#### Volume 9, issue 3 (2009)

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Surgery on a knot in $(\mathrm{surface} \times I)$

### Martin Scharlemann and Abigail A Thompson

Algebraic & Geometric Topology 9 (2009) 1825–1835
##### Abstract

Suppose $F$ is a compact orientable surface, $K$ is a knot in $F×I$, and ${\left(F×I\right)}_{surg}$ is the $3$–manifold obtained by some nontrivial surgery on $K$. If $F×\left\{0\right\}$ compresses in ${\left(F×I\right)}_{surg}$, then there is an annulus in $F×I$ with one end $K$ and the other end an essential simple closed curve in $F×\left\{0\right\}$. Moreover, the end of the annulus at $K$ determines the surgery slope.

An application: Suppose $M$ is a compact orientable $3$–manifold that fibers over the circle. If surgery on $K\subset M$ yields a reducible manifold, then either

* the projection $K\subset M\to {S}^{1}$ has nontrivial winding number,

* $K$ lies in a ball,

* $K$ lies in a fiber, or

* $K$ is cabled.

##### Keywords
Dehn surgery, taut sutured manifold
Primary: 57M27
##### Publication
Received: 5 June 2009
Revised: 10 August 2009
Accepted: 11 August 2009
Published: 2 October 2009
##### Authors
 Martin Scharlemann Mathematics Department University of California, Santa Barbara Santa Barbara, CA 93117 USA http://www.math.ucsb.edu/~mgscharl/ Abigail A Thompson Mathematics Department University of California, Davis Davis, CA 95616 USA http://www.math.ucdavis.edu/~thompson/