English

Knot polynomials from 1-cocycles

Geometric Topology 2019-01-17 v5

Abstract

Let MnM_n be the topological moduli space of all parallel n-cables of long framed oriented knots in 3-space. We construct in a combinatorial way for each natural number n>1n>1 a 1-cocycle RnR_n which represents a non trivial class in H1(Mn;Z[x1,x2,...,x11,x21,...])H^1(M_n; \mathbb{Z} [x_1,x_2,...,x_1^{-1},x_2^{-1},...]), where the number of variables xmx_m depends on nn. To each generic point in MnM_n we associate in a canonical way an arc {\em scan} in MnM_n, such that Rn(scan)R_n(scan) is already a polynomial knot invariant. We show that R3(scan)R_3(scan) detects the non-invertibility of the knot 8178_{17} in a very simple way and without using the knot group. There are two well-known canonical loops in MnM_n for each parallel n-cable of a long framed knot KK: Gramain's loop {\em rot} and the Fox-Hatcher loop {\em fh}. The calculation of RnR_n is of at most quartic complexity for these loops with respect to the number of crossings of KK for each fixed nn. It follows from results of Hatcher that KK is not a torus knot if the rational function Rn(fh(K))/Rn(rot(K))R_n(fh(K))/R_n(rot(K)) is not constant for each n>1n>1. nRn \oplus_n R_n is a natural candidate in order to separate all classes in H1(M1;Q)H1(Mn;Q)H_1(M_1;\mathbb{Q}) \cong H_1(M_n;\mathbb{Q}), and in particular to distinguish all knot types π0(M1)\pi_0(M_1).

Keywords

Cite

@article{arxiv.1709.10332,
  title  = {Knot polynomials from 1-cocycles},
  author = {Thomas Fiedler},
  journal= {arXiv preprint arXiv:1709.10332},
  year   = {2019}
}

Comments

The 1-cocycle is trivial

R2 v1 2026-06-22T21:58:45.546Z