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Krzysztof Putyra, University of Zurich, An equivalence between gl(2)-foams and Bar-Natan cobordisms

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May 6 | 3:00 pm - 4:00 pm EDT

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The original construction of the Khovanov homology of a link can be seen as a formal complex in the category of flat tangles and surfaces between them. There is a way to associate a chain map with a link cobordism, but only up to a sign. Blanchet has fixed this by introducing the category of gl(2)-foams, certain singular cobordisms between planar trivalent graphs. Originating from the representation theory of quantum groups, foams are usually thought as algebraic objects. In my talk I will bring topology back by interpreting foams as two surfaces transverse to each other. This description leads to a quick proof that gl(2)-foams can be evaluated, a construction of a natural basis of foams, and an explicit equivalence between the category of gl(2)-foams and cobordisms between flat tangles [1]. An immediate application is a functorial version of the Chen-Khovanov tangle homology as well as of the quantized annular homology, constructed previously by Anna Beliakova, Stephan Wehrli, and me [2].

This is a joint work with Anna Beliakova, Matthew Hogancamp and Stephan Wehrli.

[1] arXiv:1903.12194
[2] arXiv:1605.03523



May 6

3:00 pm - 4:00 pm
Event Category:
SAS 4201