scholarly journals A Diagrammatic Approach for Determining the Braid Index of Alternating Links

2021 ◽  
Author(s):  
Yuanan Diao ◽  
Claus Ernst ◽  
Gabor Hetyei ◽  
Pengyu Liu
Keyword(s):  
Braid Index ◽  
Alternating Links

scholarly journals Braid index bounds ropelength from below

2020 ◽  
Vol 29 (04) ◽  
pp. 2050019
Author(s):  
Yuanan Diao
Keyword(s):  
Lower Bound ◽  
General Formula ◽  
Crossing Number ◽  
Crossing Numbers ◽  
Braid Index ◽  
Alternating Links

For an unoriented link [Formula: see text], let [Formula: see text] be the ropelength of [Formula: see text]. It is known that in general [Formula: see text] is at least of the order [Formula: see text], and at most of the order [Formula: see text] where [Formula: see text] is the minimum crossing number of [Formula: see text]. Furthermore, it is known that there exist families of (infinitely many) links with the property [Formula: see text]. A long standing open conjecture states that if [Formula: see text] is alternating, then [Formula: see text] is at least of the order [Formula: see text]. In this paper, we show that the braid index of a link also gives a lower bound of its ropelength. More specifically, we show that there exists a constant [Formula: see text] such that [Formula: see text] for any [Formula: see text], where [Formula: see text] is the largest braid index among all braid indices corresponding to all possible orientation assignments of the components of [Formula: see text] (called the maximum braid index of [Formula: see text]). Consequently, [Formula: see text] for any link [Formula: see text] whose maximum braid index is proportional to its crossing number. In the case of alternating links, the maximum braid indices for many of them are proportional to their crossing numbers hence the above conjecture holds for these alternating links.

scholarly journals The braid index of reduced alternating links

2019 ◽  
Vol 168 (3) ◽  
pp. 415-434
Author(s):  
YUANAN DIAO ◽  
GÁBOR HETYEI ◽  
PENGYU LIU
Keyword(s):  
Jones Polynomial ◽  
Link Diagram ◽  
Homfly Polynomial ◽  
Link Diagrams ◽  
Braid Index ◽  
Weight One ◽  
Minimum Number ◽  
Remarkable Result ◽  
Alternating Links ◽  
Alternating Link

AbstractIt is well known that the minimum crossing number of an alternating link equals the number of crossings in any reduced alternating link diagram of the link. This remarkable result is an application of the Jones polynomial. In the case of the braid index of an alternating link, Yamada showed that the minimum number of Seifert circles over all regular projections of a link equals the braid index. Thus one may conjecture that the number of Seifert circles in a reduced alternating diagram of the link equals the braid index of the link, but this turns out to be false. In this paper we prove the next best thing that one could hope for: we characterise exactly those alternating links for which their braid indices equal the numbers of Seifert circles in their corresponding reduced alternating link diagrams. More specifically, we prove that if D is a reduced alternating link diagram of an alternating link L, then b(L), the braid index of L, equals the number of Seifert circles in D if and only if GS(D) contains no edges of weight one. Here GS(D), called the Seifert graph of D, is an edge weighted simple graph obtained from D by identifying each Seifert circle of D as a vertex of GS(D) such that two vertices in GS(D) are connected by an edge if and only if the two corresponding Seifert circles share crossings between them in D and that the weight of the edge is the number of crossings between the two Seifert circles. This result is partly based on the well-known MFW inequality, which states that the a-span of the HOMFLY polynomial of L is a lower bound of 2b(L)−2, as well as the result of Yamada relating the minimum number of Seifert circles over all link diagrams of L to b(L).

Twisted torus knots T(mn + m + 1,mn + 1,mn + m + 2,−1) and T(n + 1,n,2n − 1,−1) are torus knots

2021 ◽  
pp. 2150016
Author(s):  
Sangyop Lee
Keyword(s):  
Torus Knots ◽  
Torus Knot ◽  
Braid Index

A twisted torus knot [Formula: see text] is a torus knot [Formula: see text] with [Formula: see text] adjacent strands twisted fully [Formula: see text] times. In this paper, we determine the braid index of the knot [Formula: see text] when the parameters [Formula: see text] satisfy [Formula: see text]. If the last parameter [Formula: see text] additionally satisfies [Formula: see text], then we also determine the parameters [Formula: see text] for which [Formula: see text] is a torus knot.

scholarly journals Almost alternating links

1992 ◽  
Vol 46 (2) ◽  
pp. 151-165 ◽  
Author(s):  
Colin C. Adams ◽  
Jeffrey F. Brock ◽  
John Bugbee ◽  
Timothy D. Comar ◽  
Keith A. Faigin ◽  
...  
Keyword(s):  
Alternating Links

scholarly journals On the Braid Index of Kanenobu Knots

2015 ◽  
Vol 55 (1) ◽  
pp. 169-180 ◽  
Author(s):  
Hideo Takioka
Keyword(s):  
Braid Index

On the braid index of links with nested diagrams

1992 ◽  
Vol 111 (2) ◽  
pp. 273-281 ◽  
Author(s):  
D. A. Chalcraft
Keyword(s):  
Lower Bound ◽  
Large Class ◽  
Upper Bound ◽  
Simple Criterion ◽  
Braid Index

AbstractThe number of Seifert circuits in a diagram of a link is well known 9 to be an upper bound for the braid index of the link. The -breadth of the so-called P-polynomial 3 of the link is known 5, 2 to give a lower bound. In this paper we consider a large class of links diagrams, including all diagrams where the interior of every Seifert circuit is empty. We show that either these bounds coincide, or else the upper bound is not sharp, and we obtain a very simple criterion for distinguishing these cases.

scholarly journals A FAMILY OF PSEUDO-ANOSOV BRAIDS WITH LARGE CONJUGACY INVARIANT SETS

2013 ◽  
Vol 22 (06) ◽  
pp. 1350025 ◽  
Author(s):  
BYUNG HEE AN ◽  
KI HYOUNG KO
Keyword(s):  
Invariant Sets ◽  
Braid Index

We show that there is a family of pseudo-Anosov braids independently parametrized by the braid index and the (canonical) length whose smallest conjugacy invariant sets grow exponentially in the braid index and linearly in the length.

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