The writhe of a link, also called its twist number, is the sum of the signs of the link’s crossings. In short, it is the sum of the positive crossings minus the sum of the negative crossings. Note that the writhe is not an isotopy invariant and that is actually depends on the regular homotopy class of its projection.

Title writhe
Canonical name Writhe
Date of creation 2013-03-22 16:29:22
Last modified on 2013-03-22 16:29:22
Owner PrimeFan (13766)
Last modified by PrimeFan (13766)
Numerical id 6
Author PrimeFan (13766)
Entry type Definition
Classification msc 57M25
Synonym twist number