We introduce a notion of intrinsic linking and knotting for virtual spatial graphs. Our theory gives two filtrations of the set of all graphs, allowing us to measure, in a sense, how intrinsically linked or knotted a graph is; we show that these filtrations are descending and nonterminating. We also provide several examples of intrinsically virtually linked and knotted graphs. As a byproduct, we introduce the virtual unknotting number of a knot, and show that any knot with nontrivial Jones polynomial has virtual unknotting number at least 2.
Permission has been granted by Mathematical Sciences Publishers to supply this article for educational and research purposes. More info can be found about the Algebraic & Geometric Topology at http://msp.org/agt/about/journal/about.html. © Mathematical Sciences Publishers.
Fleming, T. and B. Mellor, 2007: Intrinsic Linking and Knotting in Virtual Spatial Graphs. Algebr. Geom. Topol., 7, 583-601.