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:

    “To be a woman and a writer
    is double mischief, for
    the world will slight her
    who slights “the servile house,” and who would rather
    make odes than beds.”
    —Dilys Laing (1906–1960)

    “If I use the media, even with tricks, to publicise a black youth being shot in the back in Teaneck, New Jersey ... then I should be praised for it, and it’s more of a comment on them than me that it would take tricks to make them cover the loss of life.”
    —Al, Rev. Sharpton (b. 1954)