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Knot theory is dealing with embedding of curves in manifolds of dimension 3. A knot is a single circle embedded in the affine space of dimension 3 as a smooth curve not crossing itself. Many knot invariants are known and can be used to distinguish knots.

7 votes
Accepted

Links with same Jones polynomial

Probably the best way to produce infinite families of links with same Jones polynomial is by Conway mutation, this operation does not alter the HOMFLY polynomial either. A good example of this is give …
Paolo Aceto's user avatar
6 votes
1 answer
480 views

Computations and applications of Khovanov's functor valued invariant of tangles

Soon after his famous paper "A categorification of the Jones polynomial", Khovanov introduced a "bordered" version. His theory assingns to every oriented even tangle a complex of (H_n,H_m)-bimodules, …
Paolo Aceto's user avatar
8 votes

Complexity of surfaces bounding knots in 4-ball and 3-sphere respectively

This is an answer to the first question. Let's indicate with $r(K)$ the ribbon number of a knot, i.e.the minimum number of ribbon singularities needed to realize a ribbon disc spanning $K$. We have $ …
Paolo Aceto's user avatar
6 votes
1 answer
2k views

Boundary links and ribbon links.

This question is about the relation between the notions of boundary link and ribbon link. For the definition of ribbon link see: ribbon links - counterexamples. An n-component link $L=L_1\cup\dots\c …
Paolo Aceto's user avatar
6 votes
1 answer
1k views

When is a connected sum of torus knots a slice knot?

This question is about the beaviour of 4-genus of knots with respect to connected sum. Let us indicate with $T(k)$ a Torus knot of type $(2,k)$, $k$ is an odd integer. Fix an orientation for every $T …
Paolo Aceto's user avatar
6 votes
1 answer
652 views

How to distinguish Pretzel links with the same coefficients?

Let $P:=P(a_1,\dots,a_n)$ be a Pretzel link ( https://en.wikipedia.org/wiki/Pretzel_link ). For every permutation $\sigma\in S_n$ we can consider the link $$\sigma P:=P(a_{\sigma(1)},\dots,a_{\sigma(n …
Paolo Aceto's user avatar
3 votes
0 answers
641 views

ribbon links - counterexamples

An n-component link is said to be ribbon if it bounds a ribbon surface consisting of n discs. (a ribbon surface is an immersed surface with only ribbon singularities, see http://en.wikipedia.org/wiki/ …
Paolo Aceto's user avatar
1 vote
2 answers
818 views

Trivial pretzel links

Is there a simple rule to check whether a pretzel link P(n_1,...,n_k) is a trivial link? I am interested in the 2-component case but every information would be helpful.
Paolo Aceto's user avatar
2 votes

Who thought that the Alexander polynomial was the only knot invariant of its kind?

You can find some historical remarks on polynomial invariants in chapter 9 of the book "Knots and links" by Cromwell, he also gives a lot of references.
Paolo Aceto's user avatar
2 votes
2 answers
1k views

Counting knots with fixed number of crossings

How to obtain an upperbound for knots up to k crossings? I think I've found something which involves the genus but I'm not sure.
Paolo Aceto's user avatar