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  2. Intersection number - Wikipedia

    en.wikipedia.org/wiki/Intersection_number

    There is an approach to intersection number, introduced by Snapper in 1959-60 and developed later by Cartier and Kleiman, that defines an intersection number as an Euler characteristic. Let X be a scheme over a scheme S , Pic( X ) the Picard group of X and G the Grothendieck group of the category of coherent sheaves on X whose support is proper ...

  3. Intersection number (graph theory) - Wikipedia

    en.wikipedia.org/wiki/Intersection_number_(graph...

    The intersection number of the graph is the smallest number such that there exists a representation of this type for which the union of the sets in has elements. [1] The problem of finding an intersection representation of a graph, using a given number of elements, is known as the intersection graph basis problem .

  4. Line–line intersection - Wikipedia

    en.wikipedia.org/wiki/Lineline_intersection

    The intersection point falls within the first line segment if 0 ≤ t ≤ 1, and it falls within the second line segment if 0 ≤ u ≤ 1. These inequalities can be tested without the need for division, allowing rapid determination of the existence of any line segment intersection before calculating its exact point.

  5. Witten conjecture - Wikipedia

    en.wikipedia.org/wiki/Witten_conjecture

    There are n line bundles L i on M g,n, whose fiber at a point of the moduli stack is given by the cotangent space of a Riemann surface at the marked point x i. The intersection index 〈τ d 1 , ..., τ d n 〉 is the intersection index of Π c 1 ( L i ) d i on M g , n where Σ d i = dim M g , n = 3 g – 3 + n , and 0 if no such g exists ...

  6. Union (set theory) - Wikipedia

    en.wikipedia.org/wiki/Union_(set_theory)

    In set theory, the union (denoted by ∪) of a collection of sets is the set of all elements in the collection. [1] It is one of the fundamental operations through which sets can be combined and related to each other. A nullary union refers to a union of zero (⁠ ⁠) sets and it is by definition equal to the empty set.

  7. Quadtree - Wikipedia

    en.wikipedia.org/wiki/Quadtree

    The intersection of two images is almost the same algorithm. One way to think about the intersection of the two images is that we are doing a union with respect to the white pixels. As such, to perform the intersection we swap the mentions of black and white in the union algorithm.

  8. Constructive solid geometry - Wikipedia

    en.wikipedia.org/wiki/Constructive_solid_geometry

    CSG objects can be represented by binary trees, where leaves represent primitives, and nodes represent operations. In this figure, the nodes are labeled ∩ for intersection, ∪ for union, and — for difference. Constructive solid geometry (CSG; formerly called computational binary solid geometry) is a technique used in solid modeling.

  9. Combinatorial design - Wikipedia

    en.wikipedia.org/wiki/Combinatorial_design

    A t-(v,k,λ) design D is quasi-symmetric with intersection numbers x and y (x < y) if every two distinct blocks intersect in either x or y points. These designs naturally arise in the investigation of the duals of designs with λ = 1. A non-symmetric (b > v) 2-(v,k,1) design is quasisymmetric with x = 0 and y = 1.