# Jerusalem Mathematics Colloquium

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Thursday, 24th January 2002, 4:00 pm

Mathematics Building, Lecture Hall 2

The Jerusalem Mathematics Colloquium is happy to host the annual
Zabrodsky lecture. There are three lectures in the series, of which
this is the last. The other two are
Sunday Jan 20 14.00 Math 110:
"Knots and Functional Integration without integration"

Tuesday Jan 22 14.00 Math 209:
"Hopf algebras and Invariants of Links and Three-Manifolds"

##

Louis Kauffman

(University of Illinois at Chicago)

Virtual Knot Theory

** Abstract: **
Virtual knot theory is a generalization of classical knot theory. It
bears the same relationship to classical knots as graphs bear to
planar graphs. In representing a non-planar graph as a drawing in the
plane we need to introduce crossings of certain edges that are not
part of the graphical structure. These extra or virtual crossings are
"not really there." Just so, virtual knot and link diagrams have
crossings that are not really there. The virtual knots are represented
by diagrams and they stand for the oriented Gauss codes (or Gauss
diagrams) taken up to the equivalence relation generated by the
Reidemeister moves.

In studying virtual knots one gets to look at knot
theory in a new light. There are non-trivial virtual knots with unit
Jones polynomial and non-trivial fundamental group. There are virtual
knots with integer fundamental group and non-trivial Jones
polynomial. There are virtual knots whose knottedness is so far
undetected.

Virtual knots can be interpreted as knots in thickened
surfaces taken up to the addition and subtraction of empty
handles. This interpretation provides a direct connection of the
virtual theory with the realities of three-dimensional topology.

This
talk will introduce virtual knots and links and discuss the
construction of invariants, topological interpretations, examples and
open problems.

Coffee, Cookies at the faculty lounge at 3:30.

You are invited to join the speaker for further discussion after the
talk at Beit Belgia.

List of talks, 2001-02

List of talks, 2000-01

List of talks, 1998-99

List of talks, 1997-98