Every knot or link K ⊂ S3 can be put in a bridge position with respect to a 2–sphere for some bridge number m ≥ m0, where m0 is the bridge number for K. Such m–bridge positions determine 2m–plat projections for the knot. We show that if m ≥ 3 and the underlying braid of the plat has n − 1 rows of twists and all the twisting coefficients have absolute values greater than or equal to three then the distance of the bridge sphere is exactly ⌈n∕(2(m − 2))⌉, where ⌈x⌉ is the smallest integer greater than or equal to x. As a corollary, we conclude that if such a diagram has n > 4m(m − 2) rows then the bridge sphere defining the plat projection is the unique, up to isotopy, minimal bridge sphere for the knot or link. This is a crucial step towards proving a canonical (thus a classifying) form for knots that are “highly twisted” in the sense we define.
Keywords: Heegaard splittings, bridge sphere, plats, bridge distance, train tracks
Johnson, Jesse  1 ; Moriah, Yoav  2
@article{10_2140_agt_2016_16_3361,
author = {Johnson, Jesse and Moriah, Yoav},
title = {Bridge distance and plat projections},
journal = {Algebraic and Geometric Topology},
pages = {3361--3384},
year = {2016},
volume = {16},
number = {6},
doi = {10.2140/agt.2016.16.3361},
url = {http://geodesic.mathdoc.fr/articles/10.2140/agt.2016.16.3361/}
}
TY - JOUR AU - Johnson, Jesse AU - Moriah, Yoav TI - Bridge distance and plat projections JO - Algebraic and Geometric Topology PY - 2016 SP - 3361 EP - 3384 VL - 16 IS - 6 UR - http://geodesic.mathdoc.fr/articles/10.2140/agt.2016.16.3361/ DO - 10.2140/agt.2016.16.3361 ID - 10_2140_agt_2016_16_3361 ER -
Johnson, Jesse; Moriah, Yoav. Bridge distance and plat projections. Algebraic and Geometric Topology, Tome 16 (2016) no. 6, pp. 3361-3384. doi: 10.2140/agt.2016.16.3361
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