Unlink

Look up unlink in Wiktionary, the free dictionary.

In the mathematical field of knot theory, an unlink is a link that is equivalent (under ambient isotopy) to finitely many disjoint circles in the plane.^[1]

The two-component unlink, consisting of two non-interlinked unknots, is the simplest possible unlink.

• An n-component link L ⊂ S³ is an unlink if and only if there exists n disjointly embedded discs D_i ⊂ S³ such that L = ∪_i∂D_i.
• A link with one component is an unlink if and only if it is the unknot.
• The
  Brunnian links
  .

• The Hopf link is a simple example of a link with two components that is not an unlink.
• The Borromean rings form a link with three components that is not an unlink; however, any two of the rings considered on their own do form a two-component unlink.
• Taizo Kanenobu has shown that for all n > 1 there exists a hyperbolic link of n components such that any proper sublink is an unlink (a Brunnian link). The Whitehead link and Borromean rings are such examples for n = 2, 3.^[1]

• Linking number