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:

    “American families, however, without exception, experience a double message in our society, one that claims a commitment to families and stresses the importance of raising bright, stable, productive citizens, yet remains so bound by an ideal of “rugged individualism” that parents receive little support in their task from the public or private sectors.”
    —Bernice Weissbourd (20th century)

    “Nothing can we call our own but death,
    And that small model of the barren earth
    Which serves as paste and cover to our bones.”
    —William Shakespeare (1564–1616)