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:
“I grew up confidently expecting to have a profession and earn my own living, and also confidently expecting to be married and have children. It was fifty-fifty with me. I was just as passionately determined to have children as I was to have a career. And my mother was the triumphant answer to all doubts as to the success of this double role. From my earliest memory she had more than half supported the family and yet she was supremely a mother.”
—Crystal Eastman (1881–1928)
“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)