Double Cover

In mathematics, a double cover or double covering may refer to:

  • Double cover (topology), a two-to-one mapping from one topological space to another. Frequently occurring special cases include
    • The orientable double cover of a non-orientable manifold.
    • The bipartite double cover of an undirected graph G, formed by the graph tensor product G ×K2.
    • A double covering group of a topological group such as a Lie group, a group extension of index two formed by a topological double cover. A double cover may also be used to refer to non-topological group extensions of index two, for instance extensions of finite groups.
  • Cycle double cover, a collection of cycles in a graph that together include each edge twice. The cycle double cover conjecture is the unproven assertion that every bridgeless graph has a cycle double cover.

Double coverage may also refer to:

  • Double coverage, a defensive strategy in American football, basketball, and other sports
  • Being covered by more than one health insurance plan

Famous quotes containing the words double and/or cover:

    “You know, when these New Negroes have their convention—that is going to be the chairman of the Committee on Unending Agitation. Race, race, race!... Damn, even the N double A C P takes a holiday sometimes!”
    —Lorraine Hansberry (1930–1965)

    “He is a stranger to me but he is a most remarkable man—and I am the other one. Between us, we cover all knowledge; he knows all that can be known and I know the rest”
    —Mark Twain [Samuel Langhorne Clemens] (1835–1910)