The (-2,3,7) Pretzel knot
K may be obtained by Dehn surgery on the
minimally twisted five chain link, MT5C.
K will be the core of one of
the surgery solid tori. It is also an embedded curve on the once-punctured
torus fiber of the trefoil knot. Viewing this fiber as the plumbing of two
Hopf bands,
K may be obtained by Dehn twisting the first core twice
about the second and then Dehn twisting this result twice about the original
first core.
Quotienting each of these constructions by an involution, we may view the
exterior of
K as a ball containing a 2-string tangle as the fixed
set of the involution. The presentation as a "punctured" 3-strand braid
naturally arises from each of these constructions.
On the left, the colored arcs suggest the tangles filling four of the boundary
components of the quotiented exterior of the MT5C. On the right, the colored
arcs taken in pairs suggest the tangles descending from the Dehn surgery
realization of the Dehn twists on the trefoil.
Below we plug the above tangle with three different rational tangles. Then we
perform isotopies to obtain two-bridge presentations of the resulting links.
In this manner we may observe how the exterior of
K admits the three
cyclic fillings
S^3,
L(18,5), and
L(19,7).