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  2. Homotopy - Wikipedia

    en.wikipedia.org/wiki/Homotopy

    A notable use of homotopy is the definition of homotopy groups and cohomotopy groups, important invariants in algebraic topology. [3] In practice, there are technical difficulties in using homotopies with certain spaces. Algebraic topologists work with compactly generated spaces, CW complexes, or spectra.

  3. Homotopy group - Wikipedia

    en.wikipedia.org/wiki/Homotopy_group

    In mathematics, homotopy groups are used in algebraic topology to classify topological spaces. The first and simplest homotopy group is the fundamental group , denoted π 1 ( X ) , {\displaystyle \pi _{1}(X),} which records information about loops in a space .

  4. Algebraic topology - Wikipedia

    en.wikipedia.org/wiki/Algebraic_topology

    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 .

  5. Homotopy theory - Wikipedia

    en.wikipedia.org/wiki/Homotopy_theory

    In homotopy theory and algebraic topology, the word "space" denotes a topological space.In order to avoid pathologies, one rarely works with arbitrary spaces; instead, one requires spaces to meet extra constraints, such as being compactly generated weak Hausdorff or a CW complex.

  6. A¹ homotopy theory - Wikipedia

    en.wikipedia.org/wiki/A¹_homotopy_theory

    In algebraic geometry and algebraic topology, branches of mathematics, A 1 homotopy theory or motivic homotopy theory is a way to apply the techniques of algebraic topology, specifically homotopy, to algebraic varieties and, more generally, to schemes. The theory is due to Fabien Morel and Vladimir Voevodsky.

  7. 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.

  8. Homotopy extension property - Wikipedia

    en.wikipedia.org/wiki/Homotopy_extension_property

    In mathematics, in the area of algebraic topology, the homotopy extension property indicates which homotopies defined on a subspace can be extended to a homotopy defined on a larger space. The homotopy extension property of cofibrations is dual to the homotopy lifting property that is used to define fibrations .

  9. Homotopy groups of spheres - Wikipedia

    en.wikipedia.org/wiki/Homotopy_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 of spheres viewed as topological spaces , forgetting about their precise geometry.