957 Tôhoku paper.

In mathematics, and algebraic topology in particular, an **Eilenberg–MacLane space** is a topological space with a single nontrivial homotopy group. As such, an Eilenberg–MacLane space is a special kind of topological space that can be regarded as a building block for homotopy theory; general topological spaces can be constructed from these via the Postnikov system. These spaces are important in many contexts in algebraic topology, including constructions of spaces, computations of homotopy groups of spheres, and definition of cohomology operations. The name is for Samuel Eilenberg and Saunders Mac Lane, who introduced such spaces in the late 1940s.

In noncommutative geometry and related branches of mathematics, **cyclic homology** and **cyclic cohomology** are certain (co)homology theories for associative algebras which generalize the de Rham (co)homology of manifolds. These notions were independently introduced by Boris Tsygan (homology) and Alain Connes (cohomology) in the 1980s. These invariants have many interesting relationships with several older branches of mathematics, including de Rham theory, Hochschild (co)homology, group cohomology, and the K-theory. Contributors to the development of the theory include Max Karoubi, Yuri L. Daletskii, Boris Feigin, Jean-Luc Brylinski, Mariusz Wodzicki, Jean-Louis Loday, Victor Nistor, Daniel Quillen, Joachim Cuntz, Ryszard Nest, Ralf Meyer, and Michael Puschnigg.

In mathematics, specifically in algebraic geometry and algebraic topology, the **Lefschetz hyperplane theorem** is a precise statement of certain relations between the shape of an algebraic variety and the shape of its subvarieties. More precisely, the theorem says that for a variety *X* embedded in projective space and a hyperplane section *Y*, the homology, cohomology, and homotopy groups of *X* determine those of *Y*. A result of this kind was first stated by Solomon Lefschetz for homology groups of complex algebraic varieties. Similar results have since been found for homotopy groups, in positive characteristic, and in other homology and cohomology theories.

In mathematics, the **Hodge–de Rham spectral sequence**, also known as the **Frölicher spectral sequence** computes the cohomology of a complex manifold.

This is a glossary of properties and concepts in algebraic topology in mathematics.

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Images, videos and audio are available under their respective licenses.