THE SEMINAR

THEORY OF DUALITY

DEPARTMENT OF MATHEMATICAL METHODS IN PHYSICS



On the 16th of March 2017, at 10:15 a.m.

Józef H. Przytycki (The George Washington University)

will give a talk on

"Torsion in Khovanov homology"

Abstract
We recall the definition of the Khovanov homology of links and mention its modification to odd Khovanov homology. We discuss the fact that in Khovanov homology of links, presence of ℤ2-torsion is a very common phenomenon. We outline the several reasons for this observation (e.g., Hochschild homology of the algebra ℤ[x]/(x2), crucial in Khovanov homology, has only ℤ2 torsion). For other than ℤ2 torsion only a finite number of examples of knots with ℤn-torsion were known, none for n>8. In this talk, we show that there are infinite families of links whose Khovanov homology contains ℤn-torsion for 2 < n < 9 and ℤ2s-torsion for s < 24. We also introduce 4-braid links with ℤ3-torsion which are counterexamples to the PS braid conjecture. We mention that our construction also provides an infinite family of knots with ℤ5-torsion in reduced Khovanov homology and ℤ3-torsion in odd Khovanov homology. Most of our examples are twisted torus knots and links.

The seminar takes place on Thursdays from 10:15 a.m. to 12:00 in the room 2.23 of the main building of the Faculty of Physics (the 2nd floor), Pasteur Str. 5, Warszawa.
Additional information can be found on the webpage http://oldwww.fuw.edu.pl/KMMF/sem.czw.przedp.html.