Two-torsion in the grope and solvable filtrations of knots
Abstract
We study knots of order 22 in the grope filtration {𝒢h} and the solvable filtration {ℱh} of the knot concordance group. We show that, for any integer n≥4, there are knots generating a ℤ∞2 subgroup of 𝒢n/𝒢n.5. Considering the solvable filtration, our knots generate a ℤ∞2 subgroup of ℱn/ℱn.5(n≥2) distinct from the subgroup generated by the previously known 2-torsion knots of Cochran, Harvey, and Leidy. We also present a result on the 2-torsion part in the Cochran, Harvey, and Leidy’s primary decomposition of the solvable filtration.