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  2. Topological group - Wikipedia

    en.wikipedia.org/wiki/Topological_group

    An action of a topological group G on a topological space X is a group action of G on X such that the corresponding function G × X → X is continuous. Likewise, a representation of a topological group G on a real or complex topological vector space V is a continuous action of G on V such that for each g ∈ G, the map v ↦ gv from V to ...

  3. Algebraic topology - Wikipedia

    en.wikipedia.org/wiki/Algebraic_topology

    In mathematics, homotopy groups are used in algebraic topology to classify topological spaces. The first and simplest homotopy group is the fundamental group, which records information about loops in a space. Intuitively, homotopy groups record information about the basic shape, or holes, of a topological space.

  4. Homotopy group - Wikipedia

    en.wikipedia.org/wiki/Homotopy_group

    Homotopy groups are such a way of associating groups to topological spaces. A torus A sphere. That link between topology and groups lets mathematicians apply insights from group theory to topology. For example, if two topological objects have different homotopy groups, they cannot have the same topological structure—a fact that may be ...

  5. List of general topology topics - Wikipedia

    en.wikipedia.org/wiki/List_of_general_topology...

    Topological space; Topological property; Open set, closed set. Clopen set; Closure (topology) Boundary (topology) Dense (topology) G-delta set, F-sigma set; closeness (mathematics) neighbourhood (mathematics) Continuity (topology) Homeomorphism; Local homeomorphism; Open and closed maps; Germ (mathematics) Base (topology), subbase; Open cover ...

  6. Fundamental group - Wikipedia

    en.wikipedia.org/wiki/Fundamental_group

    In the mathematical field of algebraic topology, the fundamental group of a topological space is the group of the equivalence classes under homotopy of the loops contained in the space. It records information about the basic shape, or holes, of the topological space. The fundamental group is the first and simplest homotopy group.

  7. Category:Topological groups - Wikipedia

    en.wikipedia.org/wiki/Category:Topological_groups

    In mathematics, a topological group G is a group that is also a topological space such that the group multiplication G × G→G and the inverse operation G→G are continuous maps. Subcategories This category has the following 2 subcategories, out of 2 total.

  8. Totally disconnected group - Wikipedia

    en.wikipedia.org/wiki/Totally_disconnected_group

    Such topological groups are necessarily Hausdorff. Interest centres on locally compact totally disconnected groups (variously referred to as groups of td-type, [1] locally profinite groups, [2] or t.d. groups [3]). The compact case has been heavily studied – these are the profinite groups – but for a long time not much was known about the ...

  9. Seifert–Van Kampen theorem - Wikipedia

    en.wikipedia.org/wiki/Seifert–van_Kampen_theorem

    In mathematics, the Seifert–Van Kampen theorem of algebraic topology (named after Herbert Seifert and Egbert van Kampen), sometimes just called Van Kampen's theorem, expresses the structure of the fundamental group of a topological space in terms of the fundamental groups of two open, path-connected subspaces that cover. It can therefore be ...