Bounds on alternating surgery slopes

McCoy, Duncan

doi:10.2140/agt.2017.17.2603

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Bounds on alternating surgery slopes

Duncan McCoy

Algebraic & Geometric Topology 17 (2017) 2603–2634

DOI: 10.2140/agt.2017.17.2603

Abstract

We show that if $p ∕ q$ –surgery on a nontrivial knot $K$ yields the branched double cover of an alternating knot, then $| p ∕ q | \leq 4 g (K) + 3$ . This generalises a bound for lens space surgeries first established by Rasmussen. We also show that all surgery coefficients yielding the double branched covers of alternating knots must be contained in an interval of width two and this full range can be realised only if the knot is a cable knot. The work of Greene and Gibbons shows that if $S_{p ∕ q}^{3} (K)$ bounds a sharp $4$ –manifold $X$ , then the intersection form of $X$ takes the form of a changemaker lattice. We extend this to show that the intersection form is determined uniquely by the knot $K$ , the slope $p ∕ q$ and the Betti number $b_{2} (X)$ .

Keywords

alternating knots, branched double covers, Dehn surgery

Mathematical Subject Classification 2010

Primary: 57M12, 57M25

Secondary: 57M27

References

Publication

Received: 15 December 2014

Revised: 27 February 2017

Accepted: 25 March 2017

Published: 19 September 2017

Authors

Duncan McCoy
Department of Mathematics University of Texas Austin, TX United States
http://www.ma.utexas.edu/users/d.mccoy/

Volume 17, issue 5 (2017)