Average crosscap number of a 2-bridge knot
Geometric Topology
2025-08-07 v2
Abstract
We determine a simple condition on a particular state graph of an alternating knot or link diagram that characterizes when the unoriented genus and crosscap number coincide, extending work of Adams and Kindred. Building on this same work and using continued fraction expansions, we provide a new formula for the unoriented genus of a 2-bridge knot or link. We use recursion to obtain exact formulas for the average unoriented genus and average crosscap number of all 2-bridge knots with crossing number , and in particular we show that .
Keywords
Cite
@article{arxiv.2501.03099,
title = {Average crosscap number of a 2-bridge knot},
author = {Moshe Cohen and Thomas Kindred and Adam M. Lowrance and Patrick D. Shanahan and Cornelia A. Van Cott},
journal= {arXiv preprint arXiv:2501.03099},
year = {2025}
}
Comments
Minor revisions of exposition