Groups of the virtual trefoil and Kishino knots

摘要

In the paper [13], for an arbitrary virtual link L, three groups G(1, r) (L), r 0, G(2) (L) and G(3)(L) were defined. In the present paper, these groups for the virtual trefoil are investigated. The structure of these groups are found out and the fact that some of them are not isomorphic to each other is proved. Also, we prove that G(3) distinguishes the Kishino knot from the trivial knot. The fact that these groups have the lower central series which does not stabilize on the second term is noted. Hence, we have a possibility to study these groups using quotients by terms of the lower central series and to construct representations of these groups in rings of formal power series. It allows to construct an invariants for virtual knots.