Braid Indices in a Class of Closed Braids

1 online resource (67 pages) : PDF

2010

University of North Carolina at Charlotte

A long-standing problem in knot theory concerns the additivity of crossing numbers of links under the connected sum operation. It is conjectured that if L1 and L2 are links, then Cr(L1#L2)=Cr(L1)+Cr(L2), but so far this has been proved only for certain classes of links. For example, in cases where both L1 and L2 are alternating or adequate links, the conjecture is known to be true. Another situation in which Cr(L1#L2)=Cr(L1)+Cr(L2) is when both L1 and L2 are zero-deficiency links. Zero-deficiency links include some but not all of the links in the prior named classes, as well as some links that are not included in either of those. In addition, further results are known for situations in which only one of the links being connected has deficiency zero. In this paper we expand the known realm of zero-deficiency links to include some cases of links represented by alternating closed braids. The ultimate goal is to show that if Dk is any k-string, reduced, alternating, closed braid, then the braid index of Dk is k. Herein we show the result for a certain subset of these closed braids, those with at most two sequences of crossings between consecutive strings in the braid. This result is proved using a property of the HOMFLY polynomial, which provides a lower bound for the braid index of a link. In the process, a simplified formulation for computing the HOMFLY polynomial is implemented. It seems likely that this result can be extended to prove the result for more complex alternating closed braids.

doctoral dissertations

Mathematics

Ph.D.

Braids
Closed Braids
HOMFLY
Knot Theory
Zero-Deficiency Links

Applied Mathematics

Diao, Yuanan

Houston, Evan
Hetyei, Gabor
Willis, Andrew

Thesis (Ph.D.)--University of North Carolina at Charlotte, 2010.

This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s). For additional information, see http://rightsstatements.org/page/InC/1.0/.

Copyright is held by the author unless otherwise indicated.

Hinson_uncc_0694D_10093

http://hdl.handle.net/20.500.13093/etd:329