Ribbon theory
Ribbon theory is a strand of mathematics within topology that has seen particular application as regards DNA.
Concepts
Link is the integer number of turns of the ribbon around its axis;
Twist is the rate of rotation of the ribbon around its axis;
Writhe is a measure of non-planarity of the ribbon's axis curve.
Work by Călugăreanu, White and Brock Fuller led to the Călugăreanu–White–Fuller theorem that Link = Writhe + Twist.
See also
Bollobás–Riordan polynomial
Knots and graphs
Knot theory
DNA supercoil
References
Adams, Colin (2004), The Knot Book: An Elementary Introduction to the Mathematical Theory of Knots, American Mathematical Society, ISBN 0-8218-3678-1
Călugăreanu, G. 1959 'L’intégral de Gauss et l’analyse des nœuds tridimensionnels', Rev. Math. Pures Appl. 4, 5–20.
Călugăreanu, G. 1961 'Sur les classes d’isotopie des noeuds tridimensionels et leurs invariants', Czech. Math. J. 11, 588–625.
Fuller F. B. 1971 'The writhing number of a space curve', Proc Natl Acad Sci U S A. Apr;68(4):815–9.
