Arnold's seminar, Moscow, May 17, 2005 Louis H Kauffman (UIC) Introduction to Virtual Knot Theory Abstract: Virtual knot theory is a stabilized theory of knots and links embedded in thickened surfaces (S x I where S is a surface of genus g). This theory has a diagrammatic expression very similar to the usual knot diagrams for knots in the three-sphere. In virtual knot theory one adds an extra crossing that is neither over nor under, and rules that are compatible with the above interpretation of the theory. In a sense, virtual knot theory is to classical knot theory as all graphs are to planar graphs. Many phenomena appear in the virtual theory that are quite different from the classical case. These include non-trivial knots with unit Jones polynomial. This talk is an introduction to the theory, and a discussion of problems, results and new invariants and new ideas that arise from this point of view. Many people have contributed to this field since its onset in 1996. We shall touch on their work! Here is a short list of the contributors: V.G. Bardakov, A. Bartholomew, S. Budden, S. Carter, D. Bar-Natan,H. Dye, R. Fenn, R. Furmaniak, M. Gousssarov, J. Green, D. Hrencecin, D. Jelsovsky, M. Jordan, L. Kauffman, T. Kadokami, N. Kamada, T. Kishino, G. Kuperberg, M. Saito, D. Silver, S. Kamada, S. Lambropoulou, S. Nelson, V. O. Manturov, D. E. Radford, M. Polyak, S. Satoh, J. Sawollek, W. Schellhorn, V.V. Vershinin, O. Viro, S. Williams, P. Zinn-Justin and J. B. Zuber. ------- http://www.pdmi.ras.ru/~arnsem