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[parent] writhe (Definition)

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.




"writhe" is owned by PrimeFan. [ owner history (1) ]
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Other names:  twist number

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Cross-references: projection, class, homotopy, regular, invariant, isotopy, negative, positive, sum, link
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This is version 3 of writhe, born on 2006-12-22, modified 2007-02-05.
Object id is 8659, canonical name is Writhe.
Accessed 1645 times total.

Classification:
AMS MSC57M25 (Manifolds and cell complexes :: Low-dimensional topology :: Knots and links in $S^3$)

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