Biquandle Fares and Link Invariants
Sam Nelson, Stella Shah
TL;DR
This paper introduces biquandle fares, a new infinite family of invariants for oriented classical and virtual knots and links, built from path-like routes in biquandle-colored diagrams mapped into an abelian group. By defining fares of order $n$ and enforcing Reidemeister-move invariance, the authors obtain enhanced invariants in multiset or polynomial form, with detailed treatment of $n=1$ and $n=2$ cases, including complete, through, and crooked $2$-fares. They provide explicit examples demonstrating that these invariants can distinguish knots with identical biquandle counting invariants and show the computational viability via concrete computations. They also discuss decomposability of $2$-fares and raise questions about higher-order fares, potential homology-theoretic structures, and relationships to existing invariants such as biquandle brackets.
Abstract
We introduce a new family of invariants of oriented classical and virtual knots and links using fares, maps from paths in biquandle-colored diagrams to an abelian coefficient group. We consider the cases of 1-fares and 2-fares, provide examples to show that the enhancements are proper and end with some open questions about the cases of n-fares for n > 2.
