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  2. Base (topology) - Wikipedia

    en.wikipedia.org/wiki/Base_(topology)

    The set Γ of all open intervals in forms a basis for the Euclidean topology on .. A non-empty family of subsets of a set X that is closed under finite intersections of two or more sets, which is called a π-system on X, is necessarily a base for a topology on X if and only if it covers X.

  3. Subbase - Wikipedia

    en.wikipedia.org/wiki/Subbase

    Thus, we can start with a fixed topology and find subbases for that topology, and we can also start with an arbitrary subcollection of the power set ℘ and form the topology generated by that subcollection. We can freely use either equivalent definition above; indeed, in many cases, one of the two conditions is more useful than the other.

  4. Comparison of topologies - Wikipedia

    en.wikipedia.org/wiki/Comparison_of_topologies

    Let τ 1 and τ 2 be two topologies on a set X and let B i (x) be a local base for the topology τ i at x ∈ X for i = 1,2. Then τ 1 ⊆ τ 2 if and only if for all x ∈ X, each open set U 1 in B 1 (x) contains some open set U 2 in B 2 (x). Intuitively, this makes sense: a finer topology should have smaller neighborhoods.

  5. Special linear group - Wikipedia

    en.wikipedia.org/wiki/Special_linear_group

    The topology of SL(n, R) is the product of the topology of SO(n) and the topology of the group of symmetric matrices with positive eigenvalues and unit determinant. Since the latter matrices can be uniquely expressed as the exponential of symmetric traceless matrices, then this latter topology is that of (n + 2)(n − 1)/2-dimensional Euclidean ...

  6. Neighbourhood system - Wikipedia

    en.wikipedia.org/wiki/Neighbourhood_system

    Filters in topology – Use of filters to describe and characterize all basic topological notions and results. Locally convex topological vector space – Vector space with a topology defined by convex open sets; Neighbourhood (mathematics) – Open set containing a given point; Subbase – Collection of subsets that generate a topology

  7. Fundamental group - Wikipedia

    en.wikipedia.org/wiki/Fundamental_group

    The set of based loops (as is, i.e. not taken up to homotopy) in a pointed space X, endowed with the compact open topology, is known as the loop space, denoted . The fundamental group of X is in bijection with the set of path components of its loop space: [ 28 ]

  8. Topology - Wikipedia

    en.wikipedia.org/wiki/Topology

    A three-dimensional model of a figure-eight knot.The figure-eight knot is a prime knot and has an Alexander–Briggs notation of 4 1.. Topology (from the Greek words τόπος, 'place, location', and λόγος, 'study') is the branch of mathematics concerned with the properties of a geometric object that are preserved under continuous deformations, such as stretching, twisting, crumpling ...

  9. Topological data analysis - Wikipedia

    en.wikipedia.org/wiki/Topological_data_analysis

    In applied mathematics, topological data analysis (TDA) is an approach to the analysis of datasets using techniques from topology.Extraction of information from datasets that are high-dimensional, incomplete and noisy is generally challenging.