In the case of characteristic 2 the double cover may need to be an inseparable covering.

If the 3-manifold has no connected double covers then all its boundary components are 2-spheres.

This is a double cover since the kernel has order 2.

For example, the 24-hour clock is a double cover of the 12-hour clock.

It has a non-algebraic double cover that is simply connected.

The subsemigroup of group elements that take the Siegel upper half plane into itself has a natural double cover.

It is possible for two different graphs to have isomorphic bipartite double covers.

He has contributed to domination number, bipartite double cover, and reconstruction theory.

Actually it is the double cover 2.

In particular the double cover has an irreducible 6-dimensional representation over the field of 3 elements.