3
$\begingroup$

It is well know that a 2 component link complement may doesn't detect the link type. My question is whether the following type of 2 component links detect their link types?

Such a link is composed of a knot with its meridian circle. Here its meridian circle means a meridian of the boundary of a solid torus neighborhood of the knot. Thank you.

$\endgroup$

1 Answer 1

6
$\begingroup$

I suppose that you are asking whether such links are determined by their complement. If this is the case, the answer is yes and it is a consequence of Gordon-Luecke's "knots are determinent by their complement" theorem.

The technique of a proof goes as follows. Since now "the complement of" means "the complement of an open tubolar neighborhood of". Let $K$ be a knot and $m$ an encircling meridian. We want to prove that $K\cup m$ is the only 2-component link having its complement. Gordon-Luecke says that the complement of $K$ is a compact manifold $M$ with one torus boundary, which has only one slope $s$ whose Dehn filling gives $S^3$.

The complement of $K\cup m$ is homeomorphic to the union $N=M\cup(P\times S^1)$ of $M$ and one copy of $P\times S^1$ where $P$ is the pair-of-pants. The fiber of $P\times S^1$ is glued to $M$ along the slope $s$. As usual with link complements, the problem of finding links in $S^3$ whose complement is $N$ translates into studying the Dehn fillings of $N$ giving $S^3$. By Gordon-Luecke, the only way to get $S^3$ is that $P\times S^1$ transforms into a solid torus with meridian $s$. One studies and easily classifies the fillings of $P\times S^1$ giving a solid torus with fiber-parallel meridian, and see that they all give rise to the same link.

$\endgroup$
2
  • $\begingroup$ @Bruno: Thank you. That is nice. So, by your last sentence, there are exactly two ways that the complement of K∪m is regarded as a link component (the complement of K∪m and m∪K ), right? Sorry, my English is poor, therefore maybe it is not so clear. But I guess that you know what I said. $\endgroup$
    – Bin Yu
    Commented Dec 2, 2011 at 15:36
  • $\begingroup$ Yes, exactly. If you use meridian-longitude coordinates for the two boundary tori of $P\times S^1$, the Dehn fillings that give a solid torus with fiber-parallel meridian are: $(1,q),(0,1)$, and $(0,1),(1,q')$. So you have two families of infinitely many fillings each. But the varying of $q$ or $q'$ actually does not affect the link. $\endgroup$ Commented Dec 2, 2011 at 18:35

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.